Construction of NH‐Unprotected Spiropyrrolidines and Spiroisoindolines by [4+1] Cyclizations of γ‐Azidoboronic Acids with Cyclic <i>N</i>‐Sulfonylhydrazones
Lucía López, María‐Paz Cabal, Carlos Valdés
Abstract
Abstract The reactions of N ‐sulfonylhydrazones derived from cyclic ketones with γ‐azidopropylboronic acid and 2‐(azidomethyl)phenylboronic 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 Csp 3 ‐C and a Csp 3 ‐N bond of the former hydrazonic carbon. The scope of the reaction has 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.
Topics & Concepts
ChemistryCatalysisDominoMedicinal chemistryPhenylboronic acidOrganic chemistryCyclopropane Reaction MechanismsSynthesis and Catalytic ReactionsCatalytic C–H Functionalization Methods