Catalytic asymmetric syntheses of various isoxazoline-N-oxides have been accomplished by asymmetric phase-transfer conjugate addition of bromomalonate to nitroolefins and subsequent ring-closing O-alkylation.
Catalytic asymmetric synthesis of various isoxazoline-N-oxides having a tetrasubstituted carbon has been accomplished by asymmetric phase-transfer conjugate addition of bromomalonate to nitroolefins and subsequent ring-closing O-alkylation. The obtained isoxazoline-N-oxide was readily converted to the corresponding oxime, isoxazoline, and lactam without loss of optical purity.
Palladium-Catalyzed Asymmetric Decarboxylative [4+2] Dipolar Cycloaddition of 4-Vinyl-1,3-dioxan-2-ones with α,β-Disubstituted Nitroalkenes Enabled by a Benzylic Substituted P,N-Ligand
The Pd-catalyzed asymmetric [4+2] cycloaddition reaction of an aliphatic 1,4-dipole with singly activated electron-deficient alkenes is realized for the first time, enabled by using a newly developed benzylic substituted P,N-ligand, affording tetrahydropyrans having three continuous chiral centers in high yields with high diastereo- and enantioselectivities. The rational transition states of the reaction as well as the role of the benzylic chiral center are proposed.
Dynamic Kinetic Asymmetric Ring-Opening/Reductive Amination Sequence of Racemic Nitroepoxides with Chiral Amines: Enantioselective Synthesis of Chiral Vicinal Diamines
作者:Juan Agut、Andreu Vidal、Santiago Rodríguez、Florenci V. González
DOI:10.1021/jo400501k
日期:2013.6.7
We report a highly diastereoselective synthesis of vicinaldiamines by the treatment of nitroepoxides with primary amines and then a reducing agent. When using a chiral primary amine, racemic nitroepoxides are transformed into chiral diamines as a single enantiomers (>95:5 er) through a dynamic kinetic asymmetric transformation (DYKAT). The overall process is a one-pot procedure combining the exposure