The ability of 3-arylmethylene-3H-furan-2-ones to take part in Michael condensation as acceptors was used earlier in the reaction with cyclohexanone [1], acetylacetone [2], and acetoacetic ester [3].In a continuation of investigations into the reactivity of 3-arylmethylene-3H-furan-2-ones with methylene-active compounds their behavior in reaction with malononitrile was studied.The presence of the highly reactive methylene and cyano groups in malononitrile makes it possible to use this compound as a reagent for cyclizations leading to the formation of carbo-and heterocyclic compounds.The reaction of 5-aryl-3-arylmethylene-3H-furan-2-ones 1-4 with malononitrile was realized by heating the reagents in solution in DMSO in a molar ratio of 1:1 in the presence of catalytic amounts of triethylamine.
1-4 5-8Et 3 N 1, 5 R = C 5 H 11 ; 2, 6 R = Ph; 3, 7 R = p-Tol; 4, 8 R = 3-MeOC 6 H 4
Keywords:6-amino-4-aryl-2-R-4H-furo[2,3-b]pyran-5-carbonitriles, 4-aryl-6-ethoxy-2-R-furo-[2,3-b]pyridine-5-carbonitriles, ethyl acetoacetate, ethyl esters of 5-amino-4-aryl-7-methyl-2-R-4H-1,9-dioxa-8-aza-cyclopenta[b]naphthalene-6-carboxylic acids, recyclization.6-Amino-4-aryl-2-R-4H-furo[2,3-b]pyran-5-carbonitriles 1-3 are an important class of heterocyclic compounds, which hold considerable interest in light of their various chemical transformations and practical applications [1]. These bifunctional compounds, containing vicinal nitrile and amino groups, are promising starting materials for obtaining previously not readily available fused heterocyclic systems. The synthesis of carbonitriles 1-3 employs the base-catalyzed Michael condensation of 5-aryl-3-arylmethylene-3H-furan-2-ones with malononitrile [2].The reaction of carbonitriles 1-3 with a C-nucleophile, namely, ethyl acetoacetate, upon heating in ethanol at reflux in the presence of catalytic amounts of triethylamine gives ethyl esters of 5-amino-4-aryl-7-methyl-2-R-4H-1,9-dioxa-8-azacyclopenta[b]naphthalene-6-carboxylic acids 4-6. O O Ar NH 2 R CN Me O O EtO Et 3 N O N O R Ar NH 2Me CO 2 Et 4-6 1-3 + 1, 4 R = Ph; 2, 5 R = 4-MeC 6 H 4 , 3, 6 R = 4-MeOC 6 H 4 ; 1-6 Ar = 2-ClC 6 H 4
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