Formation of 3-acylamino-2-arylhydrazono-3-cyano-2,3-dihydro-1H-indoles in the reaction of 2-acylamino-3,3-dichloroacrylonitriles with arylhydrazines

Abstract

The reactions of N-acyl derivatives of 2-amino-3,3-dichloroacrylonitrile with arylhydrazines are used successfully for the synthesis of functionally substituted heterocyclic compounds [1][2][3]. Thus, with phenylhydrazine in tetrahydrofuran, compounds 1a-c give 4-cyano-2-methyl(aryl)-5-(2-phenylhydrazino)-1,3-oxazoles 2a-c, while 2-methoxycarbonylamino-3,3-dichloroacrylonitrile (1d) under the same conditions forms 5-amino-4-methoxycarbonylamino-1-phenyl-3-phenylazopyrazole (3) [1,2]. At the same time, compound 1d in reaction with arylhydrazines in methanol in the presence of triethylamine gives the substituted triazolones 4a,b [3]. The different direction of the cyclization in the reagents 1a-d is presumably due to the steric effects created by the methoxycarbonyl group and also to the decrease in the mobility of the proton in the MeOCONH fragment compared with the acetyl and aroylamino groups.All the reactions described above were conducted at room temperature. The aim of the present work was to study the reaction of 2-acylamino-3,3-dichloroacrylonitriles 1a-d with arylhydrazines at elevated temperature, in order to determine the temperature effect on the direction of the reactions and on the structure of the products. It was found that the reaction products are oxazole or indole derivatives, depending on the structure of the starting acrylonitriles 1a-d.

Reactions of New N-(2,2-Dichloro-1-cyanoethenyl)amides with Aliphatic Amines

“…Previously, we have shown that substituted 2-acylamino-3,3-dichloroacrylonitriles can be used to produce various heterocycles such as thiophene [1], hydantoin [2], and indole derivatives [3]. However, most reactions of 2-acylamino-3,3-dichloroacrylonitriles with amines provide oxazole derivatives [4][5][6].…”