Intramolecular Cyclization of the ortho-Substituted N-arylquinone Imines under Basic and Thermal Conditions

The S(O,N)-benzyl ethers of N-arylquinone imines undergo cyclization under the action of bases to form products of the benzothiazol, benzoxazole, and benzimidazole series, while under thermal conditions they undergo a non-catalyzed rearrangement to form spiro-cyclohexadiene derivatives of benzazines. The benzimidazole, spirobenzothiazine, and spirobenzoxazine structures were supported by the x-ray diffraction method. The possibility of intramolecular photochemical cyclization was investigated; ortho-S(O,N)-benzyl-substituted N-arylquinone imines show high photostability under UV irradiation. The features of the cyclization processes of quinone imine derivatives were revealed by DFT calculations using the wB97XD/6-311++G** method.