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Catalytic Enantioselective Synthesis of N–C Axially Chiral Mebroqualone and Its Derivatives through Reductive Asymmetric Desymmetrization
In the presence of
(<i>R</i>)-DTBM-SEGPHOS-PdÂ(OAc)<sub>2</sub> catalyst, treatment
of various 3-(2,6-dibromophenyl)Âquinazolin-4-ones
with NaBH<sub>4</sub> gave optically active N–C axially chiral
quinazolinone (mebroqualone) derivatives through reductive asymmetric
desymmetrization (enantioselective monohydrodebromination) followed
by kinetic resolution of the resulting monobromophenyl products (up
to 99% ee). The enantioselectivity strongly depended on the substituent
(R<sup>2</sup>) at the C4′position, amount of NaBH<sub>4</sub>, and reaction temperature