Synthesis of spiro(cyclohexa-diene-pyrazolo[1,5-a]pyrimidine-4-ylidene)-malononitrile derivatives

Abstract

The reaction of 4-substituted aryldiazenyl-1 H-pyrazole-3,5-diamines with 7,7′,8,8′-tetra-cyanoquinodimethane gave 2-(2′,7′-diamino-6′-cyano-3′-(aryldiazenyl)-4′ H-spiro(cyclohexa[2,5]-diene-1,5′-pyrazolo[1,5- a]pyrimidine-4-ylidene) malononitriles in 63–79% yield, while, by reaction of 2-aminobenzimidazole with 7,7′,8,8′-tetracyanoquinodimethane, 2-(3′-amino-4′-cyano-6′ H-spiro-(cyclohexa[2′,5′]diene-1,5′-benzo( d)-imidazo[1,2- a]pyrimidine)-4-ylidene)malononitrile was formed in 71% yield. Rationales for these transformations are presented.

Facile and Green Method for the Synthesis of 4-Amino-1,2-Dihydrobenzo [4,5]Imidazo[1,2-a]Pyrimidine-3-Carbonitriles Catalysed by Ammonium Acetate

“…In recent years, several methods have been reported for the synthesis of benzo [4,5]imidazo [1,2-a]pyrimidine derivatives via multi-component condensations of 2-aminobenzimidazole, aldehydes, and malononitrile. [14][15][16] To improve the yields of this three-component condensation reaction, a number of catalysts and techniques, such as microwaves, [17][18][19] MgO, 20 C 5 H 5 N, 21 Et 3 N, [22][23][24] Me 2 NH, 23 and N 2 H 4 , 26 have been used. However, these methods are limited by drawbacks, such as long reaction times, poor yields, harsh reaction conditions or the use of toxic catalysts.…”