Beneficial effect of ortho-methoxy groups in the asymmetric ring opening of meso epoxides with silicon tetrachloride catalyzed by chiral ortho-methoxyphenyldiazaphosphonamide Lewis bases

The reported ability of chiral phosphonamide 1 to effect the enantioselective opening of meso epoxides with silicon tetrachloride has not withstood experimental verification by Denmark's group. Having reexamined the ring-opening of cyclooctene oxide (see scheme), Denmark and co-workers found a serious discrepancy between their results (81-83% recovery of the episode and an essentially racemic product) and those reported by Buono et al. (77% yield and >99% ee).