Rhodium-catalyzed transannulation of N-sulfonyl-1,2,3-triazoles with vinyl ether has been accomplished for the synthesis of various polysubstituted pyrroles. The present method allows the synthesis of mono-, di-, and trisubstituted pyrroles with appropriate substitutions. Furthermore, the developed methodology was applied in the formal synthesis of neolamellarin A, an antitumor agent.

A general and efficient one-pot aminoethylation of substituted indoles/pyrroles was accomplished for the synthesis of various tryptamine derivatives employing a combination of alkynes and sulfonyl azides as readily accessible aminoethylating agents. The reaction features a successful integration of copper-catalyzed alkyne and azide cycloaddition to N-sulfonyl-1,2,3-triazole, rhodium-catalyzed selective insertion of α-iminocarbenes onto the C3-H bond of indoles, and reduction of the resultant enamides to tryptamine derivatives employing either NaCNBH3 or palladium catalyst, in one-pot. The reaction also showed excellent functional-group tolerance and allowed the synthesis of various substituted tryptamines in good to excellent yield. This transformation constitutes a one-pot formal regioselective functionalization of terminal alkynes. Utility of the synthesized tryptamine was further demonstrated in the synthesis of dihydro-β-carboline and tryptoline.

Suitably substituted electron-deficient 1,2,3-triazoles exist in equilibrium with their ring-opened α-diazoimine tautomers. This phenomenon was used to facilitate the generation of synthetically useful metallo azavinyl carbene intermediates. In this short review, we describe recent developments in the transition-metalcatalyzed decomposition of electron-deficient (annulated) 1,2,3-triazoles to form metallo azavinyl carbenes, and their application in the synthesis of highly functionalized nitrogen-based heterocycles and building blocks through various synthetic transformations, such as transannulation, cyclopropanations, insertion reactions, ylide formation/rearrangements, and ring expansions.

Metal-catalyzed chain-walking reactions have recently emerged as a powerful strategy to functionalize remote positions in organic molecules. However, a chainwalking protocol for nonconjugated dienes remains scarcely reported, and developments are currently ongoing. In this Communication, a nickel-catalyzed asymmetric hydrocyanation of nonconjugated dienes involving a chain-walking process is demonstrated. The reaction exhibits excellent regio-and chemoselectivity, and a wide range of substrates were tolerated, delivering the products in high yields and enantioselectivities. Deuterium-labeling experiments support the chain-walking process, which involves an iterative b-H elimination and reinsertion processes. Gram-scale synthesis, regioconvergent experiments, and downstream transformations gave further insights into the high potential of this transformation. Scheme 1. State of the art and scope of the current work.

An efficient tandem rhodium(II)/squaramide relay catalysis of readily accessible indole derivatives and Nsulfonyl-1,2,3-triazoles has been developed for the enantioselective synthesis of dihydro-β-carbolines in good yield and enantioselectivity. The developed reaction involves selective insertion of in situ generated azavinyl rhodium carbene onto the C3−H bond of indole derivatives and subsequent squaramide-catalyzed enantioselective intramolecular aza-Michael reaction. Furthermore, the potential of the strategy was demonstrated through the ready conversion to potent tetrahydro-β-carbolines and the tetracyclic alkaloid core structure.