Vasicine from Adhatoda vasica as an organocatalyst for metal-free Henry reaction and reductive heterocyclization of o-nitroacylbenzenes

Abstract

Vasicine, a quinazoline alkaloid, from the leaves of Adhatoda vasica, has been utilized as an efficient catalyst for metal and base free Henry reaction of various aldehydes with nitro alkanes. The method can be used in the synthesis of various β-nitro alcohols under mild reaction conditions without use of hazardous organic solvents and expensive catalysts. Vasicine is also applied successfully for one pot synthesis of 2,1-benzisoxazoles from o-nitroacylbenzenes in good yields under mild conditions.