The Suzuki−Miyaura Cross-Coupling−Claisen Rearrangement−Cross-Metathesis Approach to Prenylated Isoflavones
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Date
2022
Journal Title
Journal ISSN
Volume Title
Publisher
American Chemical Society
Abstract
Isoflavones were synthesized via Suzuki−Miyaura
coupling of 3-iodochromones and para-methoxybenzene- and para-
phenolboronic acid. In our hands, conditions commonly used for
similar cross couplings turned out to be unsuccessful or difficult to
reproduce, for example, due to the unplanned partial cleavage of
MOM-protecting groups. Using Pd(dba)2 as a precatalyst and
tricyclohexylphosphine as an activating ligand, reliable cross-coupling
conditions were identified. In all cases, notably higher yields of
isoflavones were obtained with para-phenolboronic acid than with
para-methoxybenzene boronic acid. This observation and the
commercial availability of para-phenolboronic acid suggest that for
the synthesis of the important 3′-prenyl- or 3′,5′-diprenylisoflavone
substitution pattern a synthetic route that introduces the prenyl
substituents after the Pd-catalyzed cross-coupling step, thereby
avoiding laborious and protecting-group-intensive multistep syntheses of C-prenylated arene boronic acids, is advantageous
Description
Keywords
The Suzuki, Miyaura Cross, Coupling, Claisen Rearrangement, Cross, Metathesis Approach to Prenylated Isoflavones