FeCl₃-Catalyzed Intramolecular Hydroarylation of Alkynes

Abstract

The intramolecular hydroarylation of alkynes using a substoichiometric amount of FeCl₃ is described. When starting from tetrasubstituted substrates, products resulting from an unexpected toluene (or xylene) elimination are isolated in good yields.

Key words

electrophilic aromatic substitutions - arylations - iron - ring closure

References and Notes

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9

As pointed out by a referee, the lack of reactivity in compound 2e can also be explained by some poisoning effect of the nitro group which kills the Lewis acidity of FeCl₃.

11

General Procedure: To a solution of alkyne (0.2 mmol) in 1,2-dichloroethane (8 mL) under nitrogen was added iron(III) chloride hexahydrate (0.02 mmol, finely ground). The mixture was then stirred at r.t. until completion of the reaction (TLC monitoring). The mixture was concentrated under vacuum and the crude material was loaded onto a silica gel column and chromatographed with heptane to give the cyclization product.