1,3-HYDRON TRANSFER IN SOME 5-SUBSTITUTED AND 7-SUBSTITUTED 1-METHYLINDENES - ENANTIOSELECTIVITIES AND ENANTIOMER-DEPENDENT KINETIC ISOTOPE EFFECTS
1995 (English)In: JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, ISSN 0894-3230, Vol. 8, no 6, 400-406 p.Article in journal (Refereed) Published
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 [(k(H)/k(D))(+) and (k(H)/k(D))(-)] were determined at 20 degrees C using (+)-(8R, 9S)-dihydroquinidine as chiral catalyst in the solvent o-dichlorobenzene. The rate constants vary according to the electronic 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 [(k(H)/k(D))(+) = 5 . 71 and (k(H)/k(D))(-) = 6 . 46] and vanishes for the most acidic substrates (4 and 5).
Place, publisher, year, edition, pages
1995. Vol. 8, no 6, 400-406 p.
1;3-PROTOTROPIC REARRANGEMENT; CINCHONA ALKALOIDS; COMBINED NMR
IdentifiersURN: urn:nbn:se:uu:diva-68656OAI: oai:DiVA.org:uu-68656DiVA: diva2:96567