The Banert Cascade: A Synthetic Sequence to Polyfunctional NH-1,2,3-Triazoles

Abstract

A series of polyfunctional NH-1,2,3-triazoles were prepared directly from propargyl halides and nucleophiles using a powerful, albeit little appreciated, synthetic sequence we call the Banert cascade. Propargyl azides, prepared in situ from propargyl halides or sulfonates, underwent a thermal rearrangement sequence to tri­azafulvene intermediates, potent electrophiles, which were readily captured by diverse nucleophiles. Using this cascade, a series of racemic azidomethyl(hydroxymethyl)-NH-1,2,3-triazoles were prepared by a two-step protocol that commences with the addition of propargyl chloride to aldehydes and ketones.

triazoles - heterocycles - azides - rearrangements - alkynes - cyclizations - Banert cascade

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