N‐Alkenyl compounds are versatile synthetic building blocks and their stereoselective transformations are key processes in the synthesis of many prominent classes of natural products, pharmaceuticals, and agrochemicals. However, a large structural variety of known N‐alkenyl compounds and their diverse reactivity have so far precluded the development of a general method for their stereoselective synthesis. Herein we present an aluminum halide‐mediated, highly stereoselective, efficient and scalable transformation of commercially available N‐fluoroalkyl‐1,2,3‐triazoles to N‐haloalkenyl imidoyl halides, and demonstrate their use in the synthesis of stereodefined N‐alkenyl amides, amidines, imines, hydrazonoamides, imidothioates, iminophosphonates, 1,2,4‐triazoles and tetrazoles. The reaction is of wide scope on both the triazole substrate and aluminum halide, providing highly functionalized products. Mechanistic and computational investigations suggest a reaction mechanism involving the triazole ring opening, initiated by the coordination of nitrogen one of the triazole ring to the Lewis acid, N2 elimination and the formation of a vinyl cation intermediate, which reacts with nitrogen‐bound aluminum halide, followed by a series of halide exchange reactions on C−X and Al−X bonds.
The stereoselective Suzuki–Miyaura cross-coupling of (Z)-β-enamido triflates is demonstrated. Depending on the nature of the ligand in the palladium catalyst, either retention or inversion of the configuration during the synthesis of β,β-diaryl-substituted enamides is observed. Thus, the method provides synthetic access to both isomers of the target enamides from (Z)-β-enamido triflates.
The front cover picture illustrates the reaction of N‐fluoroalkylated‐1,2,3‐triazoles with aluminum trihalide, proceeding via a vinyl cation (illustrated as the structure in brackets in the middle) to afford structurally diverse N‐haloalkenyl imidoyl halides. These products are formed in a stereoselective fashion on both double bonds and have been utilized in the synthesis of various N‐alkenyl compounds, such as enamides, enamidines, enimines, N‐alkenyl tetrazoles, and other. In this work, Beier and co‐workers show a new, mild and efficient 1,2,3‐triazole denitrogenative ring‐opening process mediated by easily available Lewis acids. Details can be found in the Full Paper by Beier and co‐workers (A. Markos, L. Janecký, T. Chvojka, T. Martinek, H. Martinez‐Seara, B. Klepetářová, P. Beier, Adv. Synth. Catal. 2021, 363, 3258–3266; DOI: 10.1002/adsc.202100009).
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