Regio- and Stereoselective Synthesis of Isoindolin-1-ones through BuLi-mediated Iodoaminocyclization of 2-(1-Alkynyl)benzamides.

A simple and straightforward synthesis of isoindolin-l-ones is reported. Exclusive N-cyclization of the amide functional group, an ambident nucleophile, was accomplished for the cyclization of 2-(1-alkynyl)benzamides using n-BuLi-I-2/ICl. The methodology works with the primary amide and affords the desired isoindolinones in yields of 38-94%. Interestingly, the isolated products exhibit a Z-stereochemistry across the C=C double bond. The reaction mechanism involving the formation of either a vinylic anion or an intimate ion pair intermediate is proposed.