Tributylstannyllithium

The addition of tributylstannyllithium to the carbonyl group of various a-substituted aldehydes is accompanied by asymmetric a-induction8. The extent depends only on the relative sizes of a-substituents. The tributylstannyl anion exhibits much the same stereoselectivity as unhindered Grignard reagents (for 2,3-dimethylbutanal d.r. 3 1 and 2.5 1, respectively). Stereoselectivity is improved with aldehydes substituted at the /(-position by oxygen. For example, when a-methyl-/i-(benzyloxy)methoxypropanal is treated with tributylstannyllithium in tetrahydrofuran, a mixture of diastereomers is formed, the ratio of which varies from 5 1 at — 78°C to8 l at — 119"C8. 

Aldehydes and a-bromo ketones or esters are efficiently coupled in an aldol reaction in the presence of Diethylalu-minum Chloride-Tributylstannyllithium (or Tin(II) Chloride)... 

Li, and NMR spectra of three species detected in solutions of tributylstannyllithium in diethyl ether that were titrated with HMPA at low temperatures. Adapted with permission from [32]. Copyright 1994 American Chemical Society. 

Preparative Methods most conveniently prepared by reacting tributylstannyllithium with commercially available 2-chloromethyl-3-trimethylsilyl-l-propene, although methods involving reaction of the dithiocarbamate or allylic sulfide derived from 2-trimethylsilylmethylprop-2-en-ol with BusSnH and AIBN have been reported. ... 

Reduction of a-silyl sulfides with tributylstannyllithium is also useful for the generation of a-silyl carbanions [251]. When a,a-bis(trimethylsilyl)alkyl phenyl sulfides 137 are treated sequentially with tributylstannyllithium and aldehydes, they give the corresponding alkenylsilanes (Scheme 2.87). This method has an advantage in that tributylstannyllithium is thermally stable and can be stored for several months. 

Scheme 2.87. The Peterson reaction of a-silyl carbanions generated by reduction of a sulfanyl group with tributylstannyllithium.

Marshall s optically active stannanes are readily prepared by the addition of tributylstannyllithium to crotonaldehyde (158), oxidation of the ensuing alcohol to the acyl stannane (159), and enantioselective reduction with Noyori s BINAL-H [110] (Scheme 5.27) [107]. Protection of the secondary alcohol furnishes a-alkoxy-substituted allylstannane 160 that partakes in the stereo-specific rearrangement to afford 161 in 80% yield. 

---