6034
J. Org. Chem. 1997, 62, 6034-6040
Copper Chloride-Catalyzed and Hydrochloric Acid-Mediated Chemoselective Protiodestannylations of Alkyl (Z)- or (E)-2,3-Bis(trimethylstannyl)-2-alkenoates. Stereoselective Preparation of Alkyl (E)- and (Z)-3-Trimethylstannyl-2-alkenoates Edward Piers,* Ernest J. McEachern, and Miguel A. Romero Department of Chemistry, University of British Columbia, 2036 Main Mall, University Campus, Vancouver, British Columbia, Canada V6T 1Z1 Received April 30, 1997X
Treatment of alkyl (Z)-2,3-bis(trimethylstannyl)-2-alkenoates (7) with a catalytic amount of copper(I) chloride in N,N-dimethylformamide (DMF) containing a small quantity of water provides very goodto-excellent yields of alkyl (E)-3-trimethylstannyl-2-alkenoates (1). On the other hand, stirring of solutions of alkyl (Z)- (7) or (E)-2,3-bis(trimethylstannyl)-2-alkenoates (8) in DMF containing dilute hydrochloric acid produces, efficiently, alkyl (Z)-3-trimethylstannyl-2-alkenoates (2). Introduction
Scheme 1
The synthetic uses of alkyl (E)- and (Z)-3-trialkylstannnyl-2-alkenoates of general structures 1 and 2, along with those of substances readily derived from 1 and 2, are well established.1,2 Up to the present time, the
most convenient and efficient methods for preparing 1 and 2 in a stereocontrolled fashion entail treatment of R,β-alkynic esters with suitable trialkylstannylcopper(I) reagents under carefully defined reaction conditions.1a,3 Examples involving the production of diastereomeric * Telephone: 604-822-3219. Fax: 604-822-2847. E-mail: epier@ unixg.ubc.ca. X Abstract published in Advance ACS Abstracts, August 1, 1997. (1) (a) Piers, E.; Chong, J. M.; Gustafson, K.; Andersen, R. J. Can. J. Chem. 1984, 62, 1. (b) Piers, E.; Gavai, A. V. J. Chem. Soc., Chem. Commun. 1985, 1241. (c) Piers, E.; Gavai, A. V. Tetrahedron Lett. 1986, 27, 313. (d) Piers, E.; Friesen, R. W. J. Org. Chem. 1986, 51, 3405. (e) Piers, E.; Friesen, R. W. Can. J. Chem. 1987, 65, 1681. (f) Piers, E.; Lu, Y.-F. J. Org. Chem. 1988, 53, 926. (g) Piers, E.; Llinas-Brunet, M. J. Org. Chem. 1989, 54, 1483. (h) Piers, E.; Gavai, A. V. J. Org. Chem. 1990, 55, 2374. (i) Piers, E.; Gavai, A. V. J. Org. Chem. 1990, 55, 2380. (j) Piers, E.; Friesen, R. W. Can. J. Chem. 1992, 70, 1204. (k) Piers, E.; Friesen, R. W.; Rettig, S. J. Can. J. Chem. 1992, 70, 1385. (l) Piers, E.; Roberge, J. Y. Tetrahedron Lett. 1992, 33, 6923. (m) Piers, E.; Ellis, K. A. Tetrahedron Lett. 1993, 34, 1875. (n) Piers, E.; Wong, T. J. Org. Chem. 1993, 58, 3609. (o) Piers, E.; Llinas-Brunet, M.; Oballa, R. M. Can. J. Chem. 1993, 71, 1484. (p) Piers, E.; Wai, J. S. M. Can. J. Chem. 1994, 72, 146. (q) Piers, E.; Coish, P. D. Synthesis 1995, 47. (r) Piers, E.; McEachern, E. J.; Burns, P. A. J. Org. Chem. 1995, 60, 2322. (s) Piers, E.; McEachern, E. J.; Romero, M. A. Tetrahedron Lett. 1996, 37, 1173. (t) Piers, E.; Romero, M. A. J. Am. Chem. Soc. 1996, 118, 1215. (u) Piers, E.; McEachern, E. J. Synlett 1996, 1087. (2) (a) Harusawa, S.; Osaki, H.; Takemura, S.; Yoneda, R.; Kurihara, T. Tetrahedron Lett. 1992, 33, 2543. (b) Dodd, D. S.; Pierce, H. D. Jr.; Oehlschlager, A. C. J. Org. Chem. 1992, 57, 5250. (c) Paquette, L. A.; Lassalle, G. Y.; Lovely, C. J. J. Org. Chem. 1993, 58, 4254. (d) Paquette, L. A.; Deaton, D. N.; Endo, Y.; Poupart, M.-A. J. Org. Chem. 1993, 58, 4262. (e) Harusawa, S.; Takemura, S.; Osaki, H.; Yoneda, R.; Kurihara, T. Tetrahedron 1992, 49, 7657. (f) De Brabander, J.; Vandewalle, M. Synthesis 1994, 855. (g) Elbaum, D.; Porco, J. A. Jr.; Stout, T. J.; Clardy, J.; Schreiber, S. L. J. Am. Chem. Soc. 1995, 117, 211. (h) Reginato, G.; Capperucci, A.; Degl’Innocenti, A.; Pecchi, S. Tetrahedron 1995, 51, 2129. (i) Hutzinger, M. W.; Oehlschlager, A. C. J. Org. Chem. 1995, 60, 4595. (3) (a) Piers, E.; Morton, H. E. J. Org. Chem. 1980, 45, 4263. (b) Piers, E.; Chong, J. M.; Morton, H. E. Tetrahedron Lett. 1981, 22, 4905. (c) Piers, E.; Chong, J. M.; Morton, H. E. Tetrahedron 1989, 45, 363. (d) Piers, E.; Tillyer, R. D. J. Org. Chem. 1988, 53, 5366. (e) Piers, E.; Wong, T.; Ellis, K. A. Can. J. Chem. 1992, 70, 2058.
S0022-3263(97)00769-X CCC: $14.00
3-trimethylstannyl-2-alkenoates are shown in Scheme 1.3e Thus, reaction of ethyl 4-cyclohexyl-2-butynoate (3) with lithium (trimethylstannyl)(cyano)cuprate4 in tetrahydrofuran (THF) at -48 to 0 °C, followed by addition of aqueous NH4Cl-NH4OH (pH ∼8), provided the (Z)-3trimethylstannyl-2-alkenoate 4, accompanied by small amounts (∼5% total) of the corresponding E isomer and ethyl (E)-4-cyclohexyl-2,3-bis(trimethylstannyl)-2-butenoate. Purification of this material by a combination of flash chromatography5 and distillation afforded 4 in 81% yield.3e On the other hand, treatment (THF, -78 °C) of 3 with the same cuprate reagent in the presence of dry ethanol, followed by a suitable workup and chromatographic separation of the small amount (
