Simple and Efficient Synthesis of Allyl Sulfones through Cs₂CO₃-Mediated Radical Sulfonylation of Morita–Baylis–Hillman Adducts with Thiosulfonates

Key words

allyl sulfones - cesium carbonate - MBH adducts - radical sulfonylation - thiosulfonates

Thiosulfonates (R¹SO₂-SR²)[1] have emerged as powerful reactants to synthesize many valuable organosulfur compounds.[2] Also known as sulfonothioates or S-esters of thiosulfonic acid, they generally show low toxicity. Typically, thiosulfonates serve as electrophilic sulfenylating reagents,[3] generating a sulfonyl moiety as by-product. Additionally, homolytic cleavage of the S–S(O₂) bond of thiosulfonates generates sulfonyl and sulfenyl radicals under thermal or photochemical conditions.[4] As a result, thiosulfonates have been utilized to install two distinct C–S bonds (sulfenyl and sulfonyl) through atom transfer thiosulfonylation.[5] Despite these achievements, thiosulfonates have rarely been explored as sulfonylating agents.[6]

On the other hand, allyl aryl sulfones are attractive intermediates in organic synthesis[7] and they are widely distributed pharmacophores,[8] for instance in anticancer agents,[8a] cysteine protease inhibitors,[8b] [c] TSH receptor antagonists,[8d] and antibacterial agents[8e] (Figure [1]). Therefore, the development of efficient and straightforward methods for the synthesis of allyl sulfones continues to attract considerable attention. In this context, various sulfonyl reagents[9] [10] (sulfinates,[9] arylsulfonyl cyanides,[10a] arenesulfonylmethyl isocyanide,[10b] and sulfinyl chlorides,[10c] sulfonyl hydrazines,[10d] and sulfinic acids[10e]) have been used for the sulfonylation of Morita–Baylis–Hillman (MBH) adducts for the synthesis of allyl sulfone derivatives (Scheme [1a]). Compared to these sulfonyl reactants, aryl thiosulfonates[1c] are usually stable crystalline solids, easy to handle and widely accessible starting precursors. Accordingly, we envisaged that thiosulfonates could be alternative starting materials to offer an opportunity for the synthesis of allyl sulfones. This fact motivated us to develop a possible new strategy for radical sulfonylation of Morita–Baylis–Hillman (MBH) adducts under mild conditions (Scheme [1b]). Of note, the multifunctional MBH allyl bromides and MBH acetates can be easily prepared and have been widely studied.[11] As part of our ongoing research programme on organosulfur chemistry[12] and the utilization of thiosulfonates,[3c] [d] [5e] [6c] [12b] [c] we report herein a simple and efficient radical sulfonylation of MBH allyl bromides/acetates with thiosulfonates in the presence of Cs₂CO₃ to access a range of (hetero)aryl/alkyl allyl sulfones. To our knowledge, radical sulfonylation using thiosulfonates has not been previously explored.[6`] [d] [e]

Figure 1 Representative biologically active allyl sulfones

Scheme 1 Allyl sulfonylation of MBH adducts using various sulfonyl reagents

At the outset, our optimization investigations began with S-phenyl benzenesulfonothioate (1a) and (Z)-methyl 2-(bromomethyl)-3-phenylacrylate (2a) as model substrates (Table [1]). Initially, the reaction between 1a and 2a in a 1:1.5 ratio in the presence of Cs₂CO₃ in EtOH provided the allyl sulfone 3aa in 65% yield (entry 1). On reversing the ratios of 1a and 2a (1.5:1) the desired product 3aa was produced in 79% yield (entry 2). Various solvents, such as DMF, CH₃CN, 1,4-dioxane, DMSO and toluene were screened (entries 3–7). Among these solvents, CH₃CN proved the best choice for the transformation, giving 3aa in 80% yield (entry 4). In CH₃CN at 80 °C, the yield of the reaction between 1a, 2a and Cs₂CO₃ (1:1.5:2 ratio) was improved considerably, giving 3aa in 91% yield (entry 8). To our satisfaction, use of 1 equiv of Cs₂CO₃ provided the desired allyl sulfone (3aa) in 96% yield (entry 9). Using 1.2 equiv of 2a or 1.5 equiv of Cs₂CO­₃ or performing the reaction at room temperature were not beneficial (entries 10–12).

Table 1 Optimization for the Sulfonylation of MBH Bromide with Thiosulfonate^a

Entry	1a (equiv)	2a (equiv)	Base (equiv)	Solvent	Temp (°C)	Time (h)	Yield of 3aa (%)b
1	1.0	1.5	Cs2CO3 (2.0)	EtOH	90	6	65
2	1.5	1.0	Cs2CO3 (2.0)	EtOH	90	6	79
3	1.5	1.0	Cs2CO3 (2.0)	DMF	90	6	47
4	1.5	1.0	Cs2CO3 (2.0)	CH3CN	80	5	80
5	1.5	1.0	Cs2CO3 (2.0)	dioxane	80	5	32
6	1.5	1.0	Cs2CO3 (2.0)	DMSO	90	6	47
7	1.5	1.0	Cs2CO3 (2.0)	toluene	90	6	25
8	1.0	1.5	Cs2CO3 (2.0)	CH3CN	80	4	91
9	1.0	1.5	Cs2CO3 (1.0)	CH3CN	80	4	96
10	1.0	1.2	Cs2CO3 (1.0)	CH3CN	80	5	79
11	1.0	1.5	Cs2CO3 (1.5)	CH3CN	80	4	91
12	1.0	1.5	Cs2CO3 (1.0)	CH3CN	rt	8	33
13	1.0	1.5	K2CO3 (1.0)	CH3CN	80	5	60
14	1.0	1.5	Na2CO3 (1.0)	CH3CN	80	8	trace
15	1.0	1.5	DABCO (1.0)	CH3CN	80	8	NR
16	1.0	1.5	–c	CH3CN	80	8	NR

^a All reactions were carried out on a 0.2 mmol scale.

^b Isolated yields.

^c Without Cs₂CO₃.

We then examined other bases (K₂CO₃, Na₂CO₃ and DABCO) but all afforded diminished yields (Table [1], entries 13–15). No reaction was observed in the absence of Cs₂CO₃, indicating that it plays a vital role in the sulfonylation process (entry 16). Only sulfonylated 3aa was obtained in all cases; the other anticipated allyl thioether (3aa′) did not form, probably due to the lower stability of the thiyl radical (ArS^•).[13]

Scheme 2 Substrate scope for the synthesis of allyl sulfones via radical sulfonylation of MBH bromides with thiosulfonates. Reagents and conditions (performed on a 0.5 mmol scale of thiosulfonate): 1 (1.0 equiv), MBH bromide 2 (1.5 equiv), Cs₂CO₃ (1.0 equiv) in MeCN (2.5 mL) at 80 °C. Isolated yields are given. Z/E ratio based on ¹H NMR analysis.

With the reaction conditions optimized, we then explored a broad range of thiosulfonates (1a–i) and MBH allyl bromides (2a–n) to furnish a series of allyl sulfones (3aa–i and 3ab–n) in good to excellent yields and stereoselectivities (Scheme [2]). Various alkyl and halo-substituted thiosulfonates (1a–f) reacted smoothly with 2a, providing the corresponding allyl sulfones 3aa–fa in 69–95% yields; an exception was 4-bromophenyl thiosulfonate (1f), which afforded moderate yields. In addition, 1/2-naphthyl and thiophenyl derived thiosulfonates 1g–i also served as suitable substrates to furnish the expected allyl sulfones in high yields. A variety of para-, meta- and ortho-substituted allyl bromides 2b–g were readily sulfonylated with 1a to give the anticipated allyl sulfones in 57–96% yields. The position and electronic nature of substituents on the phenyl ring of MBH bromides had a limited effect on this sulfonylation process. Additionally, different heteroaryl allyl sulfones 3ah–aj were produced in satisfactory yields from the corresponding allyl bromides. Interestingly, the alkenyl and alkyl-substituted MBH bromides 2k–m reacted well with 1a, giving the synthetically useful alkyl allyl sulfones in acceptable yields. The substrate scope was further extended to ethyl acrylate derived MBH bromide 2n, and the corresponding products 3an and 3bn were obtained in 96% and 98% yield, respectively.

Inspired by these results, we sought to evaluate the scope of MBH acetates 4 with S-aryl arylsulfonothioate (1a/b). Under the same conditions, acetate 4a was smoothly sulfonated with S-aryl arylsulfonothioate (1a/b), to give the desired products 3aa and 3ba in 86% and 81% yields, respectively, with slightly inferior stereoselectivities as compared to the allyl bromides (Scheme [3]).[14] Several aryl and heteroaryl derived substrates (4b,d,e,h–j) reacted well with 1a to form expected products (3ab,d,e,h–j) in reasonable yields. Similarly, the alkyl sulfones 3al and 3am were obtained in 69% and 79% yield, respectively, from the corresponding MBH acetates 4l/m under the standard conditions. It is worth noting that these allyl sulfones, particularly allyl (hetero)aryl sulfones, show activity against cancer and abnormal cell proliferation activity.[8a] The E/Z stereochemistry of the allyl sulfones was assigned based on the ¹H NMR chemical shift values of the olefinic protons as compared with the reported values.[15]

Scheme 3 Substrate scope for the synthesis of allyl sulfones via radical sulfonylation of MBH acetates with thiosulfonates. Reagents and conditions (performed on a 0.5 mmol scale of thiosulfonates): 1 (1.0 equiv), MBH acetate 4 (1.5 equiv), Cs₂CO₃ (1.0 equiv) in MeCN (2.5 mL) at 80 °C. Isolated yield are given. Z/E ratio based on ¹H NMR analysis.

Furthermore, the scope of the sulfonylation reaction could be extended to other representative classes of allyl bromides, such as acrylonitrile derived MBH allyl bromide (2o) or cinnamyl bromide (2p), as presented in Scheme [4]. Disappointingly, they did not provide the desired allyl sulfones 3ao and 3ap under the same conditions.

Scheme 4 Study of other allyl bromides 2o/p and gram-scale synthesis

The efficacy of radical sulfonylation was demonstrated at gram-scale under the optimal conditions (see the Supporting Information). Thus, a 5 mmol scale reaction of S-phenyl benzenesulfonothioate (1a) (1.25 g) and (Z)-methyl 2-(bromomethyl)-3-phenylacrylate (2a) (1.90 g) gave 3aa in 72% yield (1.14 g). Similarly, allyl sulfone 3aj was obtained in 78% yield (1.25 g) from acetate 4j. Thus, the protocol is scalable with little deviation of the outcome (Scheme [4]).

Several control experiments were performed to gain insight into the reaction mechanism (Scheme [5]). The standard reaction was performed with radical scavengers (BHT or TEMPO), in an attempt to define whether the reaction involved an ionic or radical pathway. With BHT, the product 3aa formed in <10% yield; whereas the reaction was totally inhibited with TEMPO (Scheme [5] i). These experiments suggest the process involves a radical sulfonylation pathway and this is in keeping with the known homolytic cleavage of thiosulfonate 1a to generate sulfonyl radical (I) and thiyl radical (II)[13] species (Scheme [5] ii).[4] Based on the above results and on literature precedent,[4] [6] [13] a plausible mechanism is proposed for this transformation (Scheme [5]). The radical initiation of PhSSO₂Ph (1a)[6d] [e] may lead to sulfonyl radical (I) and thiyl radical (II) in the presence of Cs₂CO₃. Subsequent propagation of 2a will form allyl radical (A) and termination product sulfonyl bromide (PhSO₂Br).[16] Finally, the termination product triggers the sulfonylation of A with PhSO₂Br to give the expected allyl sulfone 3aa. Similarly, sulfonyl radical can add onto MBH acetate to form radical B and eliminate an acetyl radical to afford the desired allyl sulfone 3aa. Overall, in this process, the Cs₂CO₃ might be playing a dual role as a radical initiator and as a base to trap the bromine radical.

Scheme 5 Control experiments and a plausible mechanism

In conclusion, we have described the Cs₂CO₃-promoted radical sulfonylation of Morita–Baylis–Hillman (MBH) bromides with thiosulfonates under mild conditions. A series of allyl sulfones was readily generated in good to high yields with high stereoselectivities. Various aryl, heteroaryl, alkenyl and alkyl MBH bromides/acetates and aryl/hetereoaryl thiosulfonates with diverse substitution patterns and broad functional group compatibility were elaborated. Furthermore, the MBH acetates efficiently furnished the corresponding allyl sulfones in high yields. The protocol was proven to be applicable to gram-scale synthesis, which can be challenging with other approaches. A plausible mechanism is presented to rationalize the experimental outcome.

Synthesis of Allyl Sulfones; General Procedure 1 (GP1)

A heat gun-dried Schleck tube was charged with thiosulfonate (0.5 mmol, 1.0 equiv), Morita–Baylis–Hillman allyl bromide (0.75 mmol, 1.5 equiv) or Morita–Baylis–Hillman acetate (0.75 mmol, 1.5 equiv) and Cs₂CO₃ (0.5 mmol, 1.0 equiv) in CH₃CN (2.5 mL). The reaction mixture was stirred at 80 °C for 4 h and monitored by TLC until the reaction was judged to be either complete or to be proceeding no further. The reaction was quenched by addition of water (10 mL) followed by extraction with EtOAc (3 × 20 mL). The combined organic layers were washed with brine (2 × 10 mL), dried over anhydrous Na₂SO­₄, filtered and the solvent was removed under reduced pressure. The resulting residue was subjected to flash chromatography (silica gel, eluting with 10–20% EtOAc/petroleum ether) to afford the desired allyl sulfones.

Methyl (Z)-3-Phenyl-2-[(phenylsulfonyl)methyl]acrylate (3aa)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-phenylacrylate 2a (191.3 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded the title compound 3aa.

Yield: 150.3 mg (95%); colorless solid; mp 63–65 °C (Lit.[6] 64–66 °C); R_f = 0.38 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>97:3) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.95 (s, 1 H), 7.85 (dd, J = 8.4, 1.2 Hz, 2 H), 7.60 (tt, J = 7.4, 1.2 Hz, 1 H), 7.52–7.46 (m, 4 H), 7.39–7.35 (m, 3 H), 4.49 (s, 2 H), 3.59 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.9, 146.5, 139.3, 133.8, 133.7, 129.8, 129.2 (2C), 129.1 (2C), 128.8 (2C), 128.6 (2C), 120.9, 55.2, 52.5.

The title compound is known in the literature and the data are consistent with reported values.[10e]

Methyl (Z)-3-Phenyl-2-(tosylmethyl)acrylate (3ba)

Obtained by following GP1 using S-(p-tolyl) 4-methylbenzenesulfonothioate 1b (139.1 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-phenylacrylate 2a (191.3 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded the title compound 3ba.

Yield: 145.4 mg (88%); colorless liquid R_f = 0.50 (20% EtOAc in petroleum ether); mixture of Z/E isomers (75:25) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.83 (s, 1 H), 7.61 (d, J = 8.3 Hz, 2 H), 7.38–7.35 (m, 2 H), 7.29–7.26 (m, 3 H), 7.17 (d, J = 8.0 Hz, 2 H), 4.38 (s, 2 H), 3.52 (s, 3 H), 2.32 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 167.1, 146.5, 146.2, 144.8, 136.4, 133.8, 129.8, 129.7 (2C), 129.3, 129.1, 128.9, 128.8, 128.6, 121.2, 55.2, 52.5, 21.7.

The title compound is known in the literature and the data are consistent with reported values.[9a] [10d]

Methyl (Z)-2-{[(4-(tert-Butyl)phenyl)sulfonyl]methyl}-3-phenyl­acrylate (3ca)

Obtained by following GP1 using S-(4-(tert-butyl)phenyl) 4-(tert-butyl­benzenesulfonothioate 1c (128.5 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-phenylacrylate 2a (191.3 mg, 0.75 mmol), and Cs₂CO­₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded title­ compound 3ca.

Yield: 128.3 mg (69%); colorless solid; mp 100–102 °C; R_f = 0.42 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>99:1) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.93 (s, 1 H), 7.76 (dt, J = 8.6, 2.0 Hz, 2 H), 7.50 (dt, J= 8.8, 2.1 Hz, 2 H), 7.48–7.45 (m, 2 H), 7.39–7.34 (m, 3 H), 4.48 (s, 2 H), 3.57 (s, 3 H), 1.34 (s, 9 H).

¹³C NMR (101 MHz, CDCl₃): δ = 167.1, 157.8, 146.3, 136.3, 133.8, 129.8, 129.3 (2C), 128.9 (2C), 128.6 (2C), 126.1 (2C), 121.2, 55.2, 52.4, 35.4, 31.2 (3C).

LCMS (ESI): m/z 373.00 [M + H]⁺.

Methyl (Z)-2-{[(4-Fluorophenyl)sulfonyl]methyl}-3-phenyl­acrylate (3da)

Obtained by following GP1 using S-(4-fluorophenyl)4-fluorobenzenesulfonothioate 1d (143.1 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-phenylacrylate 2a (191.3 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded title compound 3da.

Yield: 133.8 mg (80%); colorless solid; mp 72–74 °C; R_f = 0.37 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>97:1) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.93 (s, 1 H), 7.85–7.78 (m, 2 H), 7.45–7.41 (m, 2 H), 7.39–7.35 (m, 3 H), 7.12 (t, J = 8.5 Hz, 2 H), 4.50 (s, 2 H), 3.66 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.0 (d, J = 256.4 Hz), 166.9, 146.5, 135.3 (d, J = 3.1 Hz), 133.7, 131.5 (d, J = 9.7 Hz), 129.9, 129.2 (3C), 128.9 (3C), 120.9, 116.4 (d, J = 22.6 Hz), 55.1, 52.6.

LCMS (ESI): m/z 334.90 [M]⁺.

Methyl (Z)-2-{[(4-Chlorophenyl)sulfonyl]methyl}-3-phenyl­acrylate (3ea)

Obtained by following GP1 using S-(4-chlorophenyl)-4-chlorobenzenesulfonothioate 1e (175.4 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-phenylacrylate 2a (191.3 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded title compound 3ea.

Yield: 136.8 mg (78%); colorless solid; mp 86–88 °C; R_f = 0.35 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>97:3) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.92 (s, 1 H), 7.71 (dt, J = 8.6, 1.9 Hz, 2 H), 7.41–7.35 (m, 7 H), 4.51 (s, 2 H), 3.66 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.9, 146.5, 140.7, 137.6, 133.6, 130.1 (2C), 129.8, 129.4 (2C), 129.1 (2C), 128.9 (2C), 120.9, 55.0, 52.6.

LCMS (ESI): m/z 351.90 [M + H]⁺.

Methyl (Z)-2-{[(4-Bromophenyl)sulfonyl]methyl}-3-phenyl­acrylate (3fa)

Obtained by following GP1 using S-(4-bromophenyl)-4-bromobenzenesulfonothioate 1f (204.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-phenylacrylate 2a (191.3 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded title compound 3fa.

Yield: 136.3 mg (69%); yellow solid; mp 99–101 °C; R_f = 0.33 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>98:2) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.93 (s, 1 H), 7.64 (dt, J = 8.7, 2.0 Hz, 2 H), 7.57 (dt, J = 8.7, 2.0 Hz, 2 H), 7.40–7.36 (m, 5 H), 4.51 (s, 2 H), 3.67 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.9, 146.6, 138.0, 133.6, 132.4 (2C), 130.2 (2C), 129.9, 129.3, 129.1 (2C), 128.9 (2C), 120.8, 54.9, 52.7.

The title compound has been reported in the literature and the data are consistent with reported values.[10d]

Methyl (Z)-2-[(Naphthalen-1-ylsulfonyl)methyl]-3-phenyl­acrylate (3ga)

Obtained by following GP1 using S-(naphthalen-1-yl) naphthalene-1-sulfonothioate 1g (175.2 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-phenylacrylate 2a (191.3 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol), for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded title compound 3ga.

Yield: 144.6 mg (79%); colorless solid; mp 119–121 °C; R_f = 0.35 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>95:5) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 8.28 (s, 1 H), 7.84–7.77 (m, 4 H), 7.69 (dd, J = 8.7, 1.7 Hz, 1 H), 7.56 (t, J = 7.5 Hz, 1 H), 7.50 (t, J = 7.5 Hz, 1 H), 7.27 (d, J = 7.8 Hz, 2 H), 7.17–7.11 (m, 3 H), 4.47 (s, 2 H), 3.36 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.9, 146.3, 136.2, 135.4, 133.6, 132.1, 130.5, 129.6, 129.5, 129.4, 129.3, 129.0 (2C), 128.7 (2C), 128.0, 127.6, 123.2, 121.1, 55.1, 52.4.

LCMS (ESI): m/z 366.95 [M]⁺.

Methyl (Z)-2-((Naphthalen-2-ylsulfonyl)methyl)-3-phenyl­acrylate (3ha)

Obtained by following GP1 using S-(naphthalen-2-yl) naphthalene-2-sulfonothioate 1h (175.2 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-phenylacrylate 2a (191.3 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded title compound 3ha.

Yield: 141.2 mg (77%); colorless solid; mp 116–118 °C; R_f = 0.37 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>95:5) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 8.27 (s, 1 H), 7.84–7.77 (m, 4 H), 7.69 (d, J = 8.5 Hz, 1 H), 7.56 (t, J = 7.5 Hz, 1 H), 7.50 (t, J = 7.5 Hz, 1 H), 7.29–7.25 (m, 2 H), 7.14 (d, J = 7.4 Hz, 3 H), 4.47 (s, 2 H), 3.34 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.6, 146.0, 135.7, 135.0, 133.2, 131.7, 130.1, 129.3, 129.1, 129.04, 128.96, 128.7 (2C), 128.3 (2C), 127.6, 127.3, 122.8, 120.7, 54.7, 52.0.

LCMS (ESI): m/z 366.95 [M]⁺.

Methyl (Z)-3-Phenyl-2-[(thiophen-2-ylsulfonyl)methyl]acrylate (3ia)

Obtained by following GP1 using S-(thiophen-2-yl) thiophene-2-sulfonothioate 1i (115.1 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-phenylacrylate 2a (191.3 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded title compound 3ia.

Yield: 130.6 mg (81%); colorless liquid; R_f = 0.37 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>93:7) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.99 (s, 1 H), 7.67 (dd, J = 5.0, 1.3 Hz, 1 H), 7.60 (dd, J = 3.8, 1.3 Hz, 1 H), 7.47 (dd, J = 6.4, 3.1 Hz, 2 H), 7.39–7.36 (m, 3 H), 7.08 (dd, J = 5.0, 3.8 Hz, 1 H), 4.59 (s, 2 H), 3.67 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.9, 146.7, 140.0, 134.9, 134.7, 133.6, 129.8, 129.2 (2C), 128.8 (2C), 127.9, 120.8, 56.2, 52.6.

LCMS (ESI): m/z 322.90 [M]⁺.

Methyl (Z)-3-(4-Chlorophenyl)-2-[(phenylsulfonyl)methyl]acrylate­ (3ab)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol) methyl (Z)-2-(bromomethyl)-3-(4-chlorophenyl) acrylate 2b (217.1 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol), for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded the title compound 3ab.

Yield: 157.8 mg (90%); liquid; R_f = 0.20 (30% EtOAc in petroleum ether); mixture of Z/E isomers (>95:5) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.88 (s, 1 H), 7.84 (dd, J = 8.3, 1.0 Hz, 2 H), 7.62 (t, J = 7.5 Hz, 1 H), 7.50 (t, J = 7.8 Hz, 2 H), 7.45 (d, J = 8.5 Hz, 2 H), 7.34 (d, J = 8.5 Hz, 2 H), 4.43 (s, 2 H), 3.57 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.7, 145.1, 139.4, 136.0, 134.0, 132.2, 130.7 (2C), 129.20 (2C), 129.17 (2C), 128.6 (2C), 121.5, 55.2, 52.6.

The title compound is known in the literature and the data are consistent with reported values.[9f]

Methyl (Z)-2-[(Phenylsulfonyl)methyl]-3-(p-tolyl)acrylate (3ac)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-(p-tolyl)acrylate 2c (201.8 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded the title compound.

Yield: 132.1 mg (80%); colorless liquid; R_f = 0.29 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>96:4) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.92 (s, 1 H), 7.86 (dd, J = 8.3, 1.1 Hz, 2 H), 7.60 (tt, J = 7.4, 1.2 Hz, 1 H), 7.49 (t, J = 7.7 Hz, 2 H), 7.43 (d, J = 8.1 Hz, 2 H), 7.18 (d, J = 8.0 Hz, 2 H), 4.50 (s, 2 H), 3.54 (s, 3 H), 2.36 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 167.1, 146.6, 140.3, 139.4, 133.8, 130.9, 129.6 (2C), 129.5 (2C), 129.1 (2C), 128.6 (2C), 119.7, 55.3, 52.4, 21.5.

The title compound is known in the literature and the data are consistent with reported values.[10e]

Methyl (Z)-3-(4-Isopropylphenyl)-2-[(phenylsulfonyl)methyl]acrylate­ (3ad)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-(4-isopropylphenyl)acrylate 2d (222.8 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol), for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded title compound 3ad.

Yield: 102.1 mg (57%); colorless liquid; R_f = 0.39 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>98:2) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.93 (s, 1 H), 7.86 (dd, J = 8.4, 1.2 Hz, 2 H), 7.60 (tt, J = 7.4, 1.2 Hz, 1 H), 7.51–7.45 (m, 4 H), 7.24 (d, J = 8.2 Hz, 2 H), 4.52 (s, 2 H), 3.56 (s, 3 H), 2.91 (sept, J = 6.9 Hz, 1 H), 1.25 (d, J = 6.9 Hz, 6 H).

¹³C NMR (101 MHz, CDCl₃): δ = 167.2, 151.2, 146.7, 139.5, 133.8, 131.3, 129.7 (2C), 129.1 (2C), 128.7 (2C), 127.1 (2C), 119.8, 55.4, 52.4, 34.1, 23.9 (2C).

LCMS (ESI) m/z 359.00 [M + H]⁺.

Methyl (Z)-3-(3-Bromophenyl)-2-[(phenylsulfonyl)methyl]acrylate­ (3ae)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-(3-bromophenyl)acrylate 2e (239.9 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded title compound 3ae.

Yield: 189.7 mg (96%); pale-yellow solid; mp 64–66 °C; R_f = 0.29 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>95:5) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.96 (s, 1 H), 7.84 (dd, J = 8.3, 1.1 Hz, 2 H), 7.64–7.60 (m, 2 H), 7.57 (dd, J = 8.0, 1.1 Hz, 1 H), 7.50 (t, J = 7.7 Hz, 2 H), 7.35 (td, J = 7.5, 0.9 Hz, 1 H), 7.22 (td, J = 7.6, 1.4 Hz, 1 H), 4.36 (s, 2 H), 3.62 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.3, 145.3, 139.4, 134.1, 133.9, 133.0, 130.8, 130.1, 129.2 (2C), 128.5 (2C), 127.7, 124.1, 122.8, 55.0, 52.6.

The title compound is known in the literature and the data are consistent with reported values.[9f]

Methyl (Z)-3-(3-Methoxyphenyl)-2-[(phenylsulfonyl)methyl]acrylate­ (3af)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-(3-methoxyphenyl)acrylate 2f (213.8 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 20% EtOAc in petroleum ether) yielded title compound 3af.

Yield: 141.0 mg (80%); liquid; R_f = 0.42 (30% EtOAc in petroleum ether); mixture of Z/E isomers (83:17) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.88 (s, 1 H), 7.80 (d, J = 8.0 Hz, 2 H), 7.56 (t, J = 7.9 Hz, 1 H), 7.44 (t, J = 7.0 Hz, 2 H), 7.23 (t, J = 8.0 Hz, 1 H), 7.09 (s, 1 H), 6.98 (d, J = 7.5 Hz, 1 H), 6.87 (d, J = 8.0 Hz, 1 H), 4.46 (s, 2 H), 3.78 (s, 3 H), 3.54 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.7, 159.7, 146.2, 139.3, 134.8, 133.7, 129.7, 129.0 (2C), 128.4 (2C), 121.5, 121.0, 115.9, 113.9, 55.4, 55.2, 52.3.

LCMS (ESI): m/z 346.95 [M]⁺.

Methyl (Z)-3-(2-Bromophenyl)-2-[(phenylsulfonyl)methyl]acrylate­ (3ag)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-(2-bromophenyl)acrylate 2g (239.9 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded title compound 3ag.

Yield: 158.1 mg (80%); colorless solid; mp 110–112 °C; R_f = 0.27 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>95:5) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.85–7.79 (m, 3 H), 7.63 (tt, J = 7.4, 1.2 Hz, 1 H), 7.51–7.45 (m, 3 H), 7.44 (s, 1 H), 7.41 (dd, J = 7.7, 0.7 Hz, 1 H), 7.24 (t, J = 7.8 Hz, 1 H), 4.44 (s, 2 H), 3.65 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.5, 144.4, 138.9, 135.7, 134.0, 132.5, 131.9, 130.8, 129.2 (2C), 128.5 (2C), 127.4, 122.9, 122.5, 54.8, 52.7.

The title compound is reported in the literature and the data are consistent with reported values.[10a]

Methyl (Z)-2-((Phenylsulfonyl)methyl)-3-(thiophen-2-yl)acrylate (3ah)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-(thiophen-2-yl)acrylate 2h (185.0 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded the title compound 3ah.

Yield: 151.5 mg (94%); colorless liquid; R_f = 0.39 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>98:2) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 8.04 (s, 1 H), 7.89 (d, J = 8.2 Hz, 2 H), 7.59 (t, J = 7.4 Hz, 1 H), 7.53–7.47 (m, 4 H), 7.08 (t, J = 3.9 Hz, 1 H), 4.62 (s, 2 H), 3.51 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.8, 139.5, 138.3, 136.8, 134.3, 133.9, 131.0, 129.0 (2C), 128.7 (2C), 127.9, 116.2, 56.0, 52.4.

The title compound is reported in the literature and the data are consistent with reported values.[10a]

Methyl (Z)-2-((Phenylsulfonyl)methyl)-3-(1-tosyl-1H-indol-2-yl)-acrylate (3ai)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-(1-tosyl-1H-indol-2-yl)acrylate 2i (336.2 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 20% EtOAc in petroleum ether) yielded the title compound 3ai.

Yield: 198.7 mg (78%); colorless solid; mp 137–139 °C; R_f = 0.31 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>94:6) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 8.57 (s, 1 H), 8.09 (s, 1 H), 8.03 (d, J = 8.3 Hz, 1 H), 7.98 (d, J = 7.2 Hz, 2 H), 7.89 (d, J = 8.4 Hz, 2 H), 7.62 (tt, J = 7.4, 2.1 Hz, 1 H), 7.58–7.52 (m, 3 H), 7.41–7.36 (m, 1 H), 7.32–7.26 (m, 3 H), 4.51 (s, 2 H), 3.63 (s, 3 H), 2.35 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.6, 145.7, 139.6, 136.0, 134.9, 134.7, 134.0, 130.3 (2C), 130.0, 129.3 (2C), 128.6 (2C), 127.5, 127.3 (2C), 125.7, 124.0, 119.9, 119.3, 115.9, 113.9, 56.8, 52.6, 21.7.

LCMS (ESI): m/z 509.90 [M]⁺.

Methyl (Z)-3-(2-Chloroquinolin-3-yl)-2-[(phenylsulfonyl)methyl]-acrylate (3aj)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-3-(2-chloroquinolin-3-yl)acrylate 2j (254.1 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 20% EtOAc in petroleum ether) yielded the title compound 3aj.

Yield: 162.6 mg (81%); colorless solid; mp 129–13 °C; R_f = 0.21 (20% EtOAc in petroleum ether); mixture of Z/E isomers (80:20) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 8.74 (s, 1 H), 8.09 (s, 1 H), 8.04 (d, J = 8.5 Hz, 1 H), 7.95 (d, J = 7.7 Hz, 1 H), 7.90 (d, J = 7.3 Hz, 2 H), 7.80 (t, J = 7.7 Hz, 1 H), 7.65 (t, J = 6.9 Hz, 2 H), 7.53 (t, J = 7.7 Hz, 2 H), 4.36 (s, 2 H), 3.63 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.2, 148.3, 143.3, 139.5, 139.3, 138.7, 134.2, 131.8, 129.4 (2C), 128.7, 128.6 (2C), 128.5, 128.4, 128.0, 126.9, 124.0, 55.6, 52.9.

LCMS (ESI): m/z 401.80 [M]⁺.

Methyl (2Z,4E)-5-Phenyl-2-[(phenylsulfonyl)methyl]penta-2,4-dienoate (3ak)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (2Z,4E)-2-(bromomethyl)-5-phenylpenta-2,4-dienoate 2k (222.8 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded the title compound 3ak.

Yield: 97.8 mg (57%); colorless solid; mp 143–145 °C; R_f = 0.35 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>95:5) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.89–7.86 (m, 2 H), 7.62 (dd, J = 7.3, 3.5 Hz, 1 H), 7.56–7.47 (m, 3 H), 7.44 (dd, J = 8.0, 1.6 Hz, 2 H), 7.36 (m, 3 H), 6.96–6.93 (m, 2 H), 4.43 (s, 2 H), 3.53 (s, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.5, 145.8, 143.8, 138.7, 135.8, 134.0, 129.8, 129.1 (2C), 129.0 (2C), 128.9 (2C), 127.9 (2C), 123.0, 118.1, 54.7, 52.3.

The title compound is known in the literature and the data are consistent with reported values.[10a] [d]

Methyl (Z)-5-Phenyl-2-[(phenylsulfonyl)methyl]pent-2-enoate (3al)

Obtained by following G1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-5-phenylpent-2-enoate 2l (212.3 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded the title compound 3al.

Yield: 161.7 mg (94%); colorless liquid; R_f = 0.41 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>92:8) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.95 (dd, J = 8.3, 1.2 Hz, 2 H), 7.73 (tt, J = 7.4, 1.2 Hz, 1 H), 7.63 (t, J = 7.7 Hz, 2 H), 7.43–7.38 (m, 2 H), 7.32 (d, J = 7.4 Hz, 1 H), 7.30 –7.27 (m, 3 H), 4.27 (s, 2 H), 3.57 (s, 3 H), 2.87 (t, J = 7.6 Hz, 2 H), 2.66 (q, J = 7.6 Hz, 2 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.0, 150.5, 140.5, 138.9, 133.9, 129.1 (2C), 128.8 (2C), 128.6 (2C), 128.5 (2C), 126.4, 121.2, 54.1, 52.2, 34.3, 31.5.

LCMS (ESI): m/z 344.95 [M]⁺.

Methyl (Z)-5-Methyl-2-[(phenylsulfonyl)methyl]hex-2-enoate (3am)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125.0 mg, 0.5 mmol), methyl (Z)-2-(bromomethyl)-5-methylhex-2-enoate 2m (165.8 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 10% EtOAc in petroleum ether) yielded the title compound 3am.

Yield: 134.9 mg (91%); colorless liquid; R_f = 0.30 (20% EtOAc in petroleum ether); mixture of Z/E isomers (80:20) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.83 (dd, J = 8.4, 1.2 Hz, 2 H), 7.62 (tt, J = 7.4, 1.2 Hz, 1 H), 7.51 (t, J = 7.7 Hz, 2 H), 7.14 (t, J = 7.5 Hz, 1 H), 4.22 (s, 2 H), 3.46 (s, 3 H), 2.08 (t, J = 7.2 Hz, 2 H), 1.77–1.67 (m, 1 H), 0.89 (d, J = 6.7 Hz, 6 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.2, 151.1, 133.9, 129.6, 129.1 (2C), 128.9 (2C), 121.2, 54.3, 52.2, 38.4, 28.2, 22.5 (2C).

LCMS (ESI): m/z 296.95 [M]⁺.

Ethyl (Z)-3-Phenyl-2-[(phenylsulfonyl)methyl]acrylate (3an)

Obtained by following GP1 using S-phenyl benzenesulfonothioate 1a (125 mg, 0.5 mmol), ethyl (Z)-2-(bromomethyl)-3-phenylacrylate 2n (201.8 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded the title compound 3an.

Yield: 158.7 mg (96%); colorless liquid; R_f = 0.40 (20% EtOAc/hexanes); mixture of Z/E isomers (>98:2) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 7.93 (s, 1 H), 7.84 (dd, J = 8.4, 1.2 Hz, 2 H), 7.58 (tt, J = 7.4, 1.2 Hz, 1 H), 7.49–7.44 (m, 4 H), 7.37–7.33 (m, 3 H), 4.49 (s, 2 H), 4.03 (q, J = 7.1 Hz, 2 H), 1.22 (t, J = 7.1 Hz, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.6, 146.2, 139.5, 133.85, 133.81, 129.7, 129.3 (2C), 129.1 (2C), 128.9 (2C), 128.6 (2C), 121.3, 61.7, 55.2, 14.2.

The title compound is known in the literature and the data are consistent with reported values.[9d]

Ethyl (Z)-3-Phenyl-2-(tosylmethyl)acrylate (3bn)

Obtained by following GP1 using S-(p-tolyl) 4-methylbenzenesulfonothioate 1b (139.1 mg, 0.5 mmol), ethyl (Z)-2-(bromomethyl)-3-phenylacrylate 2n (191.3 mg, 0.75 mmol), and Cs₂CO₃ (162.5 mg, 0.5 mmol) for 4 h. Purification by flash column chromatography (silica gel, 15% EtOAc in petroleum ether) yielded the title compound 3bn.

Yield: 168.7 mg (98%); colorless liquid; R_f = 0.42 (20% EtOAc in petroleum ether); mixture of Z/E isomers (>98:2) based on ¹H NMR analysis.

¹H NMR (400 MHz, CDCl₃): δ = 8.01 (s, 1 H), 7.80 (d, J = 8.2 Hz, 2 H), 7.56 (dd, J = 6.5, 2.7 Hz, 2 H), 7.47–7.44 (m, 3 H), 7.35 (d, J = 8.2 Hz, 2 H), 4.58 (s, 2 H), 4.16 (q, J = 7.1 Hz, 2 H), 2.51 (s, 3 H), 1.34 (t, J = 7.1 Hz, 3 H).

¹³C NMR (101 MHz, CDCl₃): δ = 166.6, 146.0, 144.8, 136.5, 133.9, 129.74 (2C), 129.68, 129.3 (2C), 128.8 (2C), 128.7 (2C), 121.5, 61.7, 55.2, 21.7, 14.2.

The title compound is known in the literature and the data are consistent with reported values.[10d]

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• 12c Reddy RJ, Waheed M, Kumar JJ. RSC Adv. 2018; 8: 40446
• 12d Reddy RJ, Waheed M, Karthik T, Shankar A. New J. Chem. 2018; 42: 980
• 12e Reddy RJ, Kumari AH. RSC Adv. 2021; 11: 9130
• 12f Reddy RJ, Kumari AH, Kumar J. J. Org. Biomol. Chem. 2021;

For reviews of thiyl radicals in organic synthesis, see:
• 13a Subramanian H, Moorthy R, Sibi MP. Angew. Chem. Int. Ed. 2014; 53: 13660
• 13b Dénès F, Pichowicz M, Povie G, Renaud P. Chem. Rev. 2014; 114: 2587

The mixture of Z/E isomers of allyl sulfones was based on the corresponding MBH allyl bromides, see:
• 14a Basavaiah D, Reddy KR, Kumaragurubaran N. Nat. Protoc. 2007; 2: 2665
• 14b Basavaiah D. J. Sci. Res. Banaras Hindu Univ. 2019; 63: 169

In the ¹H NMR spectra of aryl substituted products, the vinylic proton cis- to the ester group appears around δ = 7.90 ppm and around δ = 6.85 ppm for the Z- and E-isomers, respectively. Similarly, the vinylic proton of the major Z-isomer appears at around δ = 7.09 ppm and a minor peak for the E-isomer appears at around δ = 6.08 ppm for alkyl substituted products. See:
• 15a Basavaiah D, Muthukumaran K, Sreenivasulu B. Synthesis 2000; 545
• 15b Manson PH, Esmile ND. Tetrahedron 1994; 41: 12001
• 15c Shanmugam P, Singh PR. Synlett 2001; 1314 ; see also ref. 9a
• 16a Poshkus AC, Herweh JE, Magnotta FA. J. Org. Chem. 1963; 28: 2766
• 16b Kirihara M, Naito S, Nishimura Y, Ishizuka Y, Iwai T, Takeuchi H, Ogata T, Hanai H, Kinoshita Y, Kishida M, Yamazaki K, Noguchi T, Yamashoji S. Tetrahedron 2014; 70: 2464
• 16c Silva-Cuevas C, Perez-Arrieta C, Polindara-García LA, Lujan-Montelongo JA. Tetrahedron Lett. 2017; 58: 2244