78191-65-8Relevant academic research and scientific papers
Application of Trimethylgermanyl-Substituted Bisphosphine Ligands with Enhanced Dispersion Interactions to Copper-Catalyzed Hydroboration of Disubstituted Alkenes
Xi, Yumeng,Su, Bo,Qi, Xiaotian,Pedram, Shayun,Liu, Peng,Hartwig, John F.
, p. 18213 - 18222 (2020/12/04)
We report the incorporation of large substituents based on heavy main-group elements that are atypical in ligand architectures to enhance dispersion interactions and, thereby, enhance enantioselectivity. Specifically, we prepared the chiral biaryl bisphosphine ligand (TMG-SYNPHOS) containing 3,5-bis(trimethylgermanyl)phenyl groups on phosphorus and applied this ligand to the challenging problem of enantioselective hydrofunctionalization reactions of 1,1-disubtituted alkenes. Indeed, TMG-SYNPHOS forms a copper complex that catalyzes hydroboration of 1,1-disubtituted alkenes with high levels of enantioselectivity, even when the two substituents are both primary alkyl groups. In addition, copper catalysts bearing ligands possessing germanyl groups were much more active for hydroboration than one derived from DTBM-SEGPHOS, a ligand containing 3,5-di-tert-butyl groups and widely used for copper-catalyzed hydrofunctionalization. This observation led to the identification of DTMGM-SEGPHOS, a bisphosphine ligand bearing 3,5-bis(trimethylgermanyl)-4-methoxyphenyl groups as the substituents on the phosphorus, as a new ligand that forms a highly active catalyst for hydroboration of unactivated 1,2-disubstituted alkenes, a class of substrates that has not readily undergone copper-catalyzed hydroboration previously. Computational studies revealed that the enantioselectivity and catalytic efficiency of the germanyl-substituted ligands is higher than that of the silyl and tert-butyl-substituted analogues because of attractive dispersion interactions between the bulky trimethylgermanyl groups on the ancillary ligand and the alkene substrate and that Pauli repulsive interactions tended to decrease enantioselectivity.
Mechanistic study of the titanocene(III)-catalyzed radical arylation of epoxides
Gans?uer, Andreas,Von Laufenberg, Daniel,Kube, Christian,Dahmen, Tobias,Michelmann, Antonius,Behlendorf, Maike,Sure, Rebecca,Seddiqzai, Meriam,Grimme, Stefan,Sadasivam, Dhandapani V.,Fianu, Godfred D.,Flowers, Robert A.
, p. 280 - 289 (2015/08/19)
An atom-economical and catalytic arylation of epoxide-derived radicals is described. The key step of the catalytic system is a sequential electron and proton transfer for the rearomatization of the radical σ-complex and catalyst regeneration. Kinetic, computational, spectroscopic, and cyclo-voltammetric investigations highlight the key issues of the reaction mechanism and catalyst stabilization by collidine hydrochloride. Studies employing radicophiles rule out the participation of cations as reactive intermediates.
HYDROBORATION D'AMINES ALLYLIQUES. REACTIVITE DES ORGANOBORANES
Baboulene, Michel,Torregrosa, Jean-Luc,Speziale, Vincent,Lattes, Armand
, p. 565 - 570 (2007/10/02)
Hydroboration of differently substituted allylic amines has been studied systematically.It was possible to demonstrate the importance of the hydroboration agent on the formation of aminoboranes.Oxidation of aminoboranes by hydrogen peroxyde in basic medium has ben examined and has led, with good yields, to primary aminoalcohols or a mixture of isomeric aminoalcohols.The influence of steric hindrance on the double bond and that of substitution of the nitrogen atom have been shown.
