Chiral Acylsilanes in Organic Synthesis. Diastereoselective 1,2‐Additions to Racemic Alkoxymethyl‐Substituted Acylsilanes

The synthesis of the three alkoxymethyl‐substituted acyisilanes 1–3 is described (Schemes 1 and 2). Their reactions with NaBH4 as well as PhLi gave the corresponding alcohols with moderate to good diastereoisomeric induction (up to 78% de; see Table), depending upon the solvent used (Scheme 3). The results indicate that in Et2O, the reactions with PhLi proceed via 6‐membered chelates (see C in Scheme 4) leading to the products with high de's (74–78%). In THF, these chelates are not formed, and as a consequence, the additions take place with reversed and lower stereoselectivities (34–50% de).