Dichotomous Reaction Pathways for the Oxidative Palladium(II)-Catalyzed Intramolecular Acyloxylation of Alkenes

Abstract

This work provides an in-depth investigation of the Pd(II)-catalyzed oxidative cyclization of various alkenoic acids bearing different tethers between the carboxylic acid moiety and the olefin function, showcasing how different mechanistic pathways (oxypalladation or allylic C–H activation) can be operative. The factors biasing toward one or the other of these reactivities are rationally discussed and compared with our recent studies on the Pd(II)-catalyzed intramolecular amination.

Key words

palladium(II) - C–H activation - oxypalladation - reaction mechanisms - alkenoic acids

• References and Notes

• 1 On leave from UR-CHEMS, Université Constantine 1, 25000 Constantine, Algeria.

For books on this topic, see:
• 2a Bäckvall J.-E In Modern Oxidation Methods . Wiley-VCH; Weinheim: 2004
• 2b Tsuji J In Palladium Reagents and Catalysts . Wiley; New York: 2004. 2nd ed.
• 2c Negishi E.-I In Handbook of Organopalladium Chemistry for Organic Synthesis . John Wiley & Sons, Inc; New York: 2002

For recent reviews on nucleopalladation, see:
• 3a Kočovský P, Bäckvall J.-E. Chem. Eur. J. 2015; 21: 36
• 3b McDonald RI, Liu G, Stahl SS. Chem. Rev. 2011; 111: 2981
• 3c Keith JA, Henry PM. Angew. Chem. Int. Ed. 2009; 48: 9038
• 3d Minatti A, Muñiz K. Chem. Soc. Rev. 2007; 36: 1142
• 3e Beccalli EM, Broggini G, Martinelli M, Sottocornola S. Chem. Rev. 2007; 107: 5318

For recent reviews on allylic C–H activation, see:
• 4a Liron F, Oble J, Lorion MM, Poli G. Eur. J. Org. Chem. 2014; 20: 5863
• 4b Breder A. Synlett 2014; 25: 899
• 4c Ramirez TA, Zhao B, Shi Y. Chem. Soc. Rev. 2012; 41: 931
• 4d Engelin CJ, Fristrup P. Molecules 2011; 16: 951
• 4e Jensen T, Fristrup P. Chem. Eur. J. 2009; 15: 9632
• 4f Dang T.-T, Abdellah I, Canac Y, Chauvin R. ChemCatChem 2011; 3: 1491
• 5a Rajabi J, Lorion MM, Ly VL, Liron F, Oble J, Prestat G, Poli G. Chem. Eur. J. 2014; 20: 1539
• 5b Lorion MM, Nahra F, Ly VL, Mealli C, Messaoudi A, Liron F, Oble J, Poli G. Chim. Oggi 2014; 32: 30
• 6 Chen MS, Prabagaran N, Labenz NA, White MC. J. Am. Chem. Soc. 2004; 126: 1346

The initial reaction conditions of this project were inspired by our work on direct intramolecular allylic amination. See:
• 7a Nahra F, Liron F, Prestat G, Mealli C, Messaoudi A, Poli G. Chem. Eur. J. 2009; 15: 11078
• 7b See also: Alexanian EJ, Lee C, Sorensen EJ. J. Am. Chem. Soc. 2005; 127: 7690
• 8 We have proposed the terms distocyclic and proxicyclic to unequivocally distinguish between β-H eliminations involving a hydrogen atom either on a linear fragment or on a cyclic structure, respectively.

For other examples of intramolecular aminopalladations followed by β-hydride elimination, see:
• 9a Malkov AV, Lee DS, Barlóg M, Elsegood MR. J, Kočovský P. Chem. Eur. J. 2014; 20: 4901
• 9b Weinstein AB, Schuman DP, Tan ZX, Stahl SS. Angew. Chem. Int. Ed. 2013; 52: 11867
• 9c Yang G, Shen C, Zhang W. Angew. Chem. Int. Ed. 2012; 51: 9141
• 9d Redford JE, McDonald RI, Rigsby KL, Wiensch JD, Stahl SS. Org. Lett. 2012; 14: 1242
• 9e Joosten A, Persson AK. Å, Millet R, Johnson MT, Bäckvall J.-E. Chem. Eur. J. 2012; 18: 15151

For other examples of intramolecular Pd(II)-catalyzed aminoacetoxylation in the presence of PhI(OAc)₂, see:
• 10a Chen S, Wu T, Liu G, Zhen X. Synlett 2011; 891
• 10b Hovelmann CH, Streuff J, Brelot L, Muniz K. Chem. Commun. 2008; 2334
• 10c Alexanian EJ, Lee C, Sorensen EJ. J. Am. Chem. Soc. 2005; 127: 7690

In the presence of H₂O₂ in AcOH, see:
• 10d Zhu H, Chen P, Liu G. Org. Lett. 2015; 17: 1485
• 10e Zhu H, Chen P, Liu G. J. Am. Chem. Soc. 2014; 136: 1766

For recent reports about the reversible aminopalladation, see:
• 11a Ref. 9d.
• 11b Wu T, Cheng J, Chen P, Liu G. Chem. Commun. 2013; 49: 8707
• 11c White PB, Stahl SS. J. Am. Chem. Soc. 2011; 133: 18594
• 12 It has to be noted that this kind of vinyl lactones (in particular five- or six-membered) are volatile and unstable at room temperature, see: Lumbroso A, Abermil N, Breit B. Chem. Sci. 2012; 3: 789
• 13 The oxidative Pd(II)-catalyzed conversion of terminally unsaturated alkenoic acids into the corresponding vinyl lactones via allylic C–H oxidation has been reported by Pietruska, see: Bischop M, Pietruszka J. Synlett 2011; 2689
• 14 Under conditions of method B, but in the absence of a Pd(II) catalyst, this same oxidative lactonization gave the desired compounds in very low yields (less than 10% after 48 h).
• 15 For the conversion of 1a into 3a in AcOH in the presence of PhI(OAc)₂ and catalytic TfOH, see: Kang Y.-B, Gade LH. J. Am. Chem. Soc. 2011; 133: 3658
• 16 The protocol in AcOH was not optimized. However, this result is consistent with a protocatalytic nature of alkene diacetoxylation in the presence of PhI(OAc)₂; see ref. 14.
• 17a Gormisky PE, White MC. J. Am. Chem. Soc. 2011; 133: 12584
• 17b Chen MS, Prabagaran N, Labenz NA, White MC. J. Am. Chem. Soc. 2005; 127: 6970
• 17c Fraunhoffer KJ, Prabagaran N, Sirois LE, White MC. J. Am. Chem. Soc. 2006; 128: 9032
• 17d Ammann SE, Rice GT, White MC. J. Am. Chem. Soc. 2014; 136: 10834

According to the present knowledge on this domain, the Pd(II)-to-Pd(IV) oxidation might take place prior to or after (ref. 6b) the oxypalladation step. See:
• 18a Pilarski LT, Selander N, Böse D, Szabó KJ. Org. Lett. 2009; 11: 5518
• 18b Alam R, Pilarski LT, Pershagen E, Szabó KJ. J. Am. Chem. Soc. 2012; 134: 8778
• 18c Check CT, Henderson WH, Wray BC, Eyden MJ. V, Stambuli JP. J. Am. Chem. Soc. 2011; 133: 18503
• 19 Powers DC, Ritter T. Nat. Chem. 2009; 1: 302
• 20 For a recent example of Pd(II)-catalyzed intramolecular acyloxylation–acetoxylation in the presence of PhI(OAc)₂, see: Li Y, Song D, Dong VM. J. Am. Chem. Soc. 2008; 130: 2962

For recent examples of intramolecular oxypalladation followed by β-hydride elimination, see:
• 21a Takenaka K, Akita M, Tanigaki Y, Takizawa S, Sasai H. Org. Lett. 2011; 13: 3506
• 21b Trend RM, Ramtohul YK, Stoltz BM. J. Am. Chem. Soc. 2005; 127: 17778
• 21c Hayashi T, Yamasaki K, Mimura M, Uozumi Y. J. Am. Chem. Soc. 2004; 126: 3036

For a similar by-product obtained after a Mizoroki–Heck coupling between in situ generated PhI and alkene, see:
• 22a Ref 4a.
• 22b Qu X, Sun P, Li T, Mao J. Adv. Synth. Catal. 2011; 353: 1061
• 22c Evdokimov NM, Kornienko A, Magedov IV. Tetrahedron Lett. 2011; 52: 4327
• 23 We assume that the Mizoroki–Heck process generates the iodide anion required for the iodolactonization. See: Liu H, Tan C-H. Tetrahedron Lett. 2007; 48: 8220
• 24 McDonald RI, Liu G, Stahl SS. Chem. Rev. 2011; 111: 2981
• 25 Lyons TW, Sanford MS. Chem. Rev. 2010; 110: 1147

The trans configuration (erythro) of 3e and the cis configuration (threo) of 3e′ were clearly attributed with the J ₃,₄ coupling constants in the ¹H NMR spectra, and compared with the data reported in the literature, see:
• 26a Pakuiski Z, Zamojski A. Tetrahedron 1995; 51: 871
• 26b Tiecco M, Testaferri L, Tingoli M, Bartoli D. Tetrahedron 1990; 46: 7139

For recent examples of oxypalladation followed by carbopalladation–β-hydride elimination, see:
• 27a Tietze L, Stecker F, Zinngrebe J, Sommer KM. Chem. Eur. J. 2006; 12: 8770
• 27b Tietze L, Sommer KM, Zinngrebe J, Stecker F. Angew. Chem. Int. Ed. 2005; 44: 257

For a definition of domino sequences in a catalytic transformation, see:
• 28a Poli G, Giambastiani G. J. Org. Chem. 2002; 67: 9456
• 28b Prestat G, Poli G. Chemtracts Org. Chem. 2004; 17: 97
• 29 Given the complexity of the crude ¹H NMR spectrum, we were not able to determinate the diastereomeric ratios for compounds 5 and 6. Although we did not optimize this domino sequence, the results still confirm our conclusions concerning the involvement of the cyclic OxPI intermediate.
• 30a General Procedures; Conditions A: In a sealed tube, under an argon atmosphere, were added the carboxylic acid (1.0 equiv), Pd(OAc)₂ (0.1 equiv), bis-sulfoxide ligand (0.15 equiv), p-phenylbenzoquinone (1.07 equiv), NaOAc (1.0 equiv) and CH₂Cl₂ (0.5 M). The tube was sealed and the reaction was allowed to stir at 45 °C. After 24 h, the reaction mixture was filtered on a plug of celite. The filtrate was treated with a sat. aq solution of 5% K₂CO₃ and the aqueous layer was extracted with CH₂Cl₂ (3 ×). The combined organic layers were dried over anhyd MgSO₄, filtered and concentrated under reduced pressure. Purification by flash silica gel column chromatography afforded the desired vinyl lactone. Analytical Data for 2b: Yield: 59%; colorless oil. ¹H NMR (300 MHz, CDCl₃): δ = 5.86 (ddd, J = 17.1, 10.5, 6.0 Hz, 1 H), 5.33 (dt, J = 17.2, 1.2 Hz, 1 H), 5.22 (dt, J = 10.5, 1.1 Hz, 1 H), 4.87–4.95 (m, 1 H), 2.50 (ddd, J = 8.0, 6.9, 1.1 Hz, 2 H), 2.31–2.46 (m, 1 H), 1.87–2.07 (m, 1 H). These data are in good agreement with those reported in the literature (ref. 11). Conditions B: In a sealed tube, under an argon atmosphere, were added the carboxylic acid (1.0 equiv), Pd(OAc)₂ (0.1 equiv), bis-sulfoxide ligand (0.15 equiv), iodobenzene diacetate (2.1 equiv), NaOAc (1.0 equiv) and CH₂Cl₂ (0.5 M). The tube was sealed and the reaction was allowed to stir at 45 °C for 24 h. The mixture was filtered over a small pad of celite. The filtrate was treated with a sat. aq solution of 5% K₂CO₃ and the aqueous layer was extracted with CH₂Cl₂ (3 ×). The combined organic layers were dried over anhyd MgSO₄, filtered and concentrated under reduced pressure. Purification by flash silica gel column chromatography afforded the acetoxylated product. Analytical Data for 3b: yield: 41%; yellow oil. ¹H NMR (300 MHz, CDCl₃): δ = 4.45–4.53 (m, 1 H), 4.18 (dd, J = 12.0, 3.8 Hz, 1 H), 4.12 (dd, J = 12.0, 5.8 Hz, 1 H), 2.30–2.74 (m, 2 H), 2.04 (s, 3 H), 1.70–2.00 (m, 3 H), 1.50–1.71 (m, 1 H).
• 30b These data are in good agreement with those reported in the literature: Ha HJ, Park YS, Park GS. ARKIVOC 2001; (i): 55