[4+2]-Cycloaddition of 1,1,3,3-tetramethylguanidine and o-quinone methides: synthesis of arene-fused 2-dimethylamino-4H-1,3-oxazines.

A method for producing substituted 4H-1,3-benzoxazines and their fused derivatives bearing N,N-dimethylamino moiety in the position 2 of 4H-1,3-oxazine ring from phenolic and naphtholic Mannich bases, their iodomethylates or salicylic alcohols, and 1,1,3,3-tetramethylguanidine has been developed. This reaction is supposed to proceed via the generation of o-quinone methides followed by [4+2]-cycloaddition and elimination of dimethylamine. [ABSTRACT FROM AUTHOR]