Synthesis of 2-substituted pyrimidines and benzoxazoles via a visible-light-driven organocatalytic aerobic oxidation: enhancement of the reaction rate and selectivity by a base
作者:Lin Wang、Zhi-Gang Ma、Xiao-Jing Wei、Qing-Yuan Meng、Deng-Tao Yang、Shao-Fu Du、Zi-Fei Chen、Li-Zhu Wu、Qiang Liu
DOI:10.1039/c4gc00337c
日期:——
An efficient visible-light-driven photocatalytic oxidation of various 2-substituted dihydropyrimidines and phenolic imines has been achieved using an organic photocatalyst eosin Y bis(tetrabutyl ammonium salt) (TBA-eosin Y) and inexpensive oxidant molecular oxygen. With the aid of a base, significantly enhanced photoinduced electron transfer from substrates dihydropyrimidines or phenolic imines to the excited state of TBA-eosin Y has enabled the aerobic oxidation to yield 2-(methylthio)pyrimidines or 2-arylbenzoxazoles selectively.
Chiral Zirconium Catalysts Using Multidentate BINOL Derivatives for Catalytic Enantioselective Mannich-Type Reactions; Ligand Optimization and Approaches to Elucidation of the Catalyst Structure
Catalytic enantioselective Mannich-type reactions of silicon enolates with aldimines were investigated using chiral zirconium catalysts prepared from Zr(O(t)Bu)(4), N-methylimidazole, and newly designed multidentate BINOL derivatives. These new multidentate BINOL ligands were designed on the basis of an assumed transition state structure of a chiral zirconium catalyst derived from two molecules of
Catalytic Asymmetric Strecker Synthesis. Preparation of Enantiomerically Pure α-Amino Acid Derivatives from Aldimines and Tributyltin Cyanide or Achiral Aldehydes, Amines, and Hydrogen Cyanide Using a Chiral Zirconium Catalyst
Strecker amino acid synthesis starting from achiral aldehydes, amines, and HCN using a chiral zirconium catalyst has also been achieved. The three-component asymmetric process reported here significantly improves upon the original Strecker reaction, and has advantages over previous reactions using unstable imines (Schiffbases) as starting materials. Moreover, high yields and enantioselectivities have
Imines derived from aldehydes and 2-aminophenols reacted with allyltrichlorosilanes in the presence of DMF, HMPA, or pyridine N-oxide as a neutral coordinate-organocatalyst to afford the corresponding homoallylic amines in high yields with high stereoselectivity; this is the first example of allylation of imines with allyltrichlorosilanes.
Study on Photochromic Diarylethene with Phenolic Schiff Base: Preparation and Photochromism of Diarylethene with Benzoxazole
作者:Yi Chen、De X. Zeng
DOI:10.1021/jo049565u
日期:2004.7.1
in the solution. In addition, a general preparation of 2-arylbenzoxazole from phenolic Schiff base in the conditions of base and phototrigger is demonstrated by employing phenolic Schiffbases with different substituted groups as template, and other conditions (solvents, in the presence and absence of oxygen) for preparation of benzoxazolefrom phenolic Schiff base are explored as well.