DBU-Catalyzed Ring Expansion or Ene-amine Formation Involving δ-Acetoxy Allenoates and <i>N</i>-Sulfonyl Hydrazides
Shabbir Ahmed Khan, A. Sanjeeva Kumar, K. C. Kumara Swamy
Abstract
DBU-catalyzed spiro-annulation and concomitant ring expansion/domino reaction of δ-acetoxy allenoates with cycl-2-ene- N -sulfonyl hydrazides afford ring-expanded (5 → 6, 6 → 7, and 7 → 8) products. By contrast, cycl-3-ene/ane- N -sulfonyl hydrazones under similar conditions deliver pyrazole cores with the same allenoate that involves allylic elimination in which δ-acetoxy allenoate serves as 3C-synthon. The key spirocyclic intermediates, as well as dienyl-amine intermediates, are isolated and characterized. An extension to ( R )-(−)-carvone-derived sulfonyl hydrazide also led to ring expansion and gave pyrazoloazepine.
Topics & Concepts
ChemistrySynthonSulfonylAllylic rearrangementRing (chemistry)Ene reactionAnnulationCatalysisHydrazideMedicinal chemistryStereochemistryOrganic chemistryAlkylSynthetic Organic Chemistry MethodsCatalytic C–H Functionalization MethodsCatalytic Alkyne Reactions