A highly
enantio- and diastereoselective synthesis of highly functionalized
isochromans was achieved through an organocatalyzed domino reaction.
Quinidine as the catalyst initiates a peroxyhemiacetalization/oxa-Michael/desymmetrization
domino sequence between various 2,5-cyclohexadienone-tethered aryl
aldehydes with hydroperoxides to generate the single diastereomers
of isochromans appended with a cyclohexenone ring bearing three vicinal
stereocenters in good yields and high enantioselectivities under ambient
reaction conditions.
The isochroman scaffold constitutes an important structural unit, which is present in various bioactive natural products and synthetic pharmaceutical compounds exhibiting wide arrays of biological properties. Hence the synthesis of this class of heterocyclic compounds in a stereoselective fashion is highly significant and desirable. In the last decade, a substantial advancement has been witnessed ln the catalytic asymmetric synthesis of isochroman derivatives by employing metal catalysts bearing chiral ligands or by chiral metal‐free organocatalysts. This review aims to provide an overview of the transition metal‐catalyzed and organocatalyzed asymmetric syntheses of isochroman derivatives including isochromenes and isochromanones.magnified image
An unprecedented highly stereoselective synthesis of
pyrrolo[1,2-d][1,4]oxazepin-3(2H)-ones has been accomplished
via photoredox/N-heterocyclic carbene (NHC) relay
catalysis. A wide range of substituted dibenzoxazepines and aryl/hetereoaryl
enals were well accommodated under the organic photoredox catalysis-promoted
amine oxidation to generate the imines, followed by a NHC-catalyzed
[3 + 2] annulation reaction to achieve excellent diastereo- and enantioselectivities
of the dibenzoxazepine-fused pyrrolidinones.
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