Synthesis of 2,7-Methano-aza[10]annulene Derivatives

Electrocyclic ring-closure of 6-vinylcyclohepta-1,3,5-isocyanate has been carried out in the presence of triphenylphosphine to examine a catalyzing effect of the triphenylphosphine. The preparation of 10-(1-carboalkoxyalkyl)-2,7-methanoaza[10]annulenes by the electrocyclic ring-closure of ketenimine intermediates, which are formed by the reaction of triphenylalkylidenephosphorane and 6-vinylcyclo-hepta-1,3,5-isocyanate, is described. 10-Alkyl-2,7-methanoaza[10]annulenes were prepared by basic hydrolysis of the carboalkoxyaza[10]annulenes and decarboxylation of the acid intermediates. In the same manner, 10-(N-alkyl(or aryl))-2,7-methanoaza[10]annulenes were prepared from the reaction of the isocyanate and N-alkyl(or aryl)iminotriphenylphosphorane via electrocylic ring-closure of carbodiimide intermediate.