Studies in polypropionate synthesis: High π-face selectivity in syn aldol reactions of tin(II) enolates from (R)-and (S)-1-benzyloxy-2-methylpentan-3-one

Article abstract of DOI:10.1016/S0040-4039(00)74697-1

Use of Sn(OTf)₂/Et₃N in the aldol reactions of the α-chiral ethyl ketones (R)- or (S)-1 with aldehydes leads to high stereoselectivity (90-95% ds, >-97% ee) for the 1,2-syn-2,4-syn adduct 7 or ent-7. This substrate-based selectivity is rationalised by chelation of the Sn(II) enolate.