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.

Key words

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

References

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14

Manetsch, R.; Loren, J. C.; Sharpless, K. B.; Kolb, H. C. unpublished results.

18

This product was anticipated based on the results described by Banert using methanol both as solvent and nucleophile. [12a-c]

24

Loren, J. C.; Speers, A. E.; Cravatt, B. F.; Fokin, V. V.; Sharpless, K. B. unpublished results.