Palladium-catalyzed, microwave-assisted synthesis of 3,4-dihydro-3-oxo-2 H -1,4-benzoxazines: An improved catalytic system and multicomponent process

摘要

An improved palladium-catalyzed system is established for the synthesis of 3,4-dihydro-3-oxo-2H-1,4-benzoxazines from less reactive ethyl 2-(2-chlorophenoxy)alkanoates and aryl amines under controlled microwave heating, employing 2-dicyclohexylphosphino-2′,4′,6′- triisopropylbiphenyl (XPhos) as the ligand. Moreover, a high-yielding, three-component reaction protocol is disclosed for the efficient one-pot synthesis of 3,4-dihydro-3-oxo-2H-1,4-benzoxazines from 2-halophenols, ethyl 2-bromoalkanoates, and aryl amines. Microwave heating at high temperature is necessary to achieve high yields with 2-chlorophenol. A wide range of substrates is tolerated affording the desired products in good to excellent yields.