Substituent effect on anionic cycloaromatization of 2-(2-substituted ethynyl)benzonitriles and related molecules

Mothanolysis of 2-(2-substituted ethynyl)benzonitriles based on the nature of substituents gave 5-exo product, isoindolones and 6-endo product, isoquinolones, respectively. When a bulky substituent, such as tert-butyl group, was employed in this cyclization reaction, a 5-exo adduct was obtained. Phenyl and thienyl groups which can stabilize the alpha-anion affect the cyclization reaction to produce the 5-exo adducts. Pyridinyl and pyrazinyl groups can also stabilize the a-anion, but the formation of a more stable intermediate by coordination of sodium with nitrogen atom leads to the 6-endo products. (C) 2002 Elsevier Science Ltd. All rights reserved.