The Condensation of Salicylaldehydes and Malononitrile Revisited:  Synthesis of New Dimeric Chromene Derivatives

Abstract

The reaction of salicylic aldehydes with malononitrile was reinvestigated, and the reaction pathway was followed by 1H NMR spectroscopy. A delicate control of the experimental conditions allowed the synthesis of 2-imino-2H-chromene-3-carbonitriles 1, (2-amino-3-cyano-4H-chromen-4-yl)malononitriles 2, 4-amino-5-imino-2,7-dimethoxy-5H-chromeno[3,4-c]pyridine-1-carbonitrile 12, and (4,5-diamino-1-cyano-1,10b-dihydro-2H-chromeno[3,4-c]pyridin-2-ylidene)malononitrile 13. Two novel 2-iminochromene dimers, with structures 8 and 9, were isolated and fully characterized. The activity of compound 8a on Aspergillus spp. growth and on ochratoxin A production was evaluated. The results of the bioassays indicate that compound 8a, applied at concentrations of 2 mM, totally inhibited the growth of the fungi tested. Ochratoxin A production by Aspergillus alliaceus was reduced by about 93% with a 200 microM solution of this compound. A moderate inhibitory effect was observed for the analogous structure 8b, and no inhibition was registered for compounds 2 and 1, used as synthetic precursors of the dimeric species 8.

Highly Efficient Synthesis of New 2H-Chromene Dyes using Cu-SBA-15

“…Until now, diverse methods have been published for the synthesis of 2H-benzopyran derivatives [11][12][13][14][15][16][17] . They are also good intermediates that have been applied in several organic synthesis [18][19][20] .…”

A cost-effective and green aqueous synthesis of 3-substituted coumarins catalyzed by potassium phthalimide

“…In addition to this, the 3-substituted coumarins are also prepared by the Knoevenagel condensation of salicylaldehydes with compounds containing active methylene group including Meldrum's acid, maleic acid, malonic acid, malonate esters, malononitrile, or ethyl cyanoacetate [19]. This reaction can be catalyzed by various catalysts such as mesoporous molecular sieve MCM-41 [20] [22], L-proline [23], piperidine [24], ZrCl 4 in ionic liquid [25], natural clay [26], Mg-Al hydrotalcite [27], NaOH [28], basic alumina followed by grinding with ptoluenesulphonic acid [29], Na 2 CO 3 and NaHCO 3 [30]. 3-Substituted coumarins can be obtained under phase-transfer catalyzed conditions [31].…”

Synthesis and in vitro antimicrobial evaluation of penta-substituted pyridine derivatives bearing the quinoline nucleus

“…Among them, 2-amino-3-cyanopyridine derivatives are well known for their versatile biological activities like antimicrobial (Mahmoud et al, 2007;Mungra et al, 2009), antifungal (Costa et al, 2008), isoniazid derivatives bearing the pyridine nucleus possess anti-tubercular (Ashrafali et al, 2010;Lourenco et al, 2007) and some of 3-cyano-2-pyridone derivatives having anti-inflammatory activity (Amr and Abdulla, 2006). Moreover, the polysubstituted pyridine represents molecular framework that serve as a platform for development of pharmaceutical agents.…”