Cyano esters and malononitriles. V. Cyano(fluorenyl)acetic esters, hydroxy nitriles and benzimidazolylacetonitriles

Abstract

In contrast to the analogous ylidenemalononitriles, it is found that xanthen-, thioxanthen- and fluoren-9-ylidene cyanoacetates react with organomagnesium halides to give 1,4-adducts regardless of the nature of the Grignard reagent and its steric requirements. Apparently the reaction proceeds through the intermediate formation of a cyclic transition state of lower energy in the case of cyano esters than in the case of malononitriles.     The fluorenyl cyano esters (2b-e,g) react with o-phenylenediamine at 240° affording the benz-imidazolyl(fluorenyl)acetonitriles (10a-e), whereas, at lower temperature, the intermediate cyano anilides (11a-e) are obtained which cyclize readily to the corresponding benzimidazoles.