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Rotational isomers of N-methyl-N-arylacetamides and their derived enolates: Implications for asymmetric Hartwig oxindole cyclizations

Mandel, J and Pan, X and Hay, EB and Geib, SJ and Wilcox, CS and Curran, DP (2013) Rotational isomers of N-methyl-N-arylacetamides and their derived enolates: Implications for asymmetric Hartwig oxindole cyclizations. Journal of Organic Chemistry, 78 (8). 4083 - 4089. ISSN 0022-3263

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Abstract

The rotational preferences of N-(2-bromo-4,6-dimethylphenyl)-N-methyl 2-phenylpropanamide were studied as a model of precursors for Hartwig asymmetric oxindole cyclizations. The atropisomers of this compound were separated by flash chromatography, and then the enantiomers were resolved and the interconversions of the stereocenter and the N-Ar axis were studied. Under thermal conditions, the axis is very stable. Under the basic conditions of the Hartwig cyclization, both the stereocenter and the chiral axis equilibrate via enolate formation. The N-Ar rotation barrier of a 2-phenylacetamide analogue was reduced from 31 kcal mol-1 in the precursor to 17 kcal mol -1 in the enolate. Reasons for this dramatic barrier reduction and implications of both N-Ar and amide C-N rotations for Hartwig cyclizations are discussed. © 2013 American Chemical Society.


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Details

Item Type: Article
Status: Published
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Mandel, J
Pan, X
Hay, EB
Geib, SJgeib@pitt.eduGEIB0000-0002-9160-7857
Wilcox, CSdaylite@pitt.eduDAYLITE
Curran, DPcurran@pitt.eduCURRAN
Date: 19 April 2013
Date Type: Publication
Journal or Publication Title: Journal of Organic Chemistry
Volume: 78
Number: 8
Page Range: 4083 - 4089
DOI or Unique Handle: 10.1021/jo400385t
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Refereed: Yes
ISSN: 0022-3263
MeSH Headings: Benzeneacetamides--chemistry; Cyclization; Indoles--chemistry; Phenylpropionates--chemistry; Stereoisomerism
Other ID: NLM NIHMS463046 [Available on 04/19/14], NLM PMC3653423 [Available on 04/19/14]
PubMed Central ID: PMC3653423
PubMed ID: 23534372
Date Deposited: 04 Mar 2014 19:40
Last Modified: 16 Mar 2019 14:55
URI: http://d-scholarship.pitt.edu/id/eprint/20672

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