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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]

The reaction of Mannich bases derived from 2-naphthol with 4-(2-nitrovinyl)morpholine or N,N-di-methyl(2-nitrovinyl)amine in acetic anhydride gives 2-nitro-1H-benzo[f]chromenes. This reaction may be regarded formally as the addition of a push-pull olefin acting as a 1,2-ambiphile with naphthalenic o-quinone methide acting as a 1,4-ambiphilic reagent. [ABSTRACT FROM AUTHOR]

The article focuses on the synthesis of 9,11-diamino-12 H-benzo[5,6]-chromeno[2,3- b]pyridine-10-carbonitriles. The pseudo-three-component reaction apparently proceeds via generation of the o-quinone methide A from the Mannich base, followed by addition of malononitrile by a Michael reaction, intramolecular heterocyclization and condensation of enaminonitrile B formed with a second equivalent of malononitrile, which leads to construction of the pyridine ring.

The article offers information on synthesis of tetrahydro-8 H-chromeno[3,2- h]quinolin-8-ones conducted by the authors. It states that the reaction of the Mannich base with the enamines 2a,b is a tandem process that includes formation of o-quinone methide from the Mannich base. It mentions that infra-red (IR) spectra of compounds 3a,b revealed absorption bands corresponding to the stretching of a carbonyl group.