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G. G. GATEV, M. ZHONG AND J. I. BRAUMAN
benzoate, SN2 (28%) and transacylation products (72%)
were observed.13 In the reaction of methoxide and methyl
trifluoroacetate, the SN2 channel accounts for at least 90% of
the products.14 In the reaction with methyl cyanoformate,
we observed that methoxide produced 63% NCCO2Ϫ via the
SN2 channel, but this channel probably accounts for as much
as 100% of the products, since the CNϪ is formed mainly
via the SN2 channel similar to the benzyl anion.
From Table 3, we find that when methoxide reacts with
the series HCOOMe, PhCOOMe, CF3COOMe, as the
leaving group become better more of the SN2 product is
observed. Transacylation is observed unambiguously only
when the carboxylate ion cannot decompose to form RϪ
ion.
If we compare the reactivity of methoxide and benzyl
anions, we find that in the reaction with methyl benzoate the
methoxide produces more of the SN2 product, 28% com-
pared with 13%. Similarly, for methyl trifluoroacetate,
methoxide reacts at least 90% via the SN2 channel, which
for the benzyl ion is no more than 63%. With the methyl
cyanoformate both compounds react mainly through the SN2
channel.
ACKNOWLEDGMENTS
We thank the National Science Foundation for support of
this research. G.G.G. gratefully acknowledges the assis-
tance of the Salgo–Noren Foundation. This paper is
dedicated to Fred Bordwell in appreciation of his many
important contributions to physical organic chemistry.
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In the reaction of benzyl ion with methyl benzoate,
methyl cyanoformate and methyl trifluoroacetate, both SN2
and transacylation are observed, similarly to methoxide.
The better the leaving group, the more of the SN2 products
are observed.
© 1997 by John Wiley & Sons, Ltd.
JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, VOL. 10, 531–536 (1997)