428842-08-4Relevant articles and documents
Kinetics of reaction of β-alkoxyvinyltrifluoromethyl ketones with nucleophiles containing amino groups
Vdovenko, Sergei I.,Gerus, Igor I.,Gorbunova, Marina G.
, p. 167 - 169 (1997)
The reaction kinetics of β-alkoxyvinylalkyl ketones with nucleophiles containing amino groups are strongly dependent upon the substituent on the C atom of the carbonyl group, solvent polarity and structure of the amino-containing nucleophiles.
Steric effects on the mechanism of reaction of nucleophilic substitution of β-substituted alkoxyvinyl trifluoromethyl ketones with four secondary amines
Vdovenko, Sergey I.,Gerus, Igor I.,Kukhar, Valery P.
, p. 190 - 200 (2008/02/06)
The kinetics of the reaction of β-substituted β-alkoxyvinyl trifluoromethyl ketones R1-CR2= CH-COCF3 (la-e) [(la), R1=C2H5, R2=H; (1b), R 1=R2=CH3; (1c), R1=C 2H5, R2=C6H5; (1d), R1 = C2H5, R2=V-pNO 2C6H4; (1e), R1=C2H 5, R2=C(CH3)3] with four aliphatic amines (2a-d) [(2a), (C2H5)2NH; (2b), (i-C 3H7)2NH; (2c), (CH2)5NH; (2d), O(CH2CH2)2NH] was studied in two aprotic solvents, hexane and acetonitrile. The least reactive stereoisomeric form of (la-d) was the most populated (E-s-Z-o-Z) form, whereas in (1e), the more reactive form (Z-s-Z-o-Z) dominated. The reactions studied proceeded via common transition state formation whose decomposition occurred by 'uncatalyzed' and/or 'catalyzed' route. Shielding of the reaction centre by bulky β-substituents lowered abruptly both k′ ('uncatalyzed' rate constant) and k″ ('catalyzed' rate constant) of this reaction. Bulky amines reduced k″ to a greater extent than k′ as a result of an additional steric retardation to the approach of the bulky amine to its ammonium ion in the transition state. An increase in the electron-withdrawing ability of the β-substituent increased 'uncatalyzed' k′ due to the acceleration of the initial nucleophile attack (k1) and 'uncatalyzed' decomposition of transition state (k2) via promoting electrophilic assistance (through transition state 8). The amine basicity determined the route of the reaction: the higher amine basicity, the higher k3/k2 ratio (a measure of the 'catalyzed' route contribution as compared to the 'uncatalyzed' process) was. 'Uncatalyzed' route predominated for all reactions; however in polar acetonitrile the contribution of the 'catalyzed' route was significant for amines with high pKa and small bulk. Copyright
