Iridium-Catalyzed [2 + 2 + 2] Cycloaddition of Bithiophen-Linked Diynes with Nitriles: Scope and Mechanistic Study with Quantum Chemical Calculation.

We report a simple and atom-efficient method for the synthesis of bithiophene-fused isoquinolines by iridium-catalyzed [2 + 2 + 2] cycloaddition of bithiophene-linked diynes with nitriles. All three structural isomers of bithiophene-linked diynes underwent [2 + 2 + 2] cycloaddition, and the trend in the reactivity for cycloaddition was diyne = diyne > diyne . Dibenzothiophene-linked diyne also reacted with nitriles to form a variety of cycloadducts.