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Article
Iron Porphyrin Catalyzed N−H Insertion Reactions with Ethyl Diazoacetate
Organometallics
  • Lynette K. Baumann, Iowa State University
  • Harun M. Mbuvi, Iowa State University
  • Guodong Du, Iowa State University
  • L. Keith Woo, Iowa State University
Document Type
Article
Disciplines
Publication Version
Published Version
Publication Date
7-1-2007
DOI
10.1021/om0610997
Abstract
A series of metalloporphyrin complexes were surveyed as catalysts for carbene insertion from ethyl diazoacetate into the N−H bonds of amines. Iron(III) tetraphenylporphyrin chloride, Fe(TPP)Cl, was found to be an efficient catalyst for N−H insertion reactions with a variety of aliphatic and aromatic amines, with yields ranging from 68 to 97%. Primary amines were able to undergo a second insertion when another equiv of EDA was added by slow addition. N-Heterocyclic compounds were poor substrates, giving low yields or no N−H insertion products. Competition reactions and linear free energy relationships provided mechanistic insights for the insertion reaction. The relative rates for N−H insertion into para-substituted aniline derivatives correlated with Hammett σ+ parameters. Electron-donating groups enhanced the reaction, as indicated by the negative value of ρ (ρ = −0.66 ± 0.05, R2 = 0.93). These results are consistent with a rate-determining nucleophilic attack of the amine on an iron carbene complex. In addition, the decomposition of EDA catalyzed by FeII(TPP) or FeIII(TPP)Cl was examined with various amounts of added pyridine. The Fe(II) catalyst is strongly inhibited by the presence of pyridine. In contrast, catalysis by the Fe(III) porphyrin is accelerated by amines. These experiments suggested that an iron(III) porphyrin carbene complex is the active catalyst.
Comments

Reprinted (adapted) with permission from Organometallics 26 (2007): 3995, doi:10.1021/om0610997. Copyright 2007 American Chemical Society.

Copyright Owner
American Chemical Society
Language
en
File Format
application/pdf
Citation Information
Lynette K. Baumann, Harun M. Mbuvi, Guodong Du and L. Keith Woo. "Iron Porphyrin Catalyzed N−H Insertion Reactions with Ethyl Diazoacetate" Organometallics Vol. 26 Iss. 16 (2007) p. 3995 - 4002
Available at: http://works.bepress.com/l-woo/27/