Proline-catalyzed facile access to Mannich adducts using unsubstituted azoles

A novel and facile method for the direct construction of C–C–N bond with unsubstituted azoles under Mannich conditions is developed for the first time. The reaction is catalyzed efficiently by l-proline to give the Mannich adducts 1a–10b in DMSO, whereas in water, insertion of two successive bonds, C–C–N and C–C–O occurred to give compounds 11a–20b. The latter are deformylated readily into the desired products 1a–10b under basic conditions. Mechanistic aspects for the formation of these products are discussed.