Issue in Honor of Prof. Albert Padwa ARKIVOC 2002 (viii) 16-33
N-H Insertion reactions of rhodium carbenoids. Part 4.1 New chiral dirhodium(II) carboxylate catalysts
Richard T. Buck, Christopher J. Moody*, and Adrian G. Pepper
School of Chemistry, University of Exeter, Stocker Road, Exeter EX4 4QD, UK E-mail:
[email protected]
Dedicated to Professor Albert Padwa in recognition of his outstanding contributions to the dirhodium(II) catalysed chemistry of diazocarbonyl compounds (received 01 May 02; accepted 31 May 02; published on the web 08 Jun 02)
Abstract The reaction of methyl 2-diazophenylacetate 1 and dimethyl a-diazobenzylphosphonate 2 with various N-H components in the presence of chiral dirhodium(II) catalysts results in N-H insertion in good yield but with little or no stereoselectivity.
Keywords: Diazoester, diazophosphonate, carbene insertion, rhodium, catalyst
Introduction
The synthesis of a-amino acids and peptides remains a topic of considerable importance and current interest. In previous papers,2,3 we have reported that diazoesters react with a range of R3NH2 compounds in the presence of dirhodium(II) catalysts to give a-amino acid derivatives, the products of N-H insertion of the intermediate rhodium carbene, in high yield (Scheme 1).
R3NH2 cat. Rh(II) R1 CO2R2 N2 R1 CO2R2 NHR3 H Scheme 1
In an extension to this work,4 we showed that N-protected amino acid amides also underwent N-H insertion reaction, in a new approach to dipeptides (Scheme 2).
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