title: Highly Enantioselective Allylic C-H Alkylation of Terminal Olefins with Pyrazol-5-ones Enabled by Cooperative Catalysis of Palladium Complex and Brønsted Acid.
abstract: A highly enantioselective allylic C-H alkylation reaction of allylarenes with pyrazol-5-ones has been established by the cooperative catalysis of a chiral palladium complex and chiral Brønsted acid to afford a wide spectrum of functionalized chiral N-heterocycles with an all-carbon quaternary stereogenic center in high yields and with high levels of enantioselectivity (up to 96% ee), wherein the chiral ligand and phosphoric acid showed synergistic effect on the control of stereoselectivity. In addition, a palladium-catalyzed asymmetric allylic C-H alkylation of 1,4-pentadienes with pyrazol-5-ones has been realized to furnish highly functionalized pyrazol-5-ones in high enantioselectivities. In this case, the chiral ligand controls the stereoselectivity while the achiral Bronsted acid, 2-fluorobenzoic acid, turns out to be a better cocatalyst than the chiral phosphoric acid. The installation of electron-deficient substituents at 3,3'-positions of binaphthyl backbone of chiral phosphoramidites is actually beneficial to the allylic C-H oxidation due to their survival in the presence of quinone derivative oxidants. These allylic C-H alkylation reactions undergo smoothly under mild conditions and tolerate a wide range of substrates. The resultant highly functionalized chiral pyrazol-5-ones have been applied to the preparation of more structurally diverse heterocycles by classical transformations.
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.
authors.forename: Hua-Chen
authors.initials: HC
authors.lastname: Lin
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.
authors.forename: Pu-Sheng
authors.initials: PS
authors.lastname: Wang
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.
authors.forename: Zhong-Lin
authors.initials: ZL
authors.lastname: Tao
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.
authors.forename: Yu-Gen
authors.initials: YG
authors.lastname: Chen
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.
authors.forename: Zhi-Yong
authors.initials: ZY
authors.lastname: Han
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.|Collaborative Innovation Center of Chemical Science and Engineering , Tianjin, China.
authors.forename: Liu-Zhu
authors.initials: LZ
authors.lastname: Gong