Trimethylstannane1

Me3SnH

[1631-73-8]  · C3H10Sn  · Trimethylstannane  · (MW 164.84)

(hydrostannation of alkenes and alkynes;2 radical hydrogen source;3 Me3SnLi precursor4)

Alternate Name: trimethyltin hydride.

Physical Data: bp 59-60 °C; d 1.477 g cm-3.

Solubility: sol common organic solvents; slightly sol H2O; insol NH3.

Form Supplied in: not commercially available.

Analysis of Reagent Purity: best analyzed by 1H NMR (C6D6).

Preparative Method: synthesized by the reaction of Lithium Aluminum Hydride with Chlorotrimethylstannane in ethereal solvents.5 Highest yields are obtained by using high boiling solvents such as bis(2-ethoxyethyl) ether.6

Purification: fractional distillation from LiAlH4.

Handling, Storage, and Precautions: unstable to oxidative and photolytic processes; best used immediately upon synthesis. Neat compound can be stored up to a month in a 0 to -20 °C refrigerator, under an inert atmosphere (N2 or Ar), protected from light. Organostannanes are toxic and should only be used in a well-ventilated hood. All glassware should be rinsed in a KOH/EtOH bath during cleaning.

Hydrostannation.

One of the primary uses of Me3SnH is for the hydrostannation of p-bonds. Addition of tin hydride can proceed via either a radical or an ionic pathway, depending on the reaction conditions and the substituents adjacent to the p-bond. Hydrostannation can also be mediated by a Pd0 catalyst. Hydrostannation of terminal alkynes can form three products (eq 1).2 The major product of the ionic pathway is the a-stannane, formed by addition of the trimethyltin moiety at the most substituted position.7 Radical hydrostannation typically affords a mixture of the cis-b- and trans-b-products, with the latter predominating.7 The palladium-mediated reaction can form any of the above products. The stereochemistry of the product can vary with the substituents on the alkyne. A striking example of this is the palladium-mediated hydrostannation of alkynic esters versus alkynic ketones.8 The ester gives predominantly syn (kinetic) addition, while the ketone gives predominantly anti (thermodynamic) addition. Allenes can be hydrostannated under either radical or palladium-catalyzed conditions, but typically lead to a regio- and stereochemical mixture of products.9

1,1-Distannyl-1-alkenes, formed by thermal radical hydrostannation of 1-stannyl-1-alkynes (eq 2), can be used to generate a-stannylvinyl anions upon treatment with Methyllithium.10 The anion can then be treated with electrophiles to form stereochemical mixtures of alkylated products (eq 3). The corresponding bis(tributylstannyl)alkene selectively affords the (E)-product. Addition of 2 equiv of methyllithium and electrophile forms the dialkylated product (eqs 4 and 5). Butyllithium cannot be used in this reaction due to alkyl exchange equilibria between tin and lithium.

Hydrostannation of alkenes affords alkyltins. For example, (E)-2,3-disubstituted propenoates can be irradiated with a mercury lamp for 4.5 h in the presence of trimethyltin hydride to give the b-stannane (eq 6).11 In this case, use of thermal free radical conditions (AIBN, 70 °C) causes reduced yields (~25%).11

Trimethylstannyllithium.

Treatment of trimethyltin hydride with LDA affords Trimethylstannyllithium, which can be used in nucleophilic reactions.12 While less convenient than the Me6Sn2/MeLi generation of Me3SnLi, this approach is also less expensive and affords fewer tin byproducts. Nucleophilic attack of trimethylstannyllithium on geminal dibromoalkenes gives the distannyl product in good yield.13 Use of the analogous dichloro alkene gives only Me6Sn2 and an alkyne. Treatment of Me3SnLi with t-Butyldimethylchlorosilane affords the silylstannane (eq 7), which can be added across an alkyne in the presence of Pd0 (eq 8).4

Reaction of trimethyltin hydride with a cuprate in THF at -78 °C forms the stannylcuprate, which will undergo conjugate additions.14 Trimethylstannyllithium will also undergo conjugate addition with enones (eq 9).15,16 After protection of the carbonyl group as an enamine, the trimethylstannyl group can be transmetalated to the alkyllithium with MeLi. Bu3SnH can also be used for this reaction.

Radical Reductions.

Alkyl halides are reduced with trimethyltin hydride in the presence of radical initiators, such as 1,1-Azobis-1-cyclohexanenitrile (ACHN).3 Tributyltin hydride will also work in this reaction.

Related Reagents.

Hexamethyldistannane; Tri-n-butylstannane; Triphenylstannane.


1. (a) Pereyre, M.; Quintard, J.-P.; Rahm, A. Tin in Organic Synthesis; Butterworths: London, 1987. (b) Davies, A. G.; Smith, P. J. In Comprehensive Organometallic Chemistry; Pergamon: Oxford, 1982; Chapter 11. (c) Ingham, R. K.; Rosenberg, S. D.; Gilman, H. CRV 1960, 60, 459. (d) Kuivila, H. G. S 1970, 499.
2. Leusink, A. J.; Budding, H. A.; Drenth, W. JOM 1967, 9, 295.
3. Mitchell, T. N.; Belt, H. J. JOM 1990, 386, 167.
4. Chenard, B. L.; Van Zyl, C. M. JOC 1986, 51, 3561.
5. Finholt, A. E.; Bond, A. C., Jr.; Wilzbach, K. E.; Schlesinger, H. I. JACS 1947, 69, 2692.
6. Fish, R. H.; Kuivila, H. G.; Tyminski, I. J. JACS 1967, 89, 5861.
7. Cochran, J. C.; Williams, L. E.; Bronk, B. S.; Calhoun, J. A.; Fassberg, J.; Clark, K. G. OM 1989, 8, 804.
8. Cochran, J. C.; Bronk, B. S.; Terrence, K. M.; Phillips, H. K. TL 1990, 31, 6621.
9. Mitchell, T. N.; Schneider, U. JOM 1991, 405, 195.
10. Amamria, A.; Mitchell, T. N. JOM 1981, 210, C17.
11. Chopa, A. B.; Koll, L. C.; Savini, M. C.; Podestá, J. C.; Newmann, W. P. OM 1985, 4, 1036.
12. Reimann, W.; Kuivila, H. G.; Farah, D.; Apoussidis, T. OM 1987, 6, 557.
13. Mitchell, T. N.; Reimann, W. OM 1986, 5, 1991.
14. Lipshutz, B. H.; Reuter, D. C. TL 1989, 30, 4617.
15. Wickham, G.; Olszowy, H. A.; Kitching, W. JOC 1982, 47, 3788.
16. Ahlbrecht, H.; Weber, P. S 1992, 1018.

William J. Scott & Alessandro F. Moretto

Bayer Pharmaceuticals Division, West Haven, CT, USA



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