25357-39-5Relevant academic research and scientific papers
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
, p. 12757 - 12760 (2020)
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
Silver-Promoted (4 + 1) Annulation of Isocyanoacetates with Alkylpyridinium Salts: Divergent Regioselective Synthesis of 1,2-Disubstituted Indolizines
Chen, Yan,Shatskiy, Andrey,Liu, Jian-Quan,K?rk?s, Markus D.,Wang, Xiang-Shan
supporting information, p. 7555 - 7560 (2021/10/02)
An unprecedented silver-promoted regioselective (4 + 1) annulation of isocyanoacetates with pyridinium salts is reported. The established protocol provides controlled, facile, and modular access to a range of synthetically useful N-fused heterocyclic scaffolds containing indolizines, pyrrolo[1,2-a]quinolines, pyrrolo[2,1-a]isoquinolines, and 1H-imidazo[4,5-a]indolizin-2(3H)-ones. A mechanistic pathway involving nucleophilic addition/protonation/elimination/cycloisomerization is proposed.
Ultrasound-promoted regioselective synthesis of chalcogeno-indolizines by a stepwise 1,3-dipolar cycloaddition
Vieira, Marcelo M.,Dalberto, Bianca T.,Coelho, Felipe L.,Schneider, Paulo H.
, (2020/07/03)
A series of new organochalcogen derivatives of indolizines was synthesized in moderate to excellent yields from pyridinium salts and chalcogeno-alkynes. The reaction can be carried out under thermal conditions or by sonochemical processes in short reaction times. The stepwise cycloaddition reaction forming chalcogeno-indolizines is regioselective and extends to a broad range of functional groups. Furthermore, novel chalcogeno-alkynes are reported and the first derivatives of teluro-indolizine are described. The influence of selenium functionalization on the photophysical properties of indolizines is also described, in which the compounds showed absorption in the UV–Vis region around 360 nm and emission in the blue-to-green region. Relatively low fluorescence quantum yield (?fl) values were calculated, in agreement with the chalcogen effect on other heterocycles.
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.
New substituted indolizines by 1,3-dipolar cycloaddition reactions. part 2. 7-cyanoindolizines
Dumitra?cu, Florea,Georgescu, Emilian,Georgescu, Florentina,Filip, Petru,Miu, Barbu,Dumitrescu, Dan G.
experimental part, p. 589 - 594 (2009/12/25)
The new indolizine derivatives 6a-e and 7a-e containing a cyano group grafted on the pyridinic ring were obtained by reaction of N-phenacylpyridinium bromides 3 with ethyl propiolate or l-butyn-3-one as acetylenic dipolarophiles in medium of 1,2-epoxypropane. Structural proof for the compounds was provided by elemental analysis and NMR spectroscopy, including COSY and HETCOR experiments.
Deprotonation of N-phenacyl- and N-acetonyl-4-cyanopyridinium halides with 1,4-diazabicyclo[2,2,2]octane
Szafran,Szwajca,??ska,Schroeder,Dega-Szafran
, p. 55 - 68 (2007/10/03)
In N-phenacyl- and N-acetonyl-4-cyanopyridinium halides (1a·Br and 1b·Cl) the N+CH2 hydrogens are replaced by deuterium in D20 or CH3OD solutions, similarly as in β-diketones, proving a prototropic equilibrium 1 = 2. The rate constants have been measured for deprotonation of 1a·Br and 1b·Cl with 1,4-diazabicyclo[2,2,2]octane (DABCO) in solutions. UV, FTIR, 1H and 13C NMR spectra are consistent with the ylide structure of the deprotonated species. N-phenacyl-4- cyanopyridinium ylide (3a) is relatively stable in the solid state and unstable in solutions. The observed parallel changes in ΔS ≠ and the time of disappearance of the ylide absorption band suggest that solvation is responsible for the ylide stability. The UV-Vis spectra of 1a·Br and 1b·Cl with DABCO show solvent dependent isosbestic points, which suggest that the decomposition reactions of ylides are very probably uniform. The PM3 and B3LYP calculations were carried out to investigate the structures of the cations, ylides and their complexes with ammonia and DABCO. Ylides are formed by abstraction of hydroxy proton from enol form (2) via complex 8.
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.
