An unexpected migration of O-silyl group under Mitsunobu reaction conditions

A 1,4 O→O silyl migration followed by nucleophilic substitution with phthalimide was observed under Mitsunobu reaction conditions. This one step secondary alcohol protection and primary alcohol substitution with N-nucleophiles was extended to a variety of 2-hydroxyethyl trialkylsilylether derivatives. A possible mechanism has been postulated based on the pKa values of the alcohol and nucleophile. The present one-pot silyl migration and substitution reaction might find application in the stereoselective synthesis of novel iminosugar derived anti diabetic agents.