Effect of Aryl Substituents on Intramolecular Cyclization of 2,2’-Biphenoquinones
摘要:
Effect of aryl substituents on intramolecular cyclizations of 3,3',5,5'-tetraaryl-2,2'-biphenoquinones (Ar = phenyl (1a) and 4-methoxyphenyl (1b)) has been studied. In benzene, 1a gave 2,4,6,8-tetraphenyldibenzofuran-1-ol (10) gradually as a main product, indicating the phenyl substituents preferred to stabilize the intermediate by delocalization of the negative charge rather than that of the positive one. In contrast, the reaction of 1b occurred spontaneously in order to give a complex mixture, which should be due to 4-methoxyphenyl substituent at the 3 position.
Counteranion-controlled regioselectivity in palladium-catalyzed allylic amination of dienyl allylic carbonates
作者:Meng-Lan Shen、Pu-Sheng Wang、Liu-Zhu Gong
DOI:10.1016/j.tet.2021.131996
日期:2021.3
A regioselective Pd-catalyzed allylic amination reaction of dienyl allylic carbonates and aromatic amines has been developed by means of phosphoramidte-palladium catalysis. The regioselectivity could be altered by the counterion of the π-allylpalladium intermediate. As a result, either branched Z-dienyl allylic amines or linear conjugated allylic amines were generated in high levels of regioselectivity
The synthesis and characterization of seven new phosphoramidite ligands are described, as well as their use in copper-catalyzed 1,4-addition of diethylzine to a wide range of substrates. Enantioselectivities of up to >99.5% are obtained. (C) 2004 Elsevier Ltd. All rights reserved.
Flash photolysis study of the kinetics of the destruction of mono- and disubstituted phenoxyl radicals