Microwave‐Assisted Ruthenium‐ and Rhodium‐Catalyzed Couplings of α‐Amino Acid Ester‐Derived Phosphinamides with Alkynes

Abstract

Two different types of new phosphinamide αamino ester derivatives have been prepared in moderate to high yields via ruthenium(II) and rhodium(III)-catalyzed ortho-CÀ H functionalization under microwave irradiation. Specifically, the ortho-alkenylated phosphinamides were produced through coupling of phosphinamides containing an αsubstituted or α,α-disubstituted α-amino ester with internal alkynes under ruthenium catalysis. In contrast, Ru and the more effective Rh-catalyzed coupling of the α-unsubstituted glycine ester phosphinamide with alkynes resulted in formation of oxidative annulation products, phosphaisoquinolin-1-ones. The developed methods feature the use of easily accessible starting materials, short reaction time, exclusive E-stereoselectivity (for ortho-alkenylation) and good functional group tolerance. The alkenylation reaction was readily scaled up to gram scale. Furthermore, the obtained alkenylated phosphinamide could be transformed into Pcontaining dipeptides through hydrolysis of the ester group in the catalysis product and subsequent condensation with an α-amino ester.