Three‐Step Synthesis of 3‐Aryl‐2‐sulfanylthieno[2,3‐ b ]‐, ‐[2,3‐ c ]‐, or ‐[3,2‐ c ]pyridines from the Corresponding Aryl(halopyridinyl)methanones

A convenient three‐step procedure for the synthesis of three types of 3‐aryl‐2‐sulfanylthienopyridines 4, 8 , and 12 has been developed. The first step of the synthesis of thieno[2,3‐ b ]pyridine derivatives 4 is the replacement of the halo with a (sulfanylmethyl)sulfanyl group in aryl(2‐halopyridin‐3‐yl)methanones 1 by successive treatment with Na 2 S⋅9 H 2 O and chloromethyl sulfides to give aryl{2‐[(sulfanylmethyl)sulfanyl]pyridin‐3‐yl}methanones 2 . In the second step, these were treated with LDA (LiN i Pr 2 ) to give 3‐aryl‐2,3‐dihydro‐2‐sulfanylthieno[2,3‐ b ]pyridin‐3‐ols 3 , which were dehydrated in the last step with SOCl 2 in the presence of pyridine to give the desired products. Similarly, thieno[2,3‐ c ]pyridine and thieno[3,2‐ c ]pyridine derivatives, 8 and 12 , respectively, can be prepared from aryl(3‐chloropyridin‐4‐yl)methanones 5 and aryl(4‐chloropyridin‐3‐yl)methanones 9 , respectively.