Construction of NH‐Unprotected Spiropyrrolidines and Spiroisoindolines by [4+1] Cyclizations of γ‐Azidoboronic Acids with Cyclic N‐Sulfonylhydrazones

Abstract

The reactions of N -sulfonylhydrazones derived from cyclic ketones with γ-azidopropylboronic acid and 2-(azidomethyl)phenyl)boronic acid give rise to spirocyclic pyrrolidines and spiroisoindolines respectively. The reactions proceed without the need of any transition-metal catalyst through a domino process that comprises the formation of a Csp3-C and a Csp3-N bond of the former hydrazonic carbon. The scope of the reaction have been explored by the preparation of over 50 examples of NH-unprotected spirocyclic derivatives. Importantly, this methodology could be applied for the preparation of alkaloid steroids from steroid N -tosylhydrazones.