%0 Journal Article
%A Abu-Hasanayn, Faraj
%A Streitwieser, Andrew
%D 1998
%T Kinetics and Isotope Effects of the Aldol−Tishchenko Reaction
between Lithium Enolates and Aldehydes
%U https://acs.figshare.com/articles/journal_contribution/Kinetics_and_Isotope_Effects_of_the_Aldol_Tishchenko_Reaction_between_Lithium_Enolates_and_Aldehydes/3709080
%R 10.1021/jo972128d.s001
%2 https://ndownloader.figshare.com/files/5799633
%K THF
%K 2.0
%K LiSIBP
%K equilibrium isotope effects
%K isotope effect experiments
%K benzaldehyde
%K lithium enolate
%X The lithium enolate of isobutyrophenone reacts with two molecules
of benzaldehyde at room
temperature in THF to yield after protonation a 1,3-diol monoester.
The kinetics of this process
was studied for the reaction of the lithium enolate of
p-(phenylsulfonyl)isobutyrophenone (LiSIBP)
and benzaldehyde in THF by monitoring the disappearance of LiSIBP.
The observed rates obey
the rate law −d[{LiSIBP}]/dt =
kob[{LiSIBP}]0.83[benzaldehyde]2.0
(braces denote initial formal
concentration of LiSIBP) and exhibit a kinetic isotope effect
kH/kD = 2.0 (determined
from
independent experiments using benzaldehyde-d). These
results and competitive isotope effect
experiments are consistent with formation of an initial lithium
aldolate (P1), followed by reaction
with a second aldehyde to form a ketal (P2), and finally a
rate-limiting intramolecular hydride
transfer (Tishchenko reaction). These reactions are modeled with
ab initio molecular orbital
calculations. Corresponding theoretical kinetic and equilibrium
isotope effects match the experimentally observed isotope effects and support the proposed reaction
scheme.
%I ACS Publications