A practical preparation of .alpha.-alkoxylithium reagents: synthesis of syn or anti 1,3-diols

Phenylthio acetals 3 are easily prepared from β-hydroxy aldehydes and can be reduced to anti alkyllithiums 7 and subsequently equilibrated to syn alkyllithiums 9 with excellent stereoselectivity and in good overall yield. A pratical preparation of 3 and a reductive lithiation procedure using catalytic naphtalene makes thse alkyllithium reagents conveniently available on a multigram scale