Grignard Reagent/CuI/LiCl-Mediated Stereoselective Cascade Addition/Cyclization of Diynes: A Novel Pathway for the Construction of 1-Methyleneindene Derivatives.

Diynes containing a cyclopropane group smoothly undergo a novel intramolecular and stereoselective cascade addition/cyclization reaction to produce the corresponding 1-methyleneindene derivatives in moderate to good yields. This interesting transformation is mediated by Grignard reagent/CuI with LiCl as an additive under mild conditions. The obtained product can easily be further functionalized through cyclopropyl ring opening. A plausible reaction mechanism has also been presented on the basis of deuterium labeling and control experiments. [ABSTRACT FROM AUTHOR]