Three-component and stepwise reactions of salicylic aldehydes (salicylic, 5-bromsalicylic), malononitrile and N-nucleophiles (2-aminopyridines, N-cyanoguanidine) were investigated. 2-Imino-2H-chromene-3-carbonitrile (1) derivatives of various structures are isolated under various conditions.

Reactions of equimolar amounts of salicylic aldehydes, malononitrile and 2-aminopicoline under ultrasound activation conditions in alcohol or aqueous–alcoholic medium in the presence of potassium carbonate or without catalyst led to the formation of 2-iminochromene (1) dimers - 2-amino-6-R-4-((6-R-3-cyano-2H-chromen-2-ylidene)amino)-4H-chromene-3-carbonitriles (2). The subject dimers have been synthesized previously via stirring in methanol and water, in the presence of triethylamine at room temperature for 6-20 h. We observed the formation of these dimers under catalyst-free conditions in higher yield within a shorter reaction time.

Reactions of 2-(2-amino-3-cyano-4H-chromen-4-yl)malononitriles (3) and N-nucleophiles in various solvents under thermal and ultrasound activation conditions did not lead to the expected (pyridin-2-yl)chromeno[3,4-c]pyridinecarbonitriles. However, 2-(4-amino-1-cyano-5-imino-1,3,5,10b-tetrahydro-2H-chromeno[3,4-c]pyridin-2-ylidene)malononitriles (4) were obtained. The novel 2-(4-amino-9-R-1-cyano-5-imino-3,5-dihydro-2H-chromeno[3,4-c]pyridin-2-ylidene)malononitriles (5) were obtained by increasing the reaction time with 2-(2-amino-6-R-3-cyano-4H-chromen-4-yl)malononitriles (3). The structures of the synthesized compounds were established by spectroscopic data (IR, NMR).

The literature describes that the domino-reactions of salicylic aldehydes with one, two, three molecules of malononitrile led to the formation of 2-iminochromene (1) derivatives depending on reaction conditions. However, the authors exclude the formation of dimers during multicomponent reactions of salicylic aldehydes with molecules of malononitrile.

Thus, the isolation of the series of compounds (4), (5), suggests that dimerization and partial hydrolysis reactions of starting nitriles (1) and (3) are more possible to occur, than their interaction with N-nucleophiles.