25357-46-4Relevant 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.
Copper acetate monohydrate: A cheap but efficient oxidant for synthesizing multi-substituted indolizines from pyridinium ylides and electron deficient alkenes
Hu, Huayou,Feng, Junjun,Zhu, Yulan,Gu, Ning,Kan, Yuhe
, p. 8637 - 8644 (2015/02/19)
We report a highly practical one-pot method for synthesizing multi-substituted indolizines from ?±-halide carbonyl compounds, pyridines and electron deficient alkenes in the presence of copper acetate monohydrate and sodium acetate in DMF. A variety of function groups are tolerable in standard reaction conditions, including aldehyde. 36 examples were presented. The yield of indolizine was from moderate to high. Furthermore, multi-substituted indolizines can be prepared at gram scale by this method.
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.
Kinetics of Reaction of Phenacyl Bromide with 3- and 4-Substituted Pyridines and 4-Substituted 4-Styrylpyridines
Shunmugasundaram, A.,Balakumar, S.
, p. 775 - 777 (2007/10/02)
The rates of reaction of phenacyl bromide with 3- and 4-substituted pyridines and 4'-substituted 4-styrylpyridines have been measured in aq. acetone (90percent, v/v) at 30 deg C, 35 deg C and 40 deg C and the activation parameters have been evaluated.Satisfactory Hammett correlations are obtained for both pyridine and styrylpyridine series.The effectiveness of transmission of substituent effect in styrylpyridine system relative to pyridine system in this reaction is calculated to be 0.104.From the Bronsted relationship the coefficient (βN) is found to be 0.48, indicating that the extent of bond formation in the transition state is moderate.
