[85370-32-7]  · C7H15ClSn  · 4-Chloro-2-trimethylstannyl-1-butene  · (MW 253.34)

(precursor of a number of bifunctional reagents,1,2 which have been employed for effecting synthetically useful methylenecyclopentane annulation sequences1-4)

Physical Data: colorless liquid, distillation temperature (bulb-to-bulb) 55-60 °C/12 mmHg.

Solubility: insol H2O; sol THF, Et2O, CHCl3, and other common organic solvents.

Preparative Methods: 4-chloro-2-trimethylstannyl-1-butene (3) is readily prepared from the commercially available butynol (1). Regioselective addition of Me3SnCu.Me2S5 (see Trimethylstannylcopper-Dimethyl Sulfide) to (1) provides6 3-trimethylstannyl-3-buten-1-ol (2), which upon reaction with Ph3P-CCl4 in the presence of Et3N affords (3) (eq 1). This preparative sequence can be carried out on a reasonably large scale (0.2 mol) and produces overall yields of about 50%.

Handling, Storage, and Precautions: when stored in a freezer under an atmosphere of argon the reagent is stable for extended periods of time (years). It should be distilled prior to use and handled only in a well-ventilated fume hood.

Conversion into Bifunctional Reagents.

Reagent (3) is an effective precursor to a number of synthetically useful bifunctional reagents. Transmetalation7 of (3) with MeLi in THF at low temperature provides the novel reagent (4) (eq 2).1 The latter species is stable in THF if the temperature of the solution is kept below -50 °C. At higher temperatures, (4) self-destructs,2 presumably8b to produce LiCl and methylenecyclopropane. Treatment of (4) with MgBr2,1c CuBr.Me2S (0.5 equiv),2 CuCN,1b,c or PhSCu1b,c produces, respectively, the Grignard reagent (5), the homocuprate (6), and the heterocuprates (7) and (8).

Methylenecyclopentane Annulations.

Reagents (4)-(8) serve as useful bifunctional species in a variety of contexts. The lithio reagent (4) has been employed for the direct conversion of aldehydes and ketones into substituted 3-methylenetetrahydrofurans (eq 3)1a,c and of a,b-unsaturated N,N,N-trimethylhydrazides into functionalized methylenecyclopentanes (eq 4).1a,c

More importantly, reagents (5)-(8) have been employed effectively in the development of a synthetically useful methylenecyclopentane annulation method involving a,b-unsaturated ketones as substrates.9 The two required steps, involving conjugate addition of the 2-(4-chloro-1-butenyl) group to the enone and subsequent intramolecular alkylation, may be carried out separately (eqs 5, 6 and 8)1-3 or via a one-pot protocol (eq 7).4 The importance of the one-pot process is particularly illustrated by the conversion of (11) into (12) (eq 7), since attempted intramolecular alkylation of (13) gives very poor yields of (12).4 Although, normally, reagents (5)-(8) may be successfully interchanged for the conjugate addition step, it has been reported2 that attempted additions of reagents (7) and (8) to the enone (14) are singularly unsuccessful. It is worth noting that substances (9), (10), (12), and (15) have played central roles in the total synthesis of a number of terpenoid natural products: (±)-D9(12)-capnellene,1c,3a (±)-pentalenene,3b,c (±)-methyl cantabrenonate,4 (±)-methyl epoxycantabronate,4 and (+)-ceroplastol I.2

Related Reagents.

By use of chemistry similar to that outlined above, 5-Chloro-2-trimethylstannyl-1-pentene (16)6 and (Z)-5-chloro-3-trimethylstannyl-2-pentene (20)8 have also been employed as precursors of useful bifunctional reagents. The Grignard reagent (18) and the cuprate (19), both obtained from (16) via the lithio species (17), can be used to carry out efficient methylenecyclohexane annulation sequences (eq 9).10,11 Similarly, (Z)-ethylidenecyclopentane annulations (eq 10)8b can be accomplished by utilizing reagent (22), which is derived from (20) via (21). These annulation methods have found appreciable use in natural product synthesis.8b,10c,12

1. Piers, E.; Karunaratne, V. (a) JOC 1983, 48, 1774. (b) CC 1983, 935. (c) T 1989, 45, 1089.
2. Paquette, L. A.; Wang, T.-Z.; Vo, N. H. JACS 1993, 115, 1676.
3. Piers, E.; Karunaratne, V. (a) CJC 1984, 62, 629. (b) CC 1984, 959. (c) CJC 1989, 67, 160.
4. Piers, E.; Renaud, J. (a) CC 1990, 1324. (b) S 1992, 74.
5. (a) Piers, E.; Chong, J. M.; Morton, H. E. TL 1981, 22, 4905. (b) Piers, E.; Morton, H. E.; Chong, J. M. CJC 1987, 65, 78.
6. Piers, E.; Chong, J. M. (a) CC 1983, 934. (b) CJC 1988, 66, 1425.
7. Reich, H. J.; Borst, J. P.; Coplien, M. B.; Phillips, N. H. JACS 1992, 114, 6577 and citations therein.
8. Piers, E.; Gavai, A. V. (a) CC 1985, 1241. (b) JOC 1990, 55, 2380.
9. For annulation sequences involving organocopper(I) reagents related in structure to (6)-(8), see Semmelhack, M. F.; Yamashita, A.; Tomesch, J. C.; Hirotsu, K. JACS 1978, 100, 5565 and Magnus, P.; Quagliato, D. JOC 1985, 50, 1621.
10. (a) Piers, E.; Yeung, B. W. A. JOC 1984, 49, 4567. (b) Piers, E.; Yeung, B. W. A.; Fleming, F. F. CJC 1993, 71, 280. (c) Piers, E.; Yeung, B. W. A.; Rettig, S. J. T 1987, 43, 5521.
11. Piers, E.; Roberge, J. Y. TL 1991, 32, 5219.
12. (a) Piers, E.; Yeung, B. W. A. CJC 1986, 64, 2475. (b) Piers, E.; Wai, J. S. M. CC 1987, 1342. (c) Piers, E.; Wai, J. S. M. CC 1988, 1245. (d) Piers, E.; Fleming, F. F. CC 1989, 1665. (e) Piers, E.; Roberge, J. Y. TL 1992, 33, 6923.

Edward Piers & Christine Rogers

University of British Columbia, Vancouver, BC, Canada

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.