Mechanism and Enantioselectivity in Palladium-Catalyzed Conjugate Addition of Arylboronic Acids to 闁?Substituted Cyclic Enones: Insights from Computation and Experiment was written by Holder, Jeffrey C.;Zou, Lufeng;Marziale, Alexander N.;Liu, Peng;Lan, Yu;Gatti, Michele;Kikushima, Kotaro;Houk, K. N.;Stoltz, Brian M.. And the article was included in Journal of the American Chemical Society in 2013.Name: (S)-4-(tert-Butyl)-2-(4-(trifluoromethyl)pyridin-2-yl)-4,5-dihydrooxazole This article mentions the following:
Enantioselective conjugate additions of arylboronic acids to 闁?substituted cyclic enones have been previously reported from our laboratories Air- and moisture-tolerant conditions were achieved with a catalyst derived in situ from palladium-(II) trifluoroacetate and the chiral ligand (S)-t-BuPyOx. We now report a combined exptl. and computational investigation on the mechanism, the nature of the active catalyst, the origins of the enantioselectivity, and the stereoelectronic effects of the ligand and the substrates of this transformation. Enantioselectivity is controlled primarily by steric repulsions between the t-Bu group of the chiral ligand and the 婵?methylene hydrogens of the enone substrate in the enantio-determining carbopalladation step. Computations indicate that the reaction occurs via formation of a cationic arylpalladium-(II) species, and subsequent carbopalladation of the enone olefin forms the key carbon-carbon bond. Studies of nonlinear effects and stoichiometric and catalytic reactions of isolated (PyOx)-Pd-(Ph)I complexes show that a monomeric arylpalladium-ligand complex is the active species in the selectivity-determining step. The addition of water and ammonium hexafluorophosphate synergistically increases the rate of the reaction, corroborating the hypothesis that a cationic palladium species is involved in the reaction pathway. These additives also allow the reaction to be performed at 40 闂佺娅ｉ悡?and facilitate an expanded substrate scope. In the experiment, the researchers used many compounds, for example, (S)-4-(tert-Butyl)-2-(4-(trifluoromethyl)pyridin-2-yl)-4,5-dihydrooxazole (cas: 1257527-14-2Name: (S)-4-(tert-Butyl)-2-(4-(trifluoromethyl)pyridin-2-yl)-4,5-dihydrooxazole).
(S)-4-(tert-Butyl)-2-(4-(trifluoromethyl)pyridin-2-yl)-4,5-dihydrooxazole (cas: 1257527-14-2) belongs to pyridine derivatives. Pyridine is diamagnetic and has a diamagnetic susceptibility of 闂?8.7 闂?10闂? cm3闁荤姾娅ｅΛ纭俵闂?.The molecular electric dipole moment is 2.2 debyes. The standard enthalpy of formation is 100.2 kJ闁荤姾娅ｅΛ纭俵闂? in the liquid phase and 140.4 kJ闁荤姾娅ｅΛ纭俵闂? in the gas phase. Halopyridines are particularly attractive synthetic building blocks in a variety of cross-coupling methods, including the Suzuki-Miyaura cross-coupling reaction.Name: (S)-4-(tert-Butyl)-2-(4-(trifluoromethyl)pyridin-2-yl)-4,5-dihydrooxazole