The Craven reaction with 2-aryl-1,4-benzoquinones

Abstract

It is known that the interaction of 1,4-quinones with 1,3-dicarbonyl compounds mainly results in the formation of benzo[ b ]furan derivatives, which attract special attention because many compounds of this class are biologically active and are used as drugs. However, in some cases, this interaction is ambiguous, and along with the main reaction products – substituted benzofurans, significant amounts of benzodifurans are formed. Cyanoacetic acid derivatives are particularly prone to react with 1,4-quinones to form benzodifurans. In particular, the addition of compounds with an active methylene group to quinones takes place with the formation of colored intermediates and is known in the literature as the Craven reaction. On the other hand, benzodifurans are widely used in the bioorganic and medical fields, as building blocks for optoelectronic devices, organic dyes for solar panels, components in the manufacture of organic LEDs, as well as polymeric materials with a rigid structure such as Kevlar. Possibility of preparation of linear heterocyclic systems arylfuro[2’,3’:4,5]benzo[ b ]-furanes based on 2-aryl-1,4-benzoquinones was investigated. The 2-aryl-1,4-benzoquinones 1 а – і (аryl = 4-MeC 6 H 4 ( a ), 2-C 10 H 7 ( b ), 3-CF 3 C 6 H 4 ( c ), 4-COMeC 6 H 4 ( d ), 4-NHCOMeC 6 H 4 ( e ), 3-NO 2 C 6 H 4 ( f ), 3,4-Me 2 C 6 H 3 ( g ), 3-Cl-4-MeC 6 H 3 ( h ), 3,4-Cl 2 C 6 H 3 ( i )) were obtained by the reaction between arenediazonium salts and 1,4-benzoquinone under Meerwein reactions conditions. The interaction of 2-aryl-1,4-benzoquinones 1a – i with some bifunctional C-nucleophiles under the conditions of the Craven reaction was studied. It was found that esters of cyanoacetic acid (ethyl-, propyl-, allylcyanoacetates) and malononitrile react selectively with arylquinones – substituted furobenzo[ b ]furanеs 2a – с , 3a – с , 4 , 5a – e were obtained in a medium yields. The structures of the synthesized compounds were confirmed by the 1 H NMR spectroscopy and element analysis data. Keywords: 2-aryl-1,4-benzoquinones, cyanoacetic esters, malononitrile, Craven reaction, arylfuro[2’,3’:4,5]benzo[ b ]furanes.