1H-Isoindolynes: Arynes Accessible by a One-Pot, Ambient Temperature, Three-Component Cascade

We describe here a new type of aryne: 1H-isoindolynes. These can be accessed by variants of a process in which a primary propargylic diynol, a propargylic aminodiyne, and an aryne-trapping agent are treated with an oxidizing agent capable of producing, in situ, a 2,4-diynal. This mixture undergoes a room temperature cascade of events involving imine condensation, imine E-to-Z isomerization, hexadehydro-Diels−Alder cycloisomerization, and a final aryne-trapping reaction. This convergent strategy gives isoindolyne adducts in good to excellent yields. Insights into subtle aspects of the mechanism were gained by examining the reaction by 1H NMR spectroscopy, through control reactions involving isolable iminotriynes, and using density functional theory calculations.