An unexpected transformation of benzyl carbamates into alpha-azidobenzeneacetamides

Abstract

Successive treatment of benzyl carbamates 5 (Z-protected secondary amines) with lithium diisopropylamide (LDA), diphenyl phosphorochloridate (DPPCl), and NaN3 yielded the corresponding alpha-azidobenzeneacetamides 6 in 45-50% yield (Schemes 2 and 3). In the case of Z-protected diisopropylamine 5b, the phosphate 7 was isolated as a minor product. A reaction mechanism for this unexpected transformation is proposed in Scheme 4, the key step being the ring closure of a benzylic anion to give an oxirane intermediate B. In cursory experiments, it was demonstrated that alpha-azidobenzeneacetamides 6 can be used as 2-phenylglycine synthons in the formation of dipeptides by using a phosphine-mediated coupling (Scheme 5 ) .