An efficient, Rh(II)-catalyzed, denitrogenative reaction of 4-vinyl benzoxazinanones with N-sulfonyl-1,2,3triazoles has been developed for the synthesis of structurally diverse tricyclic 2-imidazolones in moderate to good yields with excellent diastereoselectivities. The reaction consists of the sequential formation of four new bonds: two C−N and two C−O bonds in a cascade fashion. The reaction works under operationally simple conditions and also represents the first catalytic nondecarboxylative cyclization of vinyl benzoxazinanones with triazoles.

Herein, we present a substrate-controlled regiodivergent strategy for the selective synthesis of C3 or C2-alkynylated indoles via ruthenium-catalyzed [3 + 2]-annulation of readily available pyrazolidinones and 1,3-diynes. Remarkably, C3-alkynylated indoles were obtained in good yields when 1,4-diarylbuta-1,3diynes were employed as the coupling partners. On the other hand, dialkyl-1,3-diynes led to the selective formation of C2-alkynylated indoles. The key features of the strategy are the operationally simple conditions and external-oxidant-free, broad-scope, and substrate-switchable indole synthesis. Scale-up reactions and further transformations expanded the synthetic utility of the protocol.

A metal- and additive-free, highly efficient, step-economical deoxygenative C2-heteroarylation of quinolines and isoquinolines was achieved from readily available N-oxides and N-sulfonyl-1,2,3-triazoles. A variety of α-triazolylquinoline derivatives were synthesized with good regioselectivity and in excellent yields under mild reaction conditions. Further, a gram-scale and one-pot synthesis illustrated the efficacy and simplicity of the developed protocol. The current transformation was also found to be compatible for the late-stage modification of natural products.

A rhodium-catalyzed intramolecular denitrogenative transannulation of N-sulfonyl-1,2,3-triazole-tethered cyclohexadienones has been achieved for the synthesis of benzofurans and cyclopropa­[cd]­indole-carbaldehydes in an operationally simple procedure. Remarkably, the reaction pathway is fully dependent on the linker heteroatom (O or N) present between the cyclohexadienone unit and triazole moiety. In the case of O-linked triazoles, a cascade sequence consisting of intramolecular cyclopropanation and rearrangement takes place, leading to the formation of benzofurans, while, in the case of N-linked triazoles, cyclopropa­[cd]­indole-carbaldehydes were isolated exclusively.

An efficient strategy for the synthesis of structurally diverse homotryptamines and allyl amines via a Rh(II)‐catalyzed tandem reaction of 1,2,3‐triazolyl esters with either indoles or 1,3,5‐trimethoxybenzene has been developed. The reaction proceeds via Rh(II)‐catalyzed intramolecular rearrangement of triazoles into 1‐azadienes followed by regioselective nucleophilic addition. The efficiency of the current protocol was illustrated by broad substrate scope, gram scale synthesis and further functionalization of homotryptamines into other biologically relevant heterocycles.