Highly Regioselective Synthesis of Substituted Isoindolinones via Ruthenium‐Catalyzed Alkyne Cyclotrimerizations

(Cyclooctadiene)(pentamethylcyclopentadiene)ruthenium chloride [Cp*RuCl(cod)] has been used to catalyze the regioselective cyclization of amide‐tethered diynes with monosubstituted alkynes to give polysubstituted isoindolinones. Notably, the presence of a trimethylsilyl group on the diyne generally led to complete control over the regioselectivity of the alkyne cyclotrimerization. The cyclization reaction worked well in a sustainable non‐chlorinated solvent and was tolerant of moisture. The optimized conditions were effective with a diverse range of alkynes and diynes. The 7‐silylisoindolinone products could be halogenated, protodesilylated or ring opened to access a range of usefully functionalized products.