Dataset of Regiodivergent Synthesis of Pyrazino-Indolines vs. Triazocines via α-Imino Carbenes Addition to Imidazolidines

Hexahydropyrazinoindoles were prepared in a single step from N-sulfonyl triazoles and imidazolidines. Under dirhodium catalysis, α-imino carbenes were generated and formed nitrogen ylide intermediates that, after subsequent aminal opening, afforded the pyrazinoindoles predominantly via formal [1,2]-Stevens and tandem Friedel-Crafts cyclizations. Of mechanistic importance, a regiodivergent reactivity was engineered through the use of a specific unsymmetrically substituted imidazolidine that promoted the exclusive formation of 8-membered ring 1,3,6-triazocines. Based on first principles, an original Curtin-Hammett-like situation was demonstrated for the mechanism. Further derivatizations lead to functionalized tetrahydropyrazinoindoles in high yields