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email.gif - 0.3 KECHET96 Article 005: Masaru Tada

Steric crowding alters the reaction pathway for sulfoxide electrophilic substitution (SES)

Xia Shao, Jeffery Kohrt and Dallas K. Bates*

Department of Chemistry, Michigan Technological University, Houghton, MI 49931


Sulfoxide electrophilic sulfenylation (SES) is a useful technique for heterocyclic synthesis (eqn. 1). We have exploited pyrrole-containing sulfoxides for intramolecular sulfenylation to form a wide variety of N,S- heterocycles.

The present study was initiated to prepare pyrrolopyrimidine derivatives. However the reaction, unexpectedly, gave pyrrolinones as major products in addition to the expected heterocycles. The pyrrolinones have not been reported previously in SES or Pummerer reactions and appear to be formed due to steric crowding of ring substituents around the pyrrole.

In this preliminary report we present our findings for two pyrimidine systems: (1) and (2), prepared from commercially available 5-amino-4,6-dichloropyrimidine and 4-amino-5-chloro-2,6-dimethylpyrimidine, respectively, using standard procedures. Typical SES reaction conditions (trifluoroacetic anhydride in N,N-dimethylformamide at 0 celsius) produced products 3, 4 and 5-7, respectively, from 1 and 2.

  • Introduction
  • Results
  • Mechanistic proposals
  • Conclusions
  • Acknowledgements