Electrophilic Cyclisation of Bis(4-methoxybenzylthio)acetylene − Competition Between Ar2-6 and Ar1-5 Routes, Yielding 1H-2-Benzothiopyrans or Spiro Derivatives of Cyclohexadienone
作者:Thomas R. Appel、Nasser A. M. Yehia、Ute Baumeister、Helmut Hartung、Ralph Kluge、Dieter Ströhl、Egon Fanghänel
(Ar1-5 route). The fate of the ipso σ complex is determined by the presence or absence of nucleophiles in the reaction medium. When nucleophiles are excluded, the σ complex is stabilised by 1,2-migration and formation of 1H-2-benzothiopyran 2a. In the presence of water, the σ complex yields spirocyclohexadienone dihydrothiophenes 3a and 3d. In the presence of 3-methylbenzyl alcohol, the methoxy substituent