C-H/C-C Functionalization Approach to N-Fused Heterocycles from Saturated Azacycles

J Am Chem Soc. 2020 Jul 29;142(30):13041-13050. doi: 10.1021/jacs.0c04278. Epub 2020 Jul 19.

Abstract

Herein we report the synthesis of substituted indolizidines and related N-fused bicycles from simple saturated cyclic amines through sequential C-H and C-C bond functionalizations. Inspired by the Norrish-Yang Type II reaction, C-H functionalization of azacycles is achieved by forming α-hydroxy-β-lactams from precursor α-ketoamide derivatives under mild, visible light conditions. Selective cleavage of the distal C(sp2)-C(sp3) bond in α-hydroxy-β-lactams using a Rh-complex leads to α-acyl intermediates which undergo sequential Rh-catalyzed decarbonylation, 1,4-addition to an electrophile, and aldol cyclization, to afford N-fused bicycles including indolizidines. Computational studies provide mechanistic insight into the observed positional selectivity of C-C cleavage, which depends strongly on the groups bound to Rh trans to the phosphine ligand.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aza Compounds / chemistry*
  • Cyclization
  • Heterocyclic Compounds / chemical synthesis*
  • Heterocyclic Compounds / chemistry
  • Indolizidines / chemical synthesis*
  • Indolizidines / chemistry
  • Molecular Structure
  • Stereoisomerism

Substances

  • Aza Compounds
  • Heterocyclic Compounds
  • Indolizidines