Retentive Solvolysis. 16. Reinvestigation of the Retentive Phenolysis of 1-Phenylethyl Chloride. The Mechanism and the Structure of Ion Pair Intermediate
chloride. The pattern C indicates that the first ion pair intermediate, not the second one, is nucleophilically attacked by solvent phenol molecule. The major products were the partially retained o-RC6H4OH, the partially inverted p-RC6H4OH, together with the partially retained ROPh. The same kp–kt pattern C has been observed for the competitive solvolysis of RCl in phenol–methanol (85:15 w/w), which produced
Highly Enantioselective Hydrogenation of Styrenes Directed by 2′-Hydroxyl Groups
作者:Xiang Wang、Anil Guram、Seb Caille、Jack Hu、J P. Preston、Michael Ronk、Shawn Walker
DOI:10.1021/ol200422p
日期:2011.4.1
A new synthetic strategy that turns styrene-type olefins into excellent substrates for Rh-catalyzed asymmetric hydrogenation by Installing a 2'-hydroxyl substituent is described. This methodology accommodates trisubstituted olefinic substrates in various E/Z mixtures, leading to valuable benzylic chiral compounds including (R)-tolterodine. It is also demonstrated that the 2'-hydroxyl groups could be readily removed in high yield without loss of ee from the products. Thus, this technology represents an attractive alternative to the Ir(P-N) catalyst system for the asymmetric hydrogenation of unfunctionalized olefins.
Structural Investigations on Enantiopure P-OP Ligands: A High-Performing P-OP Ligand for Rhodium-Catalysed Hydrogenations
A second generation of phosphine–phosphite (P–OP) ligands, incorporating a larger phosphite group than previous P–OP ligand designs, led to very efficient catalysts for the Rh‐catalyzed enantioselective hydrogenation of a diverse array of substrates (11 examples, 93–99 % ee, mean value of 98 % ee).