Furopyridines. XII. Reaction of 3‐bromo, 2‐phenylthio and 2‐phenylthio‐3‐bromo derivatives of furo[2,3‐b]‐, furo[3,2‐b]‐, furo[2,3‐c]‐ and furo[3,2‐c]pyridine with several alkyllithiums

This paper describes reactions of 3‐bromo‐ 1a‐d, 2‐phenylthio‐ 5a‐d and 2‐phenylthio‐3‐bromofuropyridines 6a‐d with n‐butyl‐, t‐butyl‐ and methyllithium and lithioacetonitrile. Lithiation of compounds 1a‐d with n‐butyl‐ or methyllithium gave the parent furopyridines 2a‐d and o‐ethynylpyridinols 3a‐d. Reaction of compounds 5a‐d with methyllithium afforded o‐(phenylthioethynyl)pyridinols 7a‐d, which were also yielded by reaction of compounds 6a‐d with t‐butyl‐ or methyllithium. The phenylthio group in compounds 7a‐d were substituted with t‐butyl group by the reaction with excess t‐butyllithium. In contrast, 2‐phenylthio group in compounds 5a‐d and 6a‐d was substituted with cyanomethyl group by reaction with lithioacetonitrile to give compounds 11a‐d and 10b, c respectively.