42451-57-0Relevant academic research and scientific papers
Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts
Oestreich, Martin,Seliger, Jan
, p. 247 - 251 (2020/10/29)
A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition-metal-catalyzed alcohol racemization and enantioselective Cu-H-catalyzed dehydrogenative Si-O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Often-used ruthenium half-sandwich complexes are not suitable but a bifunctional ruthenium pincer complex perfectly fulfills this purpose. By this, enantioselective silylation of racemic alcohol mixtures is achieved in high yields and with good levels of enantioselection.
Analysis of the enantioselectivities and initial rates of the hydrosilylation of acetophenone catalyzed by [Rh(cod)Cl]2/(chiral diphosphine). The quantitative analysis of ligand effects
Reyes, Clementina,Prock, Alfred,Giering, Warren P.
, p. 13 - 26 (2007/10/03)
Through the application of the quantitative analysis of ligand effects (QALE) method to the study of the hydrosilylation of acetophenone, we have shown, for the first time, that the initial rate and enantioselectivity of a complicated catalytic system responds in a rational manner to the variations in the stereoelectronic properties of the silane. The reactions (in benzene-d6 at 63 °C) were catalyzed by [Rh(cod)Cl]2/(chiral diphosphine) (chiral diphosphine=(R)-BINAP [(R)-(+)-2,2′-bis(diphenylphosphino)- 1,1′binaphthyl], (R,R)-tolyl-BINAP [(R)-(+)-2,2′-bis (di-p-tolylphosphino)-1,1′-binaphthyl], (R,R)-Me-DUPHOS [(R,R )-(-)-1,2-Bis-2,5-dimethylphospholano)benzene], (R,R)-DIOP [(R,R)-(-)-2,3-O-isopropylidine-2,3-dihydroxy-1,4-bis(diphenylphosphino) butane], and (R)-QUINAP [(R)-(+)-1-(2-diphenylphosphino-1-naphthyl) isoquinoline]. The ee's (R) of the hydrosilylation products (CH3CH(OSiR3)Ph) range between - 9 and 53% with the (R)-QUINAP giving the poorest enantioselectivity. The QALE analyses of log( R/S) for (R)-BINAP, (R)-tolyl-BINAP, (R,R)-Me-DUPHOS, and (R,R)-DIOP reveal that the steric effects associated with the silanes are not monotonic.
