Base-Induced Highly Regioselective Synthesis of N2-Substituted 1,2,3-Triazoles under Mild Conditions in Air

We developed a highly regioselective base-induced synthesis of N²-substituted 1,2,3-triazoles from N-sulfonyl-1,2,3-triazoles and alkyl bromides/alkyl iodides at room temperature. We propose an S_N2-like mechanistic pathway to explain the high N²-regioselectivity. The protocol features a broad substrate scope and generates products in good to excellent yields (72-90%).

Doyle-Kirmse reaction using 3,3-difluoroallyl sulfide and N-sulfonyl-1,2,3-triazole: an efficient access to gem-difluoroallylated multifunctional quaternary carbon

A Doyle-Kirmse reaction of N-sulfonyl-1,2,3-triazole with 3,3-difluoroallyl sulfide through a Rh(ii)-catalyzed [2,3]-sigmatropic rearrangement has been developed, which provides an efficient access to multifunctional quaternary centers containing aryl, imino, thio, and brominated gem-difluoroallyl groups. The reaction features broad substrate scope with moderate to excellent yields. The applicability of the method is confirmed by gram-scale synthesis and further transformations.

Rh(ii)-Catalyzed denitrogenative 1-sulfonyl-1,2,3-triazole-1-alkyl-1,2,3-triazole cross-coupling as a route to 3-sulfonamido-1H-pyrroles and 1,2,3-triazol-3-ium ylides

The reaction of 1-alkyl-1H-1,2,3-triazoles with rhodium(ii) azavinyl carbenes, generated from 1-sulfonyl-1H-1,2,3-triazoles, was utilized to prepare 3-sulfonamido-1H-pyrroles and 1,2,3-triazol-3-ium ylides in good yields.

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 DFT calculations, an original Curtin–Hammett-like situation was demonstrated for the mechanism. Further derivatizations led to functionalized tetrahydropyrazinoindoles in high yields.

Hexahydropyrazinoindoles are prepared in a single step from N-sulfonyl triazoles and imidazolidines. Of mechanistic importance, a regiodivergent reactivity can be engineered towards the exclusive formation of 8-membered ring 1,3,6-triazocines.

Synthesis of α-cyano sulfone via thermal rearrangement of 1,4-disubstituted triazole mediated by carbene and radical species

α-Cyano sulfone is produced conveniently from 1,4-disubstituted triazole, which involves carbene, ketenimine and radical species as the key intermediates.