[101849-67-6]  · C8H17ClSn  · (Z)-5-Chloro-3-trimethylstannyl-2-pentene  · (MW 267.36)

(cyclopentane annulations;2,3 bifunctional reagent;4-6 spirotetrahydrofuran synthesis7)

Alternate Name: [1-(2-chloroethyl)-1-propenyl]trimethylstannane.

Physical Data: bp 40-50 °C/0.3 mmHg.8

Analysis of Reagent Purity: 1H NMR.8

Preparative Methods: by the addition of Lithium Phenylthio(trimethylstannyl)cuprate to ethyl 2-pentynoate,9 followed by stereospecific deconjugation (eq 1)10,11 to afford ethyl (Z)-3-trimethylstannyl-3-pentynoate as a single isomer.10 Reduction and conversion to the chloride provides the title reagent (eq 2).8

Purification: by distillation.8

Handling, Storage, and Precautions: organostannanes should be considered as toxic compounds.12 This reagent should be handled in a well-ventilated fume hood and gloves should be worn to prevent contact with the skin.

Spirotetrahydrofuran Synthesis.

See also 4-Chloro-2-trimethylstannyl-1-butene. Treatment of the title reagent with Methyllithium results in complete formation of the (Z)-vinyllithium reagent. Addition to cyclohexanone affords a mixture of the chloro alcohol (31%) and the spirotetrahydrofuran (40%) (eq 3).8

It is interesting to note that treatment of (E)-5-chloro-3-trimethylstannyl-2-pentene under these conditions (MeLi, THF, -78 °C, cyclohexanone or benzaldehyde) provided only the ethylidenecyclopropane (isolated as a chloro sulfide by treatment with 2,4-Dinitrobenzenesulfenyl Chloride).8 A 1,2-addition product was not isolated.

[3 + 2] Annulations.

See also 4-Chloro-2-trimethylstannyl-1-butene. (Z)-5-Chloro-3-trimethylstannyl-2-pentene has been used in a two-step process as a cyclopentane annulation reagent.8,13 (Z)-5-Chloro-3-lithio-2-pentene (see above) is treated with Magnesium Bromide in THF to provide the vinyl Grignard. The cuprate derived from this adds in a 1,4-fashion to cycloalkenones to afford the chloro ketone (as a mixture of diastereomers when R &neq; H). Closure to the cis-fused bicyclic ketone is accomplished by an intramolecular alkylation (Table 1; eq 4).8

This methodology has been used to accomplish the total synthesis of (±)-oplopanone, (±)-8-epi-oplopanone, and (±)-anhydro-oplopanone (eq 5).8,13

1. Piers, E. PAC 1988, 60, 107.
2. Panek, J. S.; Jain, N. F. JOC 1993, 58, 2345.
3. Mehta, G.; Karra, S. R. TL 1991, 32, 3215.
4. De Lombaert, S.; Nemery, I.; Roekens, B.; Carretero, J. C.; Kimmel, T.; Ghosez, L. TL 1986, 27, 5099.
5. Knapp, S.; O'Connor, U. Mobilio, D. TL 1980, 21, 4557.
6. Trost, B. M. AG(E) 1986, 25, 1.
7. Boivin, T. L. B. T 1987, 43, 3309.
8. Piers, E.; Gavai, A. V. JOC 1990, 55, 2380.
9. Piers, E.; Chong, J. M.; Morton, H. E. T 1989, 45, 363.
10. Piers, E.; Gavai, A. V. JOC 1990, 55, 2374.
11. Piers, E.; Gavai, A. V. CC 1985, 1241.
12. Neumann, W. P. The Organic Chemistry of Tin; Interscience: New York, 1970; pp 230-237.
13. Piers, E.; Gavai, A. V. TL 1986, 27, 313.

Joseph S. Warmus

Parke-Davis Pharmaceuticals, Ann Arbor, MI, USA

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