Ring-Closing Metathesis Reactions of Acyloxysulfones: Synthesis of γ-Alkylidene Butenolides

Abstract

An acyloxysulfone ring-closing metathesis/sulfone elimination sequence has been developed for the preparation of various γ-alkylidene butenolides. The elimination is proposed to proceed via an E1cb mechanism leading to (Z)-γ-alkylidene butenolides as the major products.

Key words

ring-closing metathesis - polyene metathesis - acyloxysulfone metathesis - E1cb elimination - γ-alkylidene butenolide

• References and Notes

• 1a Alkene Metathesis in Organic Synthesis . Fürstner A. Springer; Berlin: 1998
• 1b Handbook of Metathesis . Grubbs RH. Wiley-VCH; Weinheim: 2003
• 2a For a recent review see: Vougioukalakis GC, Grubbs RH. Chem. Rev. 2010; 110: 1746
• 2b See also: Urbina-Blanco CA, Guidone S, Nolan SP, Cazin CS. J. Ruthenium-Indenylidene and Other Alkylidene Containing Olefin Metathesis Catalysts. In Olefin Metathesis: Theory and Practice . Grela K. John Wiley & Sons, Inc; Hoboken: 2014
• 3a Fürstner A. Angew. Chem. Int. Ed. 2000; 39: 3012
• 3b Metathesis in Natural Product Synthesis . Cossy J, Arseniyadis S, Meyer C. Wiley-VCH; Weinheim: 2010
• 4 Chatterjee AK, Choi T.-L, Sanders DP, Grubbs RH. J. Am. Chem. Soc. 2003; 125: 11360
• 5 For a recent review see: Wojtkielewicz A. Curr. Org. Synth. 2013; 10: 43
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• 7 O’Neil GW, Moser DJ, Volz EO. Tetrahedron Lett. 2009; 50: 7355
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• 11 Crimmins MT, Zhang Y, Diaz FA. Org. Lett. 2006; 8: 2369
• 12 For a discussion on sulfone/ruthenium interactions in RCM, see: Paquette LA, Fabris F, Tae J, Gallucci JC, Hofferberth JE. J. Am. Chem. Soc. 2000; 122: 3391
• 13 The stereochemistry of the major isomer was assigned as Z by comparison to previously reported spectral data: Uchiyama M, Ozawa H, Takuma K, Matsumoto Y, Yonehara M, Hiroya K, Sakamoto T. Org. Lett. 2006; 8: 5517
• 14 For another report of γ-alkylidene butenolide synthesis by E1cb elimination, see: Shing TK. M, Tsui H-C, Zhou Z.-H. J. Org. Chem. 1995; 60: 3121
• 15 Gronert S. J. Am. Chem. Soc. 1992; 114: 2349
• 16 See: Novák P, Pour M, Špulák M, Votruba I, Kotora M. Synthesis 2008; 3465 ; and references cited therein

For other examples of butenolide synthesis by RCM, see:
• 17a Mao B, Geurts K, Fañanás-Mastral M, van Zijl AW, Fletcher SP, Minnaard AJ, Feringa BL. Org. Lett. 2011; 13: 948
• 17b Fujii M, Fukumura M, Hori Y, Hirai Y, Akita H, Nakamura K, Toriizuka K, Ida Y.-S. Tetrahedron: Asymmetry 2006; 17: 2292
• 18 For an alternative synthesis of 14 and other γ-arylidenebutenolides by elimination with triethylamine, see: Pohmakotr M, Tuchinda P, Premkaisorn P, Reutrakul V. Tetrahedron 1998; 54: 11297

An E1cb mechanism is likely also operative in the following reports of γ-alkylidene butenolide syntheses:
• 19a Takao K.-I, Yasui H, Yamamoto S, Sasaki D, Kawasaki S, Watanabe G, Tadano K.-I. J. Org. Chem. 2004; 69: 8789
• 19b Hjelmgaard T, Persson T, Rasmussen TB, Givskov M, Nielsen J. Bioorg. Med. Chem. 2003; 11: 3261
• 19c Wang L, Zhu W. Tetrahedron Lett. 2013; 54: 6729
• 20a Compound 14: see ref. 11.
• 20b Compound 15: Font J, Ortuno RM, Sanchez-Ferrando F, Segura C, Terris N. Synth. Commun. 1989; 19: 2977
• 20c Compounds 16 and 17: Kanemasa S, Nakagawa N, Suga H, Tsuge O. Bull. Chem. Soc. Jpn. 1989; 62: 171
• 20d Compound 19: Sorg A, Siegel K, Brueckner R. Synlett 2004; 321
• 21 The stereochemistry of the major isomer 18 was assigned as Z by NOE NMR analysis (Figure 1):
• 22 Jeon H.-S, Yeo JE, Jeong YC, Koo S. Synthesis 2004; 2813
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• 24 Scholl M, Ding S, Lee CW, Grubbs RH. Org. Lett. 1999; 1: 953
• 25 Compound 25 was prepared from sulfone 26 in three steps (Scheme 8):
• 26 CRC Handbook of Chemistry and Physics . 77th ed., Lide DR. CRC Press; Boca Raton: 1997
• 27 Perez GV, Perez AL. J. Chem. Ed. 2000; 77: 910
• 28 Typical Acyloxysulfone RCM Procedure; 5-[Phenyl(phenylsulfonyl)methyl]furan-2(5H)-one (8): To a solution of compound 2 (92 mg, 0.3 mmol) in degassed toluene (10 mL) at 80 °C was added catalyst Ru-II (3 × 6 mg, 0.02 mmol) over 18 h. The reaction was then cooled to r.t. and concentrated in vacuo. Purification by flash column chromatography on silica (hexanes–EtOAc, 4:1 to 1:1) gave compound 8 (54 mg, 64%) as an oil. ¹H NMR (300 MHz, CDCl₃): δ (mixture of diastereomers) = δ 7.93 (d, J = 9.5 Hz, 1 H), 7.70 (d, J = 7.6 Hz, 2 H), 7.66 (d, J = 5.7 Hz, 1 H), 7.60–7.53 (m, 2 H), 7.50 (d, J = 7.6 Hz, 2 H), 7.44 (t, J = 7.8 Hz, 2 H), 7.36–7.32 (m, 4 H), 7.28–7.25 (m, 3 H), 7.21–7.17 (m, 3 H), 7.08 (d, J = 12.3 Hz, 2 H), 6.17 (dd, J = 9.5, 2.7 Hz, 1 H), 6.11 (dd, J = 5.7, 1.7 Hz, 1 H), 6.00 (d, J = 7.0 Hz, 1 H), 5.96 (d, J = 6.2 Hz, 1 H), 4.52 (d, J = 6.2 Hz, 1 H), 4.23 (d, J = 7.1 Hz, 1 H). ¹³C NMR (125 MHz, CDCl₃): δ (mixture of diastereomers) = 171.6, 171.1, 154.4, 153.5, 137.8, 136.5, 134.2, 130.4, 130.0, 129.7, 129.5, 129.2, 129.0, 128.9, 128.8, 128.7, 127.7, 123.3, 122.6, 79.7, 79.6, 73.5, 72.8. General One-Pot RCM/Elimination Procedure: (Z)-5-(3-Phenylpropylidene)furan-2(5H)-one (18). To a solution of compound 5 (0.21 g, 0.55 mmol) in toluene (30 mL) at 80 °C was added batchwise catalyst Ru-II (3 × 12 mg, 0.04 mmol) over 18 h. The reaction was then cooled to 0 °C before adding Et₃N (0.47 mL, 3.4 mmol) and the mixture was allowed to slowly warm to r.t. over 12 h. The reaction was quenched with H₂O (10 mL) and extracted with CH₂Cl₂ (2 × 10 mL). The combined organic extracts were dried over MgSO₄, filtered, and concentrated in vacuo. Purification by flash column chromatography on florisil (hexanes–EtOAc, 4:1) gave 18 (59 mg, 54%) as a 5:1 mixture of Z/E isomers. Spectral data for the major isomer: IR (ATR): 1772, 1732, 1496, 1151, 1074, 700 cm^–1. ¹H NMR (500 MHz, CDCl₃): δ = 7.35–7.30 (m, 3 H), 7.26–7.23 (m, 3 H), 6.18 (d, J = 5.5 Hz, 1 H), 5.31 (t, J = 7.7 Hz, 1 H), 2.86–2.75 (m, 4 H). ¹³C NMR (125 MHz, CDCl₃): δ = 170.0, 150.0, 143.5, 140.7, 128.5, 128.4, 126.3, 119.3, 116.2, 34.9, 27.9.