An Efficient Synthesis of 1-Arylbenzo[c]thiophenes via the Reaction of 2-(Chloromethyl)phenyllithiums with Aromatic Aldehydes

A simple and efficient sequence for the preparation of 1-arylbenzo[c]thiophenes has been developed.Thus, 2-(chloromethyl)phenyllithiums, generated by treating 2-(chloromethyl)phenyl bromides with butyllithium, are allowed to react with aromatic aldehydes to afford the corresponding diarylmethanol derivatives.These alcohols are oxidized with pyridinium chlorochromate (PCC) to give aryl[(2-chloromethyl)phenyl]methanones, of which treatment with sodium hydrogensulfide gives 1-aryl-1,3dihydrobenzo[c]thiophen-1-ols.Dehydration of these crude alcohols to the desired products can be accomplished by the treatment with a catalytic amount of p-toluenesulfonic acid.