Asymmetric Ruthenium-Mediated Propargylation of Indoles

Significance

The above reaction with indoles represents an extension of Nishibayashi’s earlier report for the nucleophilic attack of furans and anilines (Synfacts 2007, 1170). Though a number of methods exist for the propargylation of indoles with Brønsted or Lewis acids, none were reported to be asymmetric. The dimeric ruthenium-thiolate complex is prepared in situ and accomplishes the asymmetric Friedel-Crafts-type alkylation to afford 1,1-disubstituted, unprotected propynes in moderate to good yield and good enantioselectivity.