Regioselective Synthesis of Acylated N-Heterocycles via the Cascade Reactions of Saturated Cyclic Amines with 2-Oxo-2-arylacetic Acids.

A highly regioselective and versatile synthesis of acylated N-heterocycles from the cascade reactions of saturated cyclic amines with 2-oxo-2-arylacetic acids is presented. Mechanistically, the formation of the title compounds involves first a C(sp3)-H bond dehydrogenation of cyclic amine to give an enamine intermediate followed by its cross coupling with the acyl species in situ generated through the decarboxylation of 2-oxo-2-arylacetic acid. Interestingly, in this cascade process, the copper catalyst is believed to play a crucial role not only in dehydrogenation but also in the decarboxylation and cross coupling reaction. To the best of our knowledge, this is the first example in which different classes of acylated N-heterocycles were directly prepared from the readily available saturated cyclic amines by using 2-oxo-2-arylacetic acids as the noncorrosive and easy to handle acylating reagents. Compared with literature methods, this new protocol has the advantages such as readily obtainable substrates, broad substrate scope, high efficiency, and good selectivity.