Campus Units

Chemistry

Document Type

Article

Publication Version

Published Version

Publication Date

7-2007

Journal or Book Title

Organometallics

Volume

26

Issue

16

First Page

3995

Last Page

4002

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

Included in

Chemistry Commons

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