Synlett 2012; 23(16): 2428-2429
DOI: 10.1055/s-0032-1317230
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© Georg Thieme Verlag Stuttgart · New York

Cyclopropenium Ion

Arvind Kumar Yadav
Green Synthesis Lab, Department of Chemistry, University of ­Allahabad, Allahabad 211002, U.P. India   Email: arvindkumaryadav@hotmail.co.in
› Author Affiliations
Further Information

Publication History

Publication Date:
13 September 2012 (online)

Dedicated to my honorable mentor Prof. L. D. S. Yadav

Introduction

The cyclopropenium ion, an aromatic cation, is the smallest member of the Hückel aromatic systems. It was first prepared by Breslow in 1957 as triphenylcyclopropenium perchlorate.[ 1 ] Despite the apparent inherent strain in the cyclopropene ring, cyclopropenium ions possess considerable thermodynamic stability and exhibit the dual properties of stability and ionic charge. Thus, they easily combine with an anion or a Lewis basic heteroatom leading to the reversible generation of the corresponding neutral carbocyclic species (Scheme [1]). Owing to their unique reactivity, cyclopropenium ions, especially 2,3-diarylcyclopropenium ions, have been strategically exploited for the activation of the hydroxyl group of alcohols, carboxylic acids, oximes, and diols in various synthetically useful dehydrative processes to afford alkyl chlorides,[2] [3] acid chlorides,[ 4 ] amides/lactams,[ 5,6 ] and cyclic ethers, respectively.[ 7 ]

Zoom Image
Scheme 1 Cyclopropenium ion
 
  • References

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  • 8 Perkins WC, Wadsworth DH. Synthesis 1972; 205
  • 9 Nogueira JM, Nguyen SH, Bennett CS. Org. Lett. 2011; 13: 2814