Multilevel selectivity in the mild and high-yielding chlorosilane-induced cleavage of carbamates to isocyanates

The silane-induced cleavage of a series of N-p-tolylcarbamates and N-phenethylcarbamates to isocyanates has been investigated as a function of chlorosilane, carbamate substituent, and reaction conditions. Reaction yields were determined from the isolated ureas, which were formed by trapping the Corresponding isocyanates with isobutylamine. Under room-temperature conditions, multilevel selectivity in carbamate activation has been demonstrated. This selectivity together with the generality of the methodology enhances the utility of carbamates as synthetic intermediates and protecting groups. To demonstrate the effectiveness of this selectivity, a series of biscarbamates were selectively monoactivated to isocyanates in excellent yields.