Gold-catalyzed cycloisomerization of alk-4-yn-1-ones.

Volker Belting, Norbert Krause

Dortmund University of Technology, Organic Chemistry, Otto-Hahn-Strasse 6, D-44227, Dortmund, Germany.

Organic & biomolecular chemistry 2009 Mar 21

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Depending on the substitution pattern and the solvent, the gold-catalyzed cyclization of alk-4-yn-1-ones affords different oxygen heterocycles under mild reaction conditions. Alkynones with one substituent at C-3 undergo a 5-exo-dig cycloisomerization to substituted furans , whereas a 6-endo-dig cyclization to 4H-pyrans is observed with substrates bearing two substituents at C-3. In alcoholic solvents, alkylidene/benzylidene-substituted tetrahydrofuranyl ethers are formed in a tandem nucleophilic addition/cycloisomerization.