Stereoselective C-C Bond-Forming Reaction of α-Ethynyl Ketene-S,S-acetals with Aldehydes in the Presence of Titanium Tetrahalides

Yu-Long Zhao; Li Chen; Qun Liu; Dong-Wei Li

doi:10.1055/s-2006-956489

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Synlett 2007(1): 0037-0042
DOI: 10.1055/s-2006-956489

LETTER

Stereoselective C-C Bond-Forming Reaction of α-Ethynyl Ketene-S,S-acetals with Aldehydes in the Presence of Titanium Tetrahalides

Yu-Long Zhao*, Li Chen, Qun Liu*, Dong-Wei Li
Department of Chemistry, Northeast Normal University, Changchun 130024, P. R. of China
e-Mail: zhaoyl351@nenu.edu.cn;

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Publication History

Received 30 June 2006
Publication Date:
20 December 2006 (online)

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Abstract

A highly stereoselective C-C bond-forming reaction was achieved. In the presence of titanium tetrahalides, reaction of conjugated enynes, α-ethynyl-α′-methoxycarbonyl ketene-S,S-acetals, with aldehydes gave (E,Z)-3,7-dihalo-3,6-dienedioates in good to high yields. A mechanism for the C-C bond-forming reaction is detailed and considered to be a concerted process.

Key words

alkynes - aldehydes - titanium tetrahalides - coupling reaction - stereoselectivity

References and Notes

1a Current Trends in Organic Synthesis Scolastico C. Nocotra F. Plenum; New York: 1999.

Google Scholar
For recent reviews, see:
1b Li C.-J. Chem. Rev. 2005, 105: 3095

Google Scholar
1c Dilman AD. Ioffe SL. Chem. Rev. 2003, 103: 733

Google Scholar
1d Fagnou K. Lautens M. Chem. Rev. 2003, 103: 169

Google Scholar
1e For a review on olefin metathesis, see: Diver ST. Giessert AJ. Chem. Rev. 2004, 104: 1317

Google Scholar
For a microreview on the reactions of 1,4-dilithio-1,3-dienes with carbonyl compounds, see:
2a Xi Z. Eur. J. Org. Chem. 2004, 2773

Crossref Google Scholar
For selected examples, see:
2b Xi Z. Song Q. Chen J. Guan H. Li P. Angew. Chem. Int. Ed. 2001, 40: 1913

Crossref Google Scholar
2c Song Q. Chen J. Jin X. Xi Z. J. Am. Chem. Soc. 2001, 123: 10419

Crossref Google Scholar
3 For an example of the synthesis of dipyrromethane from α-alkylthiopyrrole and benzaldehyde, see: Thamyongkit P. Bhise AD. Taniguchi M. Lindsey JS. J. Org. Chem. 2006, 71: 903

Crossref Google Scholar
4 Okauchi T. Tanaka T. Minami T. J. Org. Chem. 2001, 66: 3924

Crossref Google Scholar
5 Yin Y.-B. Wang M. Liu Q. Hu J.-L. Sun S.-G. Kang J. Tetrahedron Lett. 2005, 46: 4399

Crossref Google Scholar
6a Kabalka GW. Wu Z. Ju Y. Org. Lett. 2002, 4: 1491

Crossref Google Scholar
6b Kabalka GW. Wu Z. Ju Y. Org. Lett. 2002, 4: 3415

Crossref Google Scholar
6c Yadav JS. Reddy BVS. Eeshwaraiah B. Gupta MK. Biswas SK. Tetrahedron Lett. 2005, 46: 1161

Crossref Google Scholar
7 Miranda PO. Diaz DD. Padron JI. Ramirez MA. Martin VS. J. Org. Chem. 2005, 70: 57

Crossref Google Scholar
8a Saito S. Salter MM. Gevorgyan V. Tsuboya N. Tando K. Yamamoto Y. J. Am. Chem. Soc. 1996, 118: 3970

Crossref Google Scholar
8b Gevorgyan V. Takeda A. Homma M. Sadayori N. Radhakrishnan U. Yamamoto Y. J. Am. Chem. Soc. 1999, 121: 6391

Crossref Google Scholar
8c Saito S. Chounan Y. Nogami T. Fukushi T. Tsuboya N. Yamada Y. Kitahara H. Yamamoto Y. J. Org. Chem. 2000, 65: 5350

Crossref Google Scholar
9a Hansen EC. Lee D. Org. Lett. 2004, 6: 2035

Crossref Google Scholar
9b Kang B. Kim D.-H. Do Y. Chang S. Org. Lett. 2003, 5: 3041

Crossref Google Scholar
10 Hayes ME. Shinokubo H. Danheiser RL. Org. Lett. 2005, 7: 3917

Crossref PubMed Google Scholar
11a Saito S. Tanaka T. Koizumi T. Tsuboya N. Itagaki H. Kawasaki T. Endo S. Yamamoto Y. J. Am. Chem. Soc. 2000, 122: 1810

Crossref Google Scholar
11b Treitel N. Eshdat L. Sheradsky T. Donovan PM. Tykwinski RR. Scott LT. Hopf H. Rabinovitz M. J. Am. Chem. Soc. 2006, 128: 4703

Crossref Google Scholar
Reviews:
12a Dieter RK. Tetrahedron 1986, 42: 3029

Article in Thieme Connect Google Scholar
12b Junjappa H. Tla H. Asokan CV. Tetrahedron 1990, 46: 5423

Article in Thieme Connect Google Scholar
12c Tla H. Junjappa H. Barun O. J. Organomet. Chem. 2001, 624: 34

Article in Thieme Connect Google Scholar
12d Elgemeie GH. Sayed SH. Synthesis 2001, 1747

Article in Thieme Connect Google Scholar
For selected examples, see:
13a Bi X. Dong D. Liu Q. Pan W. Zhao L. Li B. J. Am. Chem. Soc. 2005, 127: 4578

Crossref PubMed Google Scholar
13b Kang J. Liang F. Sun S.-G. Liu Q. Bi X.-H. Org. Lett. 2006, 8: 2547

Crossref PubMed Google Scholar
13c Ouyang Y. Dong D. Yu H. Liang Y. Liu Q. Adv. Synth. Catal. 2006, 348: 206

Crossref PubMed Google Scholar
13d Zhao L. Liang F. Bi X. Sun S. Liu Q. J. Org. Chem. 2006, 71: 1094

Crossref PubMed Google Scholar
13e Dong DW. Bi X. Liu Q. Cong FD. Chem. Commun. 2005, 28: 3580

Crossref PubMed Google Scholar
13f Bi X. Dong D. Li Y. Liu Q. J. Org. Chem. 2005, 70: 10886

Crossref PubMed Google Scholar
14 Dong D. Liu Y. Zhao Y.-L. Qi Y. Wang Z. Liu Q. Synthesis 2005, 85

Article in Thieme Connect Google Scholar
15a Zhao Y.-L. Liu Q. Zhang J.-P. Liu Z.-Q. J. Org. Chem. 2005, 70: 6913

Crossref Google Scholar
15b Zhao Y.-L. Zhang W. Zhang J.-Q. Liu Q. Tetrahedron Lett. 2006, 47: 3157

Crossref Google Scholar
16 Zhao Y.-L. Liu Q. Zhang Y.-F. Sun S.-G. Li Y.-N. Synlett 2006, 231

Article in Thieme Connect Google Scholar
19 Yahiro S. Shibata K. Saito T. Okauchi T. Minami T. J. Org. Chem. 2003, 68: 4947

Crossref Google Scholar
20a Liu Q. Che G. Yu H. Liu Y. Zhang J. Zhang Q. Dong DW. J. Org. Chem. 2003, 68: 9148

Crossref Google Scholar
20b Dong D. Ouyang Y. Yu H. Liu Q. Liu J. Wang M. Zhu J. J. Org. Chem. 2005, 70: 4535

Crossref Google Scholar
22a Koskinen AMP. Karisalmi K. Chem. Soc. Rev. 2005, 34: 677

Crossref Google Scholar
22b Staunton J. Wilkinson B. Chem. Rev. 1997, 97: 2611

Crossref Google Scholar
23a Kabalka GW. Yao M.-L. Borella S. Wu Z.-Z. Org. Lett. 2005, 7: 2865

Crossref Google Scholar
23b Kabalka GW. Wu Z. Ju Y. Yao M.-L. J. Org. Chem. 2005, 70: 10285

Crossref Google Scholar
23c Kabalka GW. Yao M.-L. Borella S. Wu Z. Chem. Commun. 2005, 2492

Crossref Google Scholar

17

Preparation of Compounds 3 (3ae as example); Typical Procedure: To a stirred solution of enyne 1a (2.0 mmol, 428 mg) and 4-nitrobenzaldehyde (2e; 1.0 mmol, 151 mg) in anhyd CH₂Cl₂ (20 mL) cooled to 0 °C in an ice bath, TiCl₄ (1.0 mmol, 0.11 mL) was added dropwise by syringe within 3 min under a nitrogen atmosphere. Then the reaction mixture was stirred for 1 h at 0 °C. After 1a was consumed (monitored by TLC), the reaction mixture was poured into a sat. NaHCO₃ solution (50 mL) and extracted with CH₂Cl₂ (2 × 10 mL). The combined organic extracts were dried over anhyd MgSO₄, filtered and concentrated under reduced pressure to yield the corresponding crude product, which was purified by silica gel chromatography (Et₂O-hexane = 1:1) to give 3ae (444 mg, 70%) as a white crystal.
(3 Z ,6 E )-Dimethyl 3,7-Dichloro-2,8-di(1,3-dithian-2-ylidene)-5-(4-nitrophenyl)nona-3,6-dienedioate ( 3ae): white crystalline solid; mp 184-186 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.15-2.20 (m, 4 H), 2.92-2.96 (m, 8 H), 3.60 (br s, 3 H), 3.75 (s, 3 H), 4.70 (t, J = 9.5 Hz, 1 H), 5.70 (d, J = 9.5 Hz, 1 H), 6.00 (d, J = 9.5 Hz, 1 H), 7.50 (d, J = 8.5 Hz, 2 H), 8.15 (q, J = 8.5 Hz, 2 H). ¹³C NMR (125 MHz, CDCl₃): δ = 23.48 (2 × C), 29.38 (2 × C), 29.51, 29.92, 45.63 (2 × C), 52.20, 123.33 (2 × C), 123.81 (2 × C), 128.91 (2 × C), 131.75, 132.57, 146.98 (2 × C), 163.98 (2 × C), 164.23 (2 × C), 164.66 (2 × C). IR (KBr): 1009, 1193, 1253, 1346, 1493, 1518, 1694, 2946, 3445 cm^-1. MS (EI): m/z = 657 [M + 23]⁺. Anal. Calcd for C₂₅H₂₅Cl₂NO₆S₄: C, 47.31; H, 3.97; N, 2.21. Found: C, 47.50; H, 3.82; N, 2.03.
(3 Z ,6 E )-Dimethyl 3,7-Dichloro-2,8-di(1,3-dithian-2-ylidene)-5-phenylnona-3,6-dienedioate ( 3aa): white crystalline solid; mp 168-170 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.13-2.19 (m, 4 H), 2.89-3.00 (m, 8 H), 3.58 (br s, 3 H), 3.72 (s, 3 H), 4.62 (t, J = 9.5 Hz, 1 H), 5.73 (d, J = 9.0 Hz, 1 H), 6.11 (d, J = 9.0 Hz, 1 H), 7.19-7.22 (m, 1 H), 7.28-7.31 (m, 4 H). ¹³C NMR (125 MHz, CDCl₃): δ = 23.20 (2 × C), 29.04 (2 × C), 29.16, 29.52, 45.43 (2 × C), 51.77, 123.51 (2 × C), 126.62 (2 × C), 127.63 (2 × C), 128.24 (2 × C), 132.91, 133.80, 163.70 (2 × C), 163.73 (2 × C), 164.17 (2 × C). IR (KBr): 742, 859, 1007, 1145, 1256, 1494, 1692, 2943, 3443 cm^-1. MS (EI): m/z = 589 [M + 1]⁺. Anal. Calcd for C₂₅H₂₆Cl₂O₄S₄: C, 50.92; H, 4.44. Found: C, 51.11;
H, 4.60.
(3 Z ,6 E )-Dimethyl 5-(Benzo[ d ][1,3]dioxol-5-yl)-3,7-dichloro-2,8-di(1,3-dithian-2-ylidene)nona-3,6-dienedioate ( 3ab): white crystalline solid; mp 172-174 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.16-2.19 (m, 4 H), 2.94-2.95 (m, 8 H), 3.68 (br s, 3 H), 3.75 (s, 3 H), 4.53 (t, J = 9.5 Hz, 1 H), 5.68 (d, J = 9.0 Hz, 1 H), 5.92 (s, 2 H), 6.03 (d, J = 9.5 Hz, 1 H), 6.72 (d, J = 8.5 Hz, 1 H), 6.77 (d, J = 8.5 Hz, 1 H), 6.86 (s, 1 H). ¹³C NMR (125 MHz, CDCl₃): δ = 23.07, 23.19, 29.03, 29.16, 29.37, 29.52, 44.95, 51.53, 51.76, 100.84, 107.89, 108.10, 108.17, 108.27, 120.32, 120.54, 123.38, 128.21, 128.85, 132.98, 133.31, 133.64, 145.93, 147.56, 163.75, 164.08. IR (KBr): 2924, 2853, 1695, 1506, 1457, 1436, 1252 cm^-1. MS (EI): m/z = 655 [M + 23]⁺. Anal. Calcd for C₂₆H₂₆Cl₂O₆S₄: C, 49.28; H, 4.14. Found: C, 49.38; H, 4.23.
(3 Z ,6 E )-Dimethyl 3,7-Dichloro-2,8-di(1,3-dithian-2-ylidene)-5-(4-methoxyphenyl)nona-3,6-dienedioate ( 3ac): white crystalline solid; mp 170-172 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.13-2.19 (m, 4 H), 2.92-2.95 (m, 8 H), 3.62-3.74 (br s, 3 H), 3.74 (s, 3 H), 3.77 (s, 3 H), 4.56 (t, J = 9.0 Hz, 1 H), 5.70 (d, J = 9.0 Hz, 1 H), 6.07 (d, J = 9.0 Hz, 1 H), 6.82 (d, J = 8.5 Hz, 2 H), 7.23 (d, J = 8.5 Hz, 2 H). ¹³C NMR (125 MHz, CDCl₃): δ = 23.54 (2 × C), 29.37 (2 × C), 29.50, 29.86, 44.95, 52.11 (2 × C), 55.51, 113.90 (2 × C), 123.90 (2 × C), 128.95 (2 × C), 133.53, 134.35, 158.53 (2 × C), 163.97 (2 × C), 164.12 (2 × C), 164.52 (2 × C). IR (KBr): 1010, 1193, 1255, 1464, 1508, 1644, 1691, 2925, 3443 cm^-1. MS (EI): m/z = 641 [M + 23]⁺. Anal. Calcd for C₂₆H₂₈Cl₂O₅S₄: C, 50.39; H, 4.55. Found: C, 50.18; H, 4.51.
(3 Z ,6 E )-Dimethyl 3,7-Dichloro-2,8-di(1,3-dithian-2-ylidene)-5-(p -tolyl)nona-3,6-dienedioate ( 3ad): white crystalline solid; mp 178-180 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.15-2.20 (m, 4 H), 2.31 (s, 3 H), 2.92-2.97 (m, 8 H), 3.62 (br s, 3 H), 3.75 (s, 3 H), 4.58 (t, J = 9.0 Hz, 1 H), 5.72 (d, J = 8.5 Hz, 1 H), 6.08 (d, J = 9.0 Hz, 1 H), 7.09 (d, J = 8.0 Hz, 2 H), 7.16 (d, J = 8.0 Hz, 2 H). ¹³C NMR (125 MHz, CDCl₃): δ = 20.99, 23.23, 29.06, 29.17, 29.35, 29.54, 30.91, 45.08 (2 × C), 51.77, 123.60, 127.36, 127.51, 128.68, 128.96, 129.13, 133.20, 133.52, 133.95, 136.15, 163.58 (2 × C), 163.79 (2 × C), 164.21 (2 × C). IR (KBr): 1008, 1190, 1251, 1505, 1692, 2856, 2923, 3442 cm^-1. MS (EI): m/z = 603 [M + 1]⁺. Anal. Calcd for C₂₆H₂₈Cl₂O₄S₄: C, 51.73; H, 4.68. Found: C, 51.90; H, 4.80.
(3 Z ,6 E )-Dimethyl 3,7-Dichloro-2,8-di(1,3-dithian-2-ylidene)-5-(thiophen-2-yl)nona-3,6-dienedioate ( 3af): white crystalline solid; mp 179-180 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.15-2.20 (m, 4 H), 2.93-2.99 (m, 8 H), 3.72 (br s, 3 H), 3.75 (s, 3 H), 4.80 (t, J = 9.0 Hz, 1 H), 5.73 (d, J = 8.0 Hz, 1 H), 6.06 (d, J = 9.5 Hz, 1 H), 6.94 (q, J = 6.0 Hz, 2 H), 7.18 (d, J = 6.0 Hz, 1 H). ¹³C NMR (125 MHz, CDCl₃): δ = 23.21 (2 × C), 29.05, 29.19, 29.45, 30.90, 41.46 (2 × C), 51.77, 123.30 (2 × C), 124.41 (2 × C), 124.58, 126.63, 132.31, 132.82, 163.72 (2 × C), 163.90 (2 × C), 164.13 (2 × C). IR (KBr): 853, 1008, 1194, 1254, 1433, 1493, 1692, 2945 cm^-1. MS (EI): m/z = 617 [M + 23]⁺.
(3 Z ,6 E )-Dimethyl 3,7-Dichloro-5-(4-chlorophenyl)-2,8-di(1,3-dithian-2-ylidene)nona-3,6-dienedioate ( 3ag): white crystalline solid; mp 142-144 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.15-2.20 (m, 4 H), 2.93-2.95 (m, 8 H), 3.60 (br s, 3 H), 3.75 (s, 3 H), 4.58 (t, J = 9.5 Hz, 1 H), 5.69 (d, J = 9.0 Hz, 1 H), 6.06 (d, J = 9.0 Hz, 1 H), 7.27 (m, 4 H). ¹³C NMR (125 MHz, CDCl₃): δ = 23.20 (2 × C), 29.06 (2 × C), 29.19, 29.56, 44.84 (2 × C), 51.81, 123.34 (2 × C), 128.35 (2 × C), 128.53 (2 × C), 129.05, 132.43, 133.34 (2 × C), 163.66 (2 × C), 163.92 (2 × C), 164.08 (2 × C). IR (KBr): 1011, 1195, 1258, 1460, 1258, 1496, 1693, 2861, 2926, 3441 cm^-1. MS (EI): m/z = 645 [M + 23]⁺.
(3 Z ,6 E )-Dimethyl 3,7-Dichloro-2,8-di(1,3-dithian-2-ylidene)-5-(4-fluorophenyl)nona-3,6-dienedioate ( 3ah): white crystalline solid; mp 144-146 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.15-2.16 (m, 4 H), 2.78-2.92 (m, 8 H), 3.61 (br s, 3 H), 3.73 (s, 3 H), 4.58 (t, J = 9.5 Hz, 1 H), 5.68 (d, J = 9.0 Hz, 1 H), 6.06 (d, J = 9.0 Hz, 1 H), 6.96 (t, J = 8.5 Hz, 2 H), 7.26 (d, J = 8.5 Hz, 2 H). ¹³C NMR (125 MHz, CDCl₃): δ = 23.21 (2 × C), 29.06, 29.18, 29.39, 29.55, 44.71 (2 × C), 51.78, 114.94, 115.11, 123.42 (2 × C), 129.13 (2 × C), 129.19 (2 × C), 132.67, 133.64, 160.63 (2 × C), 162.58, 163.67, 163.74, 164.09. IR (KBr): 2949, 1689, 1508, 1487, 1250, 1219, 1158, 916 cm^-1. MS (EI): m/z = 607 [M + 1]⁺.
(3 Z ,6 E )-Dimethyl 3,7-Dichloro-2,8-di(1,3-dithian-2-ylidene)-5-[( E )-styryl]nona-3,6-dienedioate ( 3ai): white solid; mp 220-222 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.16-2.19 (m, 4 H), 2.95-2.96 (m, 8 H), 3.72 (br s, 3 H), 3.75 (s, 3 H), 4.18 (q, J = 8.5 Hz, 1 H), 5.60 (d, J = 9.0 Hz, 1 H), 5.93 (d, J = 9.0 Hz, 1 H), 6.08 (d, J = 10 Hz, 1 H), 6.49 (d, J = 10 Hz, 1 H), 7.20-7.23 (m, 1 H), 7.28-7.33 (m, 4 H). ¹³C NMR (125 MHz, CDCl₃): δ = 23.25 (2 × C), 29.13, 29.38, 29.58, 30.88, 43.64 (2 × C), 51.78, 109.69, 123.61, 126.17 (2 × C), 127.31 (2 × C), 127.74, 128.44 (2 × C), 130.66, 132.64 (2 × C), 137.18 (2 × C), 163.78 (2 × C), 164.14 (2 × C). IR (KBr): 876, 1009, 1196, 1255, 1452, 1692, 2990, 3444 cm^-1. MS (EI): m/z = 615 [M + 1]⁺. Anal. Calcd for C₂₇H₂₈Cl₂O₄S₄: C, 52.67; H, 4.58. Found: C, 52.93; H, 4.80.
(3 Z ,6 E )-Dimethyl 5-(Benzo[d][1,3]dioxol-5-yl)-3,7-dibromo-2,8-di(1,3-dithian-2-ylidene)nona-3,6-dienedioate ( 3aj): white crystalline solid; mp 178-180 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.19-2.23 (m, 4 H), 2.96-3.05 (m, 8 H), 3.68 (br s, 3 H), 3.78 (s, 3 H), 4.48 (t, J = 9.5 Hz, 1 H), 5.83 (d, J = 9.0 Hz, 1 H), 5.91 (s, 2 H), 6.27 (q, J = 9.0 Hz, 1 H), 6.74 (d, J = 8.0 Hz, 1 H), 6.79 (d, J = 8.0 Hz, 1 H), 6.89 (s, 1 H). ¹³C NMR (125 MHz, CDCl₃): δ = 23.31, 23.55, 29.30, 29.35, 29.59, 29.85, 48.75, 49.06, 52.04, 101.14, 108.22, 108.44, 108.58, 108.67, 120.74, 120.95, 121.06, 125.27, 133.51, 133.92, 136.25, 136.42, 146.54, 148.03, 163.54, 164.41. IR (KBr): 1184, 1209, 1413, 1560, 1607, 1687, 2987 cm^-1. MS (EI): m/z = 721 [M + 1]⁺.
(3 Z ,6 E )-Dimethyl 5-(Benzo[d][1,3]dioxol-5-yl)-3,7-dichloro-2,8-di(1,3-dithiolan-2-ylidene)nona-3,6-dienedioate ( 3bb): white crystalline solid; mp 192-194 °C. ¹H NMR (500 MHz, CDCl₃): δ = 3.34-3.49 (m, 8 H), 3.71 (br s, 3 H), 3.77 (s, 3 H), 4.60 (t, J = 9.5 Hz, 1 H), 5.76 (d, J = 9.0 Hz, 1 H), 5.95 (s, 2 H), 6.07 (d, J = 9.0 Hz, 1 H), 6.74 (q, J = 8.0 Hz, 2 H), 6.90 (s, 1 H). ¹³C NMR (125 MHz, CDCl₃): δ = 37.10 (2 × C), 39.86 (2 × C), 45.09 (2 × C), 52.29, 101.19, 108.28, 108.51, 111.72, 115.55, 120.73, 130.11, 130.61, 133.02, 133.91, 146.53, 147.96, 165.00, 165.33 (2 × C), 168.41, 170.13. IR (KBr): 934, 1040, 1194, 1249, 1433, 1507, 1685, 2947, 3649 cm^-1. MS (EI): m/z = 605 [M + 1]⁺. Anal. Calcd for C₂₄H₂₂Cl₂O₆S₄: C, 47.60; H, 3.66. Found: C, 47.76; H, 3.79.
(3 Z ,6 E )-Dimethyl 3,7-Dichloro-2,8-di(1,3-dithiolan-2-ylidene)-5-(4-nitrophenyl)nona-3,6-dienedioate ( 3be): white crystalline solid; mp 213-215 °C. ¹H NMR (500 MHz, CDCl₃): δ = 3.36-3.66 (m, 8 H), 3.66 (br s, 3 H), 3.77 (s, 3 H), 4.74 (t, J = 9.5 Hz, 1 H), 5.80 (d, J = 9.5 Hz, 1 H), 6.05 (d, J = 9.5 Hz, 1 H), 7.48 (d, J = 8.5 Hz, 2 H), 8.16 (d, J = 8.5 Hz, 2 H). ¹³C NMR (125 MHz, CDCl₃): δ = 36.79, 36.92, 39.66 (2 × C), 45.22 (2 × C), 52.13, 114.86 (2 × C), 123.62 (2 × C), 128.52 (2 × C), 131.00, 131.43, 146.79 (2 × C), 164.49 (2 × C), 164.83 (2 × C), 168.58 (2 × C). IR (KBr): 1013, 1196, 1248, 1266, 1347, 1435, 1516, 1685, 2948, 3446 cm^-1. MS (EI): m/z = 628 [M + 23]⁺.

18

Crystal data for 3ae: C₂₅H₂₅Cl₂NO₆S₄; white crystal, M = 634.60, monoclinic, P2₁/n, a = 11.241 (7) Å, b = 13.167 (8) Å, c = 19.679 (9) Å, α = 90.00°, β = 95.203(12)°, γ = 90.00°, V = 2901 (3) Å³, Z = 4, T = 293 (2) K, F₀₀₀ = 1312, R ₁ = 0.0739, wR ₂ = 0.1462. The CCDC deposition number is 293614.

21

Synthesis of Compounds 4 (4ab as example); Typical Procedure: To a stirred solution of compound 3ab (1.0 mmol, 633 mg) in EtOH (15 mL) was added HCl (0.5 mmol, 0.043 mL) in one portion. Then the reaction mixture was heated to the reflux temperature for 1 h. After 3ab was consumed (monitored by TLC), the reaction mixture was poured into H₂O (50 mL) and extracted with Et₂O (3 × 10 mL). The combined organic extracts were dried over anhyd MgSO₄, filtered and concentrated under reduced pressure to yield the corresponding crude product, which was purified by chromatography over silica gel column using Et₂O-hexane (1:2) as eluent to give 4ab (417 mg, 70%) as a white crystal.
Dimethyl 5-(Benzo[d][1,3]dioxol-5-yl)-2,8-di(1,3-dithian-2-ylidene)-3,7-dioxononanedioate ( 4ab): white crystalline solid; mp 124-126 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.16-2.22 (m, 4 H), 2.76-2.79 (m, 4 H), 2.80 (d, J = 8.0 Hz, 1 H), 2.83 (d, J = 8.0 Hz, 1 H), 2.89-2.92 (m, 4 H), 2.93 (d, J = 6.5 Hz, 1 H), 2.96 (d, J = 6.5 Hz, 1 H), 3.68 (dd, J = 6.5, 8.0 Hz, 1 H), 3.80 (s, 6 H), 5.88 (s, 2 H), 6.64-6.67 (m, 3 H). ¹³C NMR (125 MHz, CDCl₃): δ = 23.85 (2 × C), 29.16 (2 × C), 29.35 (2 × C), 37.24 (2 × C), 47.95, 52.04 (2 × C), 100.66, 107.94, 108.06, 120.68, 127.52, 137.34, 145.80, 147.25 (2 × C), 165.21 (2 × C), 169.53 (2 × C), 195.17 (2 × C). IR (KBr): 932, 1039, 1247, 1457, 1488, 1506, 1653, 1698, 3446 cm^-1. MS (EI): m/z = 597 [M + 1]⁺. Anal. Calcd for C₂₆H₂₈O₈S₄: C, 52.33; H, 4.73. Found: C, 52.51; H, 4.88.
Dimethyl 2,8-Di(1,3-dithian-2-ylidene)-3,7-dioxo-5- para -tolylnonanedioate ( 4ad): white crystalline solid; mp 119-121 °C. ¹H NMR (500 MHz, CDCl₃): δ = 2.16-2.21 (m, 4 H), 2.27 (s, 3 H), 2.74-2.77 (m, 4 H), 2.80 (d, J = 7.0 Hz, 1 H), 2.84 (d, J = 7.0 Hz, 1 H), 2.85-2.91 (m, 4 H), 2.97 (d, J = 7.0 Hz, 1 H), 2.99 (d, J = 7.0 Hz, 1 H), 3.71 (t, J = 7.0 Hz, 1 H), 3.79 (s, 6 H), 7.03 (d, J = 8.0 Hz, 2 H), 7.06 (d, J = 8.0 Hz, 2 H). ¹³C NMR (125 MHz, CDCl₃): δ = 21.27 (2 × C), 24.16, 29.30 (4 × C), 37.35 (2 × C), 48.24, 52.33 (2 × C), 120.77, 127.85, 129.14 (2 × C), 129.28, 135.92, 140.69 (2 × C), 165.48 (2 × C), 169.53 (2 × C), 195.79
(2 × C).
IR (KBr): 816, 1074, 1247, 1439, 1469, 1659, 1697, 2946 cm^-1. MS (EI): m/z = 567 [M + 1]⁺.