α-Alkylation of N–C Axially Chiral Quinazolinone Derivatives Bearing Various ortho-Substituted Phenyl Groups: Relation between Diastereoselectivity and the ortho-Substituent
作者:Osamu Kitagawa、Mizuki Matsuoka、Asumi Iida
DOI:10.1055/s-0037-1610110
日期:2018.10
C–N axially chiral structure at ambient temperature. The reactions of alkyl halides with the anionic species prepared from these quinazolinones were systematically explored. The α-alkylation reactions proceeded with diastereoselectivities ranging from 1:1 to >50:1, depending upon the steric bulk of the ortho-substituent, to afford products having the elements of axial and central chirality in high yields
In the presence of (R)-DTBM-SEGPHOS-Pd(OAc)2 catalyst, treatment of various 3-(2,6-dibromophenyl)quinazolin-4-ones with NaBH4 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
The reaction of various optically pure N–C axially chiral quinazolin-4-one derivatives with Lawesson’s reagent proceeded without a marked decrease in optical purity to give optically active quinazoline-4-thione derivatives (93–99% ee) possessing a high rotational barrier in good yields.