Isoxazole as a nitrile synthon: en routes to the ortho-alkenylated isoxazole and benzonitrile with allyl sulfone catalyzed by Ru(ii)

Abstract

A Ru(II) catalyzed regioselective Heck-type C–H olefination of isoxazole with unactivated allyl phenyl sulfone is revealed. The solvent DCM offers dual sp²–sp² C–H activation via an N-directed strategy, leading to ortho-olefinated isoxazoles with exclusive E-selectivity. On the other hand, in DCE solvent, isoxazole serves as the nitrile synthon and leads to o-olefinated benzonitrile. At a higher temperature (110 °C) in DCE, after the ortho-olefination Ru(II) mediated cleavage of isoxazoles delivered the nitrile functionality.