Cyclobutarenes. Part 2. Azaquinomethanes as reactive intermediates: synthesis of cyclobuta[b]pyridine and cyclobuta[b]pyrazine derivatives

Cyclisation of 2,3-bis(dibromomethyl)pyridine (1) and 2,3-bis(dibromomethyl)pyrazine (3) with sodium iodide gives the dibromodihydrocyclobutarenes (10) and (13). The intermediate quinomethanes (6) and (7), together with the pyrimidine and 1,2,4-triazine analogues (8) and (9), are readily trapped via cycloaddition reactions.