Interaction of 5-arylfurfurals with malononitrile dimer

Abstract

The interaction of 5-arylfurfurals with dimer malononitrile was studied. A number of previously unknown 3-amino-2,4-dicyano-5-(5-arylfuran-2-yl) -penta-2,4-dienenitriles were obtained, which were investigated in the cyclocondensation reaction with dimedone. The reaction was performed by heating the reagents in ethanol in the presence of piperidine. The reaction was monitored by TLC (eluentbenzene–acetone, 4:1 by volume). It was found that the cyclocondensation reaction proceeds with the formation of pyran and pyridine cycles – fragments of 9-oxa-1-aza-anthracene. The structure of the obtained compounds was confirmed by 1 H NMR spectra. 1 H NMR spectra were recorded on a Bruker instrument with an operating frequency of 400 MHz, solvent – DMSO- d 6 . Chemical shifts are given relative to the solvent signal (DMSO, 2.50 ppm). General procedure of obtaining 3-amino-2,4-dicyano-5-(5-aryl-furan-2-yl)-penta-2,4-dienenitriles ( 1 ). A mixture of 0.003 mol of 5-arylfurfural, 0.003 mol of malonodinitrile dimer and 4 drops of piperidine in 20 ml of ethanol was heated on a boiling water bath until the precipitate dissolved. After cooling, formed precipitate was filtered off and recrystallized from ethanol–DMF (10:1). Synthesis of 2,4-diamino-7,7-dimethyl-5-oxo-10-(5-aryl-furan-2-yl)-6,7,8,10-tetrahydro-5 H -9-oxa-1-aza-anthracene-3-carbonitriles ( 2 ). A mixture of equimolar amounts of substances ( 1 ) and dimedone (0.0014 mol), 0.03 mol of piperidine in 15 ml of ethanol was boiled until complete dissolution of the precipitate. The reaction mixture was cooled, neutralized with concentrated hydrochloric acid. The formed precipitate was filtered off, washed with water and recrystallized from ethanol. Keywords: 5-arylfurfurals, malonodinitrile dimer, dimedone, cyclocondensation reactions, 9-oxa-1-aza-anthracene derivatives.