An
efficient Pd-catalyzed asymmetric allylic substitution cascade
of 4-hydroxy-2H-pyrones with meso-allyl dicarbonates has been developed for the synthesis of kinetic
chiral tetrahydro-1H-pyrano[4,3-b]benzofuran-1-one products in ≤87% yield and ≤99% ee.
The protocol was achieved via a temperature-controlled kinetic control
process, which has been illustrated by means of the experimental results
and control experiments. The reaction could be conducted on a gram
scale, and the resulting product allows for several transformations.
Rh-catalyzed sequential asymmetric
hydrogenations of
3-amino-4-chromones
have been achieved for the first time via an unprecedented dynamic
kinetic resolution under neutral conditions, providing (S,R)-3-amino-4-chromanols in high yields (up to 98%)
with excellent enantio- and diastereoselectivities (up to 99.9% ee
and 20:1 dr). The mechanistic studies based on control experiments
and density functional theory (DFT) calculations suggest that the
dynamic kinetic resolution process for the intermediate enantiomers
generated in the first hydrogenation step proceeded via a stereomutation
(or called chiral assimilation) pathway from an undesired enantiomer
to the desired enantiomer rather than via traditional racemization
of the undesired enantiomer. The protocol can be performed on a gram
scale with a relatively low catalyst loading and offers a practical
and convenient pathway for synthesizing a series of bioactive chromanols
and their derivatives.
The efficient RuPHOX-Ru catalyzed asymmetric hydrogenation of α-substituted tetralones via a dynamic kinetic resolution has been achieved for the synthesis of chiral tetrahydronaphthols. The mechanism study indicated that the hydrogenation...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.