[89045-21-6]  · C8H17ClSn  · 5-Chloro-2-trimethylstannyl-1-pentene  · (MW 267.38)

(cyclohexane annulation; bifunctional reagent;2-4 intramolecular Stille coupling5)

Alternate Name: (4-chloro-1-methylenebutyl)trimethylstannane.

Physical Data: bp 55-60 °C/12 mmHg.6

Analysis of Reagent Purity: GLC, 1H NMR.6

Preparative Methods: treatment of commercially available 5-chloro-1-pentyne with Me3SnCu.Me2S (see Trimethylstannylcopper-Dimethyl Sulfide) in THF at -68 °C in the presence of excess MeOH provides a 9:1 mixture of 5-chloro-2-trimethylstannyl-1-pentene and 5-chloro-1-trimethylstannyl-1-pentene.6-8 Slow column chromatography removes the minor product.6

Purification: silica gel chromatography (pet. ether) followed by distillation.6

Handling, Storage, and Precautions: organostannanes should be considered as toxic compounds.9 This reagent should be handled in a well-ventilated fume hood and gloves should be worn to prevent contact with the skin.


See also (Z)-5-Chloro-3-trimethylstannyl-2-pentene and 4-Chloro-2-trimethylstannyl-1-butene. Addition of 5-chloro-2-lithio-1-pentene, prepared from the title reagent and MeLi at -78 °C, to cyclohexanone affords the chloro alcohol in 84% yield (eq 1). At higher temperatures (-50 °C), decomposition of this product occurs.10

Methylenecyclohexane Annulations.

Alkylation of the N,N-dimethylhydrazone of a cyclohexanone with 5-iodo-2-trimethylstannyl-1-pentene (prepared from the title reagent by treatment with NaI, acetone, 84%) and immediate cleavage of the hydrazone provides a ketovinylstannane. Conversion of the stannane to the iodide and metal-halogen exchange completes the annulation, affording the allylic, angular alcohol (eq 2).11

Methylenecyclohexanes have been prepared from enones in a two-step sequence by means of a cuprate addition followed by an intramolecular alkylation. The cuprate is prepared from 5-chloro-2-lithio-1-pentene (see above) either by treatment with Tri-n-butylphosphine and copper(I) bromide-dimethyl sulfide in THF or with Magnesium Bromide (to make the Grignard) followed by CuBr.Me2S.10 Addition of the cuprate to an enone occurs to give a mixture of diastereomers (R &neq; H). Intramolecular alkylation is effected by Potassium Hydride in THF to give the kinetic products, which possess a cis ring fusion. These may be equilibrated (MeONa, MeOH) to provide the thermodynamically favored product when R = H (Table 1) (eq 3).10

This methodology has been used to synthesize the sesquiterpenoids (±)-axamide-1 and (±)-axisonitrile-1,12,13 and the sesterterpenoid (±)-palauolide (eqs 4 and 5).14

A trimethylstannyl group has been used as a removable anchoring group in an annulation sequence directed towards enantiomerically pure clerodane diterpenoids (eq 6).15

Intramolecular Stille Couplings.

Bicyclic dienes have been prepared from the alkylated keto acetal (see eq 2) by formation of the enol triflate, followed by palladium-catalyzed Stille coupling (eq 7).7,16

Related Reagents.

4-Chloro-2-trimethylstannyl-1-butene; (Z)-5-Chloro-3-trimethylstannyl-2-pentene.

1. Piers, E. PAC 1988, 60, 107.
2. De Lombaert, S.; Nemery, I.; Roekens, B.; Carretero, J. C.; Kimmel, T.; Ghosez, L. TL 1986, 27, 5099.
3. Knapp, S.; O'Connor, U.; Mobilio, D. TL 1980, 21, 4557.
4. Trost, B. M. AG(E) 1986, 25, 1.
5. Stille, J. K.; Tanaka, M. JACS 1987, 109, 3785.
6. Piers, E.; Chong, J. M. CJC 1988, 66, 1425.
7. Piers, E.; Friesen, R. W.; Keay, B. A. T 1991, 47, 4555.
8. Piers, E.; Chong, J. M. CC 1983, 934.
9. Neumann, W. P. The Organic Chemistry of Tin; Interscience: New York, 1970; pp 230-237.
10. Piers, E.; Yeung, B. W. A. JOC 1984, 49, 4567.
11. Piers, E.; Marais, P. C. TL 1988, 29, 4053.
12. Piers, E.; Yeung, B. W. A. CJC 1986, 64, 2475.
13. Piers, E.; Yeung, B. W. A.; Rettig, S. J. T 1987, 43, 5521.
14. Piers, E.; Wai, J. S. M. CC 1987, 1342.
15. Piers, E.; Roberge, J. Y. TL 1991, 32, 5219.
16. Piers, E.; Friesen, R. W.; Keay, B. A. CC 1985, 809.

Joseph S. Warmus

Parke-Davis Pharmaceuticals, Ann Arbor, MI, USA

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