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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 discusses the scientific method for the synthesis of 1,5-dihydro-2H-chromeno[2,3-d]pyrimidine-2,4(3H)-diones from o-benzoquionone methide precursors including quaternary ammonium salt, mannich base and hydroxybenzyl alcohols. The chemical reactions of methide precursors were out by refluxing an equimolar mixture of reagents into an acetic acid. It conclude that advantages for developing method for preparing 2H-chromeno[2,3-d]pyrimidinediones uses o-benzoquionone methide precursors.

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.

The article discusses about a new approach to synthesize benzo[e]pyrazolo[5,1-b][1,3]oxazines which involves heating 3,4, 5-tribromopyrazole with salicylic alcohols in dimethylformamide (DMF) at reflux in presence of sodium carbonate. It informs that Pyrazolylmethylphenols are formed in the absence of potassium carbonate. In the synthesis reactions the alkylating agents are o-methylenequinones formed during dehydration of the salicyl alcohols.