Facile Preparation of Benzo[4,5]thieno[2,3-b]pyridines and Naphtho[b-4,5]thieno[2,3-b]pyridines via the Reaction of Barton Esters and Benzynes

Titled compounds were prepared in a one-pot synthesis by generating symmetrically substituted benzyne intermediates by the diazotization of anthranilic acids in the presence of Barton esters. Unsymmetrically substituted aryne either gave mixtures of regioisomers or failed. However, nitro and methyl derivatives of titled compounds could be obtained as single products using appropriately substituted Barton esters.