CuCl-catalyzed radical cyclisation of N-α-perchloroacyl-ketene-N,S- acetals: A new way to prepare disubstituted maleic anhydrides

Andrea Cornia, Fulvia Felluga, Vincenzo Frenna, Franco Ghelfi*, Andrew F. Parsons, Mariella Pattarozzi, Fabrizio Roncaglia, Domenico Spinelli

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The copper-catalyzed radical cyclization (RC) of N-α-perchloroacyl cyclic ketene-N,X(X=O, NR, S)-acetals was studied. While the RC of N-acyl ketene-N,O-acetals was unsuccessful, the 5-endo cyclization of the other ketene acetals provided much better results, with the following order of cyclization efficiency: hexa-atomic cyclic ketene-N,NR-acetals<penta-atomic cyclic ketene-N,S-acetals<hexa-atomic cyclic ketene-N,S-acetals. Invariably the catalytic cycle begins with the formation of a carbamoyl methyl radical. This leads to a cascade of reactions, including a radical polar crossover step, which ends with the formation of the maleimide nucleus, or precursors of this. Products from the RC of the hexa-atomic cyclic ketene-N,S-acetals, were efficiently transformed into disubstituted maleic anhydrides.

Original languageEnglish
Pages (from-to)5863-5881
Number of pages19
JournalTetrahedron
Volume68
Issue number29
DOIs
Publication statusPublished - 22 Jul 2012

Bibliographical note

Funding Information:
We thank the Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR) for financial support ( PRIN 20085E2LXC-004, 20085E2LXC-003 ).

Keywords

  • α-Perchloroenamides
  • 5-endo Radical cyclization
  • Copper(I) chloride
  • Cyclic ketene-N,S-acetals
  • Maleic anhydrides

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