73773-15-6Relevant academic research and scientific papers
Enantioselective Diarylcarbene Insertion into Si-H Bonds Induced by Electronic Properties of the Carbenes
Evans, Declan,Houk, K. N.,Li, Mao-Lin,Li, Wen-Tao,Xu, Bin,Yang, Liang-Liang,Zhou, Qi-Lin,Zhu, Shou-Fei
, p. 12394 - 12399 (2020/08/06)
Catalytic enantioselection usually depends on differences in steric interactions between prochiral substrates and a chiral catalyst. We have discovered a carbene Si-H insertion in which the enantioselectivity depends primarily on the electronic characteristics of the carbene substrate, and the log(er) values are linearly related to Hammett parameters. A new class of chiral tetraphosphate dirhodium catalysts was developed; it shows excellent activity and enantioselectivity for the insertion of diarylcarbenes into the Si-H bond of silanes. Computational and mechanistic studies show how the electronic differences between the two aryls of the carbene lead to differences in energies of the diastereomeric transition states. This study provides a new strategy for asymmetric catalysis exploiting the electronic properties of the substrates.
Asymmetric additive-free aryl addition to aldehydes using perhydrobenzoxazines as ligands and boroxins as aryl source
Infante, Rebeca,Nieto, Javier,Andres, Celia
experimental part, p. 6691 - 6699 (2011/11/04)
A highly efficient enantioselective aryl addition to aldehydes using boroxins as aryl source and conformationally restricted perhydro-1,3- benzoxazines as ligands is reported. Both enantiomeric forms of chiral arylphenylmethanols and 1,1′-disubstituted diarylmethanols are afforded with excellent yields and enantioselectivities using the same ligand by means of an appropriate combination of boroxin and aromatic aldehyde. The enantiocontrol is not significantly influenced by electronic effects or steric hindrance, even with substituted boroxins. Very homogeneous ee's are reached when substituted arylboroxins are employed, without the use of any class of additive or pre-treatment.
Practical implications of boron-to-zinc transmetalation for the catalytic asymmetric arylation of aldehydes
Jimeno, Ciril,Sayalero, Sonia,Fjermestad, Torstein,Colet, Gisela,Maseras, Feliu,Pericas, Miquel A.
, p. 1098 - 1101 (2008/09/20)
(Chemical Equation Presented) Faster than believed: Transmetalation from aryl boronic acids and triaryl boroxines to diethylzinc takes place within minutes following a two-step, low-energy pathway (see picture), according to density functional calculations and reaction microcalorimetry measurements. The experimental conditions for a practical, atom-economical, and highly enantioselective catalytic arylation of a variety of aldehydes have been developed from these data.
