30407-41-1Relevant articles and documents
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McElrath,E.N. et al.
, p. 2195 - 2200 (1960)
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Understanding reactivity and stereoselectivity in palladium-catalyzed diastereoselective sp3 C-H Bond activation: Intermediate characterization and computational studies
Giri, Ramesh,Lan, Yu,Liu, Peng,Houk,Yu, Jin-Quan
, p. 14118 - 14126 (2012)
The origin of the high levels of reactivity and diastereoselectivity (>99:1 dr) observed in the oxazoline-directed, Pd(II)-catalyzed sp 3 C-H bond iodination and acetoxylation reactions as reported in previous publications has been studied and explained on the basis of experimental and computational investigations. The characterization of a trinuclear chiral C-H insertion intermediate by X-ray paved the way for further investigations into C-H insertion step through the lens of stereochemistry. Computational investigations on reactivities and diastereoselectivities of C-H activation of t-Bu- and i-Pr-substituted oxazolines provided good agreement with the experimental results. Theoretical predictions with DFT calculations revealed that C-H activation occurs at the monomeric Pd center and that the most preferred transition state for C-H activation contains two sterically bulky t-Bu substituents in anti-positions due to steric repulsion and that this transition state leads to the major diastereomer, which is consistent with the structure of the newly characterized C-H insertion intermediate. The structural information about the transition state also suggests that a minimum dihedral angle between C-H bonds and Pd-OAc bonds is crucial for C-H bond cleavage. We have also utilized density functional theory (DFT) to calculate the energies of various potential intermediates and transition states with t-Bu- and i-Pr-substituted oxazolines and suggested a possible explanation for the substantial difference in reactivity between the t-Bu- and i-Pr-substituted oxazolines.
CATALYTICS ASYMMETRIC ACTIVATION OF UNACTIVATED C-H BONDS, AND COMPOUNDS RELATED THERETO
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Page/Page column 76-77; 89-90, (2010/10/20)
One aspect of the present invention is directed in part to catalytic and stereoselective functionalization of unactivated C-H bonds of simple organic substrates. The compounds and methods provided herein allow one to control the stereochemistry in a C-H activation step, activate substrates containing α-hydrogens next to the directing group, and remove a directing group under mild conditions. One aspect of the present invention relates to a transition-metal-catalyzed method for selective and asymmetric oxidation of carbons located in a β- or γ-position relative to an auxiliary. Another aspect of the invention relates to the enantiomerically-enriched substrates and the enantiomerically-enriched products formed via said method. In certain embodiments, oxazoline and oxazinone directing groups are used. In addition, the Boc protecting group has been identified as a directing group which does not necessitate removal.
