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peri-Dimethylamino substituent effects on proton transfer at carbon in α-naphthylacetate esters: a model for mandelate racemase

Delley, R.J.; Bandyopadhyay, S.; Fox, M.A.; Schliehe, C.; Hodgson, D.R.W.; Hollfelder, F.; Kirby, A.J.; O'Donoghue, A.C.

peri-Dimethylamino substituent effects on proton transfer at carbon in α-naphthylacetate esters: a model for mandelate racemase Thumbnail


Authors

R.J. Delley

S. Bandyopadhyay

C. Schliehe

F. Hollfelder

A.J. Kirby



Abstract

The rate constants for exchange of hydrogen for deuterium at the α-CH2 positions of 8-(N,N-dimethylaminonaphthalen-1-yl)acetic acid tert-butyl ester 1 and naphthalen-1-ylacetic acid tert-butyl ester 2 have been determined in potassium deuteroxide solutions in 1 : 1 D2O : CD3CN, in order to quantify the effect of the neighbouring peri-dimethylamino substituent on α-deprotonation. Intramolecular general base catalysis by the (weakly basic) neighbouring group was not detected. Second-order rate constants, kDO, for the deuterium exchange reactions of esters 1 and 2 have been determined as 1.35 × 10−4 M−1 s−1 and 3.95 × 10−3 M−1 s−1, respectively. The unexpected 29-fold decrease in the kDO value upon the introduction of a peri-dimethylamino group is attributed to an unfavourable steric and/or electronic substituent effect on intermolecular deprotonation by deuteroxide ion. From the experimental kDO values, carbon acid pKa values of 26.8 and 23.1 have been calculated for esters 1 and 2.

Citation

Delley, R., Bandyopadhyay, S., Fox, M., Schliehe, C., Hodgson, D., Hollfelder, F., …O'Donoghue, A. (2012). peri-Dimethylamino substituent effects on proton transfer at carbon in α-naphthylacetate esters: a model for mandelate racemase. Organic and Biomolecular Chemistry, 10(3), 590-596. https://doi.org/10.1039/c1ob06525d

Journal Article Type Article
Acceptance Date Oct 11, 2011
Publication Date Jan 21, 2012
Deposit Date Feb 17, 2012
Publicly Available Date Feb 15, 2016
Journal Organic and Biomolecular Chemistry
Print ISSN 1477-0520
Electronic ISSN 1477-0539
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 10
Issue 3
Pages 590-596
DOI https://doi.org/10.1039/c1ob06525d

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