Effective methods for introducing some aryl and heteroaryl substituent onto 1-azaazulene nuclei

Introduction of aryl and heteroaryl groups onto 1-azaazulene ring was achieved by addition-elimination reaction and Suzuki coupling. Reaction of 2-chloro-1-azaazulenes with 2-aryllithium and 2-heteroaryllithium followed by dehydrogenation with o-chloranil gave 8-aryl- and 8-heteroaryl-2-chloro-1-azaazulene in good yields. Suzuki coupling of 3-iodo-1-azaazulenens with phenylboronic acid in the presence of Pd catalyst afforded 3-phenyl-1-azaazulenes in excellent yield. Suzuki coupling of 2-bromo-1-azaazulenes with phenylboronic acid gave 2-phenyl-1-azaazulenes. Suzuki coupling of 2,3-dibromo-1-azaazulene with phenylboronic acid preferentially occurred at C-2. Reaction of 3-iodo-1-azaazulene with bis(pinacolato)diboron produced 3,3'-bis(1-azaazulene) derivative.