Selective C-C bond formation from rhodium-catalyzed C-H activation reaction of 2-arylpyridines with 3-aryl-2-azirines.

A novel method for the synthesis of acylmethyl-substituted 2-arylpyridine derivatives using 3-aryl-2-azirines was developed by exploring a prototype reaction using DFT-calculations and carrying out targeted experiments guided by the calculated mechanism. 2-Azirine was initially hypothesized to ring-open at the metal center to furnish familiar metal nitrene complexes that may undergo C-N coupling. Computational studies quickly revealed and prototype experimental work confirmed that neither the formation of the expected metal nitrene complexes nor the C-N coupling were viable. Instead, azirine ring-opening followed by C-C coupling was found to be much more favorable to give imines that readily underwent hydrolysis in aqueous conditions to form acylmethyl-substituted products. This new method was highly versatile and selective toward a wide range of substrates with high functional group tolerance. The utility of the new method is demonstrated by a convenient one-pot synthesis of biologically relevant heterocycles such as pyridoisoindole and pyridoisoqunolinone.