Iron(III) Chloride and Diorganyl Diselenide‐Promoted Nucleophilic Closures of 1‐Benzyl‐2‐alkynylbenzenes in the Preparation of 9‐(Organoselanyl)‐5H‐benzo[7]annulenes

Iron‐promoted cyclization of 1‐benzyl‐2‐alkynylbenzenes with diorganyl diselenides led to the synthesis of 9‐(organoselanyl)‐5 H ‐benzo[7]annulenes whereby the mutual action between diorganyl diselenides and iron(III) chloride in a 0.5:1.0 mol ratio was essential in order to achieve the maximal yields of the products. The cyclization reaction tolerated a variety of functional groups, such as trifluoromethyl, chloro, fluoro and methoxy, in both the 1‐benzyl‐2‐alkynylbenzenes and the diorganyl diselenides, giving the seven‐membered heterocyclic products exclusively via a 7‐ endo ‐ dig cyclization process. magnified image