6299-99-6Relevant academic research and scientific papers
Diversified Transformations of Tetrahydroindolizines to Construct Chiral 3-Arylindolizines and Dicarbofunctionalized 1,5-Diketones
Feng, Xiaoming,He, Qianwen,Liu, Xiaohua,Pan, Chenjing,Su, Zhishan,Wu, Zhikun,Zhang, Dong,Zhou, Yuqiao
supporting information, p. 15975 - 15985 (2020/10/18)
Enantioselective diverse synthesis of a small-molecule collection with structural and functional similarities or differences in an efficient manner is an appealing but formidable challenge. Asymmetric preparation and branching transformations of tetrahydroindolizines in succession present a useful approach to the construction of N-heterocycle-containing scaffolds with functional group, and stereochemical diversity. Herein, we report a breakthrough toward this end via an initial diastereo- A nd enantioselective [3 + 2] cycloaddition between pyridinium ylides and enones, following diversified sequential transformations. Chiral N,N′-dioxide-earth metal complexes enable the generation of optically active tetrahydroindolizines in situ, across the strong background reaction for racemate-formation. In connection with deliberate sequential transformations, involving convenient rearomatic oxidation, and light-active aza-Norrish II rearrangement, the tetrahydroindolizine intermediates were converted into the final library including 3-arylindolizine derivatives and dicarbofunctionalized 1,5-dicarbonyl compounds. More importantly, the stereochemistry of four-stereogenic centered tetrahydroindolizine intermediates could be efficiently transferred into axial chirality in 3-arylindolizines and vicinal pyridyl and aryl substituted 1,5-diketones. In addition, densely functionalized cyclopropanes and bridged cyclic compounds were also discovered depending on the nature of the pyridinium ylides. Mechanism studies were involved to explain the stereochemistry during the reaction processes.
Enantioselective dicarbofunctionalization of (: E)-alkenyloxindoles with pyridinium salts by chiral Lewis acid/photo relay catalysis
Zhang, Dong,Dong, Shunxi,He, Qianwen,Luo, Yao,Liu, Yun,Liu, Xiaohua,Feng, Xiaoming
supporting information, p. 12757 - 12760 (2020/11/02)
A highly efficient enantioselective dicarbofunctionalization reaction of (E)-alkenyloxindoles with pyridinium salts was realized. The process includes the chiral N,N′-dioxide-Sc(iii) complex-catalyzed regio-, diastereo-, and enantioselective [3+2] cycloaddition reaction and the following photo-promoted aza-Norrish II type rearrangement. A series of 2-pyridyl substituted oxindole derivatives were obtained in good yields with moderate to good diastereo- and enantioselectivities. This journal is
Facile one-pot tandem synthesis of perfluoroalkylated indolizines under metal-free mild conditions
He, Dong,Xu, Yuhong,Han, Jing,Deng, Hongmei,Shao, Min,Chen, Jie,Zhang, Hui,Cao, Weiguo
, p. 938 - 944 (2017/01/25)
A direct metal-free method for the synthesis of perfluoroalkylated indolizines by means of DIPEA-promoted tandem C[sbnd]N/C[sbnd]C bond formation was developed. Various substituted pyridines and bromoacetyl derivatives with methyl perfluoroalk-2-ynoates proceeded smoothly in this mild transformation, and the desired products were obtained in good to excellent yields under air.
Kinetics and Mechanism of the Pyridinolysis of Phenacyl Bromides in Acetonitrile
Koh, Han Joong,Han, Kwang Lae,Lee, Hai Whang,Lee, Ikchoon
, p. 4706 - 4711 (2007/10/03)
Kinetic studies of the reactions of substituted phenacyl bromides (YC6H4COCH2Br) with pyridines (XC5H4N) are carried out in acetonitrile at 45.0°C. A biphasic Bronsted plot is obtained with a change in slope from a large (βX ? 0.65-0.80) to a small (βX ? 0.36-0.40) value at pKao = 3.2-3.6, which can be attributed to a change in the rate-determining step from breakdown to formation of a tetrahedral intermediate in the reaction path as the basicity of the pyridine nucleophile increases. This mechanism is supported by the faster rates with pyridines than with anilines and the change of cross-interaction constant ρXY from a large positive (ρXY ? +1.4) to a small positive (ρXY ? +0.1) value. The large magnitude of Hammett ρX (= -5.5 to -6.9) values for the pyridines with electron-withdrawing substituents and positive deviations of the π-acceptors, p-CH3CO and p-CN, are quite similar to those for the pyridinium ion formation equilibria. The activation parameters are also in line with the proposed mechanism.
