Regiocontrol and Stereoselectivity in Tungsten-Bipyridine Catalysed Allylic Alkylation
摘要:
Tungsten-bipyridine complexes, generated in situ, catalyse the allylic alkylation of isocinnamyl methyl carbonate by dimethyl sodiomalonate [NaCH(CO2CH3)(2)] with complete syn-stereoselectivity. When para substituted aryl-allyl methyl carbonates are employed, the regioselectivity correlates with Swain-Lupton parameters. Cross-over experiments demonstrate that the reactions do not procede via the conventional [M(0)] --> [M(II) allyl](+) --> [M(0) allyl-Nu] catalytic cycle.
Molybdenum-catalyzedasymmetricallylicalkylationreactions were carried out using the inexpensive, air-stable, and readily available Mo(CO)6 as precatalyst. In situ IR was used to determine the required activation time and temperature required to achieve the maximum concentration of the ‘‘active’’ catalyst from the molybdenum-precatalyst and chiral ligand. Results from comparison studies are consistent
An efficient Ru-catalyzed regioselective allylictrifluoromethylthiolation reaction of allylic carbonates was developed. The linear allylictrifluoromethylthioethers were obtained in 52–91% yields. Mechanistic investigation revealed that this reaction proceeds via a double allylictrifluoromethylthiolation sequence.
Readily Available [2.2.2]-Bicyclooctadienes as New Chiral Ligands for Ir(I): Catalytic, Kinetic Resolution of Allyl Carbonates
作者:Christian Fischer、Christian Defieber、Takeyuki Suzuki、Erick M. Carreira
DOI:10.1021/ja0390707
日期:2004.2.1
We report an Ir(I)-catalyzed kinetic resolution of secondary allylic carbonates allowing for their isolation in up to 98% ee. Importantly, the study documents the synthesis and use of a new class of chiral [2.2.2]-bicyclooctadiene ligands for iridium.
Regiocontrol and Stereoselectivity in Tungsten-Bipyridine Catalysed Allylic Alkylation
作者:Jürg Lehmann、Guy C. Lloyd-Jones
DOI:10.1016/0040-4020(95)00481-m
日期:1995.8
Tungsten-bipyridine complexes, generated in situ, catalyse the allylic alkylation of isocinnamyl methyl carbonate by dimethyl sodiomalonate [NaCH(CO2CH3)(2)] with complete syn-stereoselectivity. When para substituted aryl-allyl methyl carbonates are employed, the regioselectivity correlates with Swain-Lupton parameters. Cross-over experiments demonstrate that the reactions do not procede via the conventional [M(0)] --> [M(II) allyl](+) --> [M(0) allyl-Nu] catalytic cycle.