Lithium enolates, 1,2-silicon shift

Murai and coworkers reported on operationally simple aldol reactions with lithium enolates generated from carbonylation of silylmethyl lithium species [57]. Upon 1,2-silicon shift, a-silyl acyllithium species can be stereo-selectively converted to (E) lithium enolates that undergo addition to aldehydes to give /3-hydroxy acylsilanes (Scheme 14). 

Scheme 14 1,2-Silicon shift toward lithium enolates...

A further efficient preparation of these silyl enol ethers proceeds through an intramolecular 1,2-silicon shift in an a-silyl acyl lithium substrate (8), prepared from an a-lithiosilane (Scheme 23)". This method appears very simple to carry out, and produces the silyl enol ethers in good yields with high isomeric purity (usually, E isomer > 90% of mixture). 

Acylsilanes. Carbonylation of trimethylsilylmethyllithium (1) in ether at 15° followed by quenching with ClSilCH,), results in the trimethylsilyl enolate (2) of acetotri-methylsilane. The reaction evidently involves insertion of CO to give an acyllithium (a), which undergoes a 1,2-silicon shift to give the lithium enolate (b) of an acylsilane. 

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