Catalysis of .alpha.-hydrogen exchange. IX. Isobutyraldehyde-2-d exchange in the presence of amino acids

Hine, Jack; Menon, B. C.; Mulders, Julien; Flachskam, Robert L.

doi:10.1021/jo01264a070

Cited by 10 publications

(3 citation statements)

References 4 publications

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“…The rate constants at three temperatures for both solvents are given in Table I. Duplicate runs were made at each point, and 6 ,14 X 10-4 0.999 25.0 1 .58 X 10-5 0.999 32.5 3 .85 X 10-= 0.997 the reported rates are the resulting mean.…”

Section: Resultsmentioning

confidence: 99%

Competitive solvolytic homoconjugation

Lambert¹,

Jovanovich²,

Hamersma³

et al. 1973

J. Am. Chem. Soc.

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m-Bicyclo[5.1.0]oct-5-en-3-yl tosylate (c/í-1-OTs) exists in two conformational forms that solvolyze by independent pathways. The less stable (saddle) conformer (2) solvolyzes with double bond participation to form cis-1 (corresponding to retained starting material) and various hydride-shifted materials. The more stable (boat-chair) conformer 3 solvolyzes with cyclopropane participation to give the cz'j-bicyclo[5.1.0]oct-4-en-3-yl ester (cis-7). Quantitative product analysis indicates that about 80 % of the reaction occurs by double bond participation and 20% by cyclopropane participation. The study thus furnishes a direct comparison of the two forms of participation under competitive circumstances.(16) We are indebted to Professor John Grutzner, Purdue University, for these deuterium spectra, taken on a Varían XL-100.

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Section: Resultsmentioning

confidence: 99%

Competitive solvolytic homoconjugation

Lambert¹,

Jovanovich²,

Hamersma³

et al. 1973

J. Am. Chem. Soc.

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“…Similar results were obtained for theaminoalkanoic acids containing 2, 3, 4, 5, and 6 carbon atoms. 21 We hypothesized that this lack of bifunctional catalysis arose in part from steric hindrance of the type indicated by the double-headed arrow in 2. In order for the dimethylamino group to reach the «-deuterium atom with chains of the length we were dealing with, there must be a cis orientation around the double bond of the reacting iminium ion.…”

Section: Bifunctional Catalysis Of the Dedeuteration Of Me2cdchomentioning

confidence: 99%

Bifunctional catalysis of .alpha.-hydrogen exchange of aldehydes and ketones

Hine¹

1978

Acc. Chem. Res.

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Polyfunctional catalysis contributes greatly to the remarkable catalytic activity and selectivity of enzymes. Studies of enzymes and reactions they bring about have taught us much about such catalysis.2,3 However, the high molecular weights of enzymes and the large number of functional groups in each molecule cause difficulties and ambiguities. We therefore wished to study relatively simple reactions proceeding by enzyme-like mechanisms. We started with reactions in which: (1) the catalyst uses one functional group to form a complex with, and perhaps activate, the substrate; (2) a second functional group brings about the desired reaction on the complexed substrate; (3) the complexed product is released.

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“…The observed rate constant for deuterium exchange into glycine methyl ester is increased by up to 1000-fold in the presence of acetone and phosphate buffer . Amines, including α-amino acids, provide very effective catalysis of deprotonation of aldehydes and ketones via the formation of iminium ion adducts ( 1 , H α ‘). − Catalysis of deprotonation of α-amino acids through this adduct ( 1 , H α ) might have been predicted, but not with such enormous catalytic power. In any event, there have been few reports of catalysis of carbon deprotonation of α-amino acids by ketones and no studies of the mechanism of this reaction.…”

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confidence: 99%