A welcome changein thissituation occurredin 2004with
the demonstration that, akin to the formation of enaminol
from benzaldehyde and NHC, the latter would generate a
homoenolate equivalent from cinnamaldeyde by a conju-
gate umpolung, independently by Glorius7 and Bode.8
Subsequently, a number of groups, including our own,
have exploited homoenolate chemistry for the synthesis of
a variety of important molecular systems, such as spiro-
lactones,9 lactams,10 cyclopentenes,11 cyclopentanones12
and other cyclopentanoids,13 indanes,14 GABA deriva-
tives,15 pyrones,16 pyridazinones,17 etc. Other important
works focusing on the redox chemistry of homoenolates
have also been reported.18
was conceptualized that cinnamaldehyde appended with
2-O-alkenoate, on treatment with NHC, was likely to under-
go a cascade reaction triggered by the initial formation of
homoenolate and its intramolecular Michael addition, and a
series of events culminating in the formation of a coumarin
derivative (Scheme 1).
Scheme 1. Conceptual Framework
Despite the enormous progress in the area of NHC
mediated intermolecular homoenolate chemistry,2 there
are only a few intramolecular homoenolate reactions19
known in the literature. In view of this, intrigued by the
possibility of designing an intramolecular reaction, it
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Of note, coumarin derivatives20 are important synthetic
targets due to their biological properties.21 Inter alia, they
are known to possess potent anticoagulant,22 antitumor,23
vasodilatory,24 anti-HIV,25 and anti-inflammatory26 prop-
erties. Some coumarin derivatives are endowed with useful
fluorescent properties.27
Thus, from both mechanistic and synthetic standpoints
the pursuit of an intramolecular homoenolate reaction
shown in Scheme 1 was considered worthwhile. The results
of our investigation form the subject matter of this paper.
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