Partially fluorinated heterocyclic compounds. Part XI. The reactions of lithium pentafluorobenzenethiolate with acetylenic compounds giving benzo[b]thiophen derivatives and/or olefins

Abstract

Lithium pentafluorobenzenethiolate reacts (i) with diethyl acetylenedicarboxylate to give diethyl 4,5,6,7-tetrafluorobenzo[b]thiophen-2,3-dicarboxylate; (ii) with ethyl phenylpropiolate to give ethyl 4,5,6,7-tetrafluoro-2-phenylbenzo[b]thiophen-3-carboxylate and a small amount of the product of thiol addition to the triple bond; (iii) with hexafluorobut-2-yne to give 4,5,6,7-tetrafluoro-2,3-bistrifluoromethylbenzo[b]thiophen and the all-trans-1-pentafluorophenylthio-1,2,3,4-tetrakistrifluoromethylbutadiene; (iv) with ethyl propiolate to give ethyl cis- and trans-β-(pentafluorophenylthio)acrylate; and (v) with diphenylacetylene to give cis- and trans-α-pentafluorophenylthiostilbene. The failure to trap olefinic material in (i), and the absence of cyclised materials in (iv) and (v) have not been rationalised.