ON THE ENANTIOSELECTIVE DEPROTONATION SILYLATION OF PROCHIRAL MONOMETHOXYBENZENE-CR(CO)(3) AND 1,2-DIMETHOXYBENZENE-CR(CO)(3) DERIVATIVES

The ortho-deprotonation/silylation of mono- and 1,2-dimethoxy-benzene- Cr(CO)(3) derivatives (5-9) was investigated. The monosilylated produc ts were obtained with high enantioselectivity (up to 96% ee) when the chiral lithium amide 4 was employed as base under in situ quench condi tions. In contrast, the monosilylated benzodioxole-Cr(CO)(3) complex 1 4 was formed with low (< 10 %) ee. The regioselectivity of the formati on of bis(trimethylsilyl)anisole-Cr(CO)(3) as a by-product was shown t o depend on the reaction conditions (kinetic versus thermodynamic cont rol of the deprotonation step).