SELECTIVE TRANSFORMATION OF O-2-(TRIMETHYLSILYL)ETHYL AND O-TERT-BUTYL CARBAMATES INTO O-BENZYL CARBAMATES USING BENZYL TRICHLOROACETIMIDATE

We recently attempted to benzylate the hydroxyl group of the bulgecinine derivative (l)1with benzyl trichloroacetimidate (2) in the presence of a catalytic amount of trifluoromethanesulfonic acid.2 Upon workup, the expected benzyl ether (3) was isolated (50%) along with the O-benzyl carbamate benzyl ether (4) (20%). To our knowledge, the direct conversion of an O-alkyl carbamate into an O-benzyl carbamate (Cbz) (1 to 4) has not been described. However, a two-step procedure for converting O-tert-butyl carbamates (BOC) into O-benzyl carbamates via the O-tert-butyldimethylsilyl carbamate has been reported by Ohfune and co-workers.3 The reactive O-tert-butyldimethylsilyl carbamate intermediate is also. © 1990, American Chemical Society. All rights reserved.