Two approaches to diverting the course of a free-radical cyclization: application of cyclopropylcarbinyl radical fragmentations and allenes as radical acceptors

J Org Chem. 2009 Nov 20;74(22):8726-32. doi: 10.1021/jo901834q.

Abstract

Free radical cyclization of 4 and 7 gave the expected cyclization-reduction products (5 and 8) along with considerable amounts of products derived from a cyclization-atom transfer-secondary cyclization process (6 and 9). Two approaches to avoiding these unexpected products were explored. Use of a cyclopropylcarbinyl fragmentation avoided the secondary cyclization reaction (25 or 43 --> 26 or 44), whereas use of an allene as a radical acceptor avoided the atom-transfer reaction altogether (49 --> 52).

MeSH terms

  • Alkanes / chemistry*
  • Cyclization
  • Cyclopropanes / chemical synthesis*
  • Cyclopropanes / chemistry
  • Free Radicals / chemical synthesis
  • Free Radicals / chemistry
  • Molecular Conformation
  • Stereoisomerism

Substances

  • Alkanes
  • Cyclopropanes
  • Free Radicals