Synthesis of ferrocene-substituted 2-azetidinones

J Org Chem. 2001 Dec 28;66(26):8920-5. doi: 10.1021/jo015961q.

Abstract

The photochemical reaction of alkoxychromium(0)carbene complexes and ferrocene mono- and disubstituted imines formed 2-azetidinones having one or two ferrocene moieties in good yields. Yields decrease when the carbene moiety bears an aminoferrocene moiety attached to the carbene carbon, while complex 9 having the ferrocene directly bonded to the carbene carbon was totally inert in these reactions. Access to beta-lactams with the ferrocene tethered to the C3 position through a methylene group was gained using the lithium enolate derived from ethyl 3-ferrocenylpropanoate. The reaction of this enolate produced two unexpected processes. Thus, 2-azetidinone 15 having an hydroxyl group at the C3 position was obtained together with the expected beta-lactam 14, by reaction of the lithium enolate of ethyl 3-ferrocenylpropenoate and imine 1. Additionally, unsaturated amide 17 was obtained by base-promoted Hoffmann-like breakage of the beta-lactam ring formed in the reaction of the same enolate and imine 2. Oxidation of the anion at the C3 of the 2-azetidinone ring on compound 14, as well as the sterically driven ring-breakage of the C3 anion derived from the nonisolated 2-azetidinone 18, should be responsible for this behavior.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Azetidines / chemical synthesis*
  • Ferrous Compounds / chemistry*
  • Indicators and Reagents
  • Lactams / chemical synthesis*
  • Magnetic Resonance Spectroscopy
  • Metallocenes
  • Photochemistry

Substances

  • Azetidines
  • Ferrous Compounds
  • Indicators and Reagents
  • Lactams
  • Metallocenes
  • ferrocene