We report a Michael-type
cyanation reaction of coumarins by
using CO2 as a catalyst. The delivery of the nucleophilic
cyanide was realized by catalytic amounts of CO2, which
forms cyanoformate and bicarbonate in the presence of water. Under
ambient conditions, CO2-catalyzed reactions afforded high
chemo- and diastereoselectivity of β-nitrile carbonyls, whereas
only low reactivities were observed under argon or N2.
Computational and experimental data suggest the catalytic role of
CO2, which functions as a Lewis acid, and a protecting
group to mask the reactivity of the product, suppressing byproducts
and polymerization. The utility of this convenient method was demonstrated
by preparing biologically relevant heterocyclic compounds with ease.
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