ISSN:
0894-3230
Keywords:
Organic Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Base-catalysed substrate-enantioselective 1,3-hydron transfer (kinetic resolution) was studied in the indene system. A series of 1-methylindenes substituted in the aromatic ring [5-methoxy- (2), 5-fluoro- (3), 5-nitro- (4) and 7-nitro (5)] and 1-methylindene (1) were employed as substrates. The rate constants, the enantioselectivities and the kinetic isotope effects (KIEs) for the enantioselective reactions [(kH/kD)+ and (kH/kD)-] were determined at 20°C using (+)-(8R, 9S)-dihydroquinidine as chiral catalyst in the solvent o-dichlorobenzene. The rate constants vary according to the elecronic effects of the substituents. The primary deuterium KIE, ranging from 4·73 [for (+)-(S)-2] to 11·3 [for (-)-(R)-5], is correlated with the rate constants as expected on the basis of the Melander-Westheimer postulate. The introduction of a substituent in the aromatic ring decreases the enantioselectivity. All compounds except 5 show the same sense of the enantioselectivity [k+/k- 〉 1; all substrates used are (+)-(S)/(-)-(R)]. The enantiomer dependence of the KIE is most pronounced for 1 [(kH/kD)+ = 5·71 and (kH/kD)- = 6·46] and vanishes for the most acidic substrates (4 and 5).
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/poc.610080604
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