N-Heterocyclic carbenes of indazole (indazol-3-ylidenes), which are substituted at N1 with aromatics were generated in situ from the corresponding indazolium salts. At 60°C the indazol-3-ylidenes underwent a ring-opening under N-N bond cleavage to intermediary N-(6-methylenecyclohexa-2, 4-dien-1-ylidene) anilines. Trapping of these intermediates by alcohols proved to be a convenient method for the preparation of 2-anilinobenzimidates, which have scarcely been described in the literature. The reaction temperature avoids carbene dimerization, which occurs at -80°C or rearrangement of the ring-opened intermediate to acridines, which affords 100°C. Water converted the ring-opened products into anthranilamides, which were cyclized on reaction with formaldehyde to 2, 3-dihydroquinazolin-4(1H)-ones.
2014 Elsevier Ltd. All rights reserved.