A facile approach for the synthesis of novel substituted 4H-chromenes and condensation reactions of 4H-chromenes leading to chromenopyrrolones and triazolylchromenopyrrolones

A facile method has been developed for the synthesis of 4H-chromene-3-carboxylates 3a-d by the nudeophilic substitution reaction of 2-hydroxy-2H-chromene-3-carboxylates 2a-d with triethylsilane in the presence of BF3 center dot O(C2H5)(2). Cyclocondensation of 4H-chromene-3-carboxylates 3a-d with benzylamines 4a-d afforded a series of 2,3-dihydrochromenopyrrolones 5a-p and with propargylamine afforded 2-propyny1-2,3-dihydrochromenopyrrolones 6a-d. Click reaction of 6a-d with benzyl azides 7a-d provided a series of 1H-1,2,3-triazolylmethyl-2,3-dihydrochromenopyrrolones 8a-p. Thus synthesized compounds 3a-d, 5a-p, 6a-d, and 8a-p are novel heterocyclic compounds and being reported for the first time. (C) 2014 Elsevier Ltd. All rights reserved.