A novel catalyst-free synthetic approach to 1,2,3-triazolobenzodiazepinones has been developed and optimized. The Ugi reaction of 2-azidobenzaldehyde, various amines, isocyanides, and acids followed by microwave-assisted intramolecular azide–alkyne cycloaddition (IAAC) gave a series of target heterocyclic compounds in moderate to excellent yields. Surprisingly, the normally required ruthenium-based catalysts were found to not affect the IAAC, only making isolation of the target compounds harder while the microwave-assisted catalyst-free conditions were effective for both terminal and non-terminal alkynes.
Halodiazirines emerged as very useful reagents in photochemically- or thermally-mediated cyclopropanation reactions with alkenes. This Short review highlights the synthetic applications of these reagents as precursors of halocarbenes with various alkenes.
Only few efficient methods for the preparation of polyazoles containing three or four nitrogen atoms in each azole cycle exist. We have developed a novel synthetic strategy that allows the sequential assembly of 1,2,3‐triazole, 1,2,4‐triazole, and tetrazole fragments into a new stable polyazole. Along the novel strategy, some known procedures have been optimized to achieve better conversion, selectivity, and, in general, overall efficiency.
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