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J Org Chem. 2012 Jul 20;77(14):5942-55. doi: 10.1021/jo3004925. Epub 2012 Jul 3.

A combined DFT and NMR investigation of the zinc organometallic intermediate proposed in the syn-selective tandem chain extension-aldol reaction of β-keto esters.

Author information

1
Department of Chemistry, University of New Hampshire, Durham, New Hampshire 03824, USA.

Abstract

The tandem chain extension-aldol (TCA) reaction of β-keto esters provides an α-substituted γ-keto ester with an average syn:anti selectivity of 10:1. It is proposed that the reaction proceeds via a carbon-zinc bound organometallic intermediate potentially bearing mechanistic similarity to the Reformatsky reaction. Evidence, derived from control Reformatsky reactions and a study of the structure of the TCA intermediate utilizing DFT methods and NMR spectroscopy, suggests the γ-keto group of the TCA intermediate plays a significant role in diastereoselectivity observed in this reaction. Such coordination effects have design implications for future zinc mediated reactions.

PMID:
22703563
PMCID:
PMC3401335
DOI:
10.1021/jo3004925
[Indexed for MEDLINE]
Free PMC Article

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