Synthesis of oxapenem derivatives by novel reductive cyclization

Several 6-ethyl-substituted l-oxapenem derivatives were synthesized by the application of the established method. Furthermore novel and effective synthesis of oxapenems $\text{via}$ reductive cyclization of 2-chloro-2-(4-chloro-3-ethyl-2-oxo-l-azetidinyl) acetoacetates ($\text{1}$$\text{0}$) using sodium thiolates is reported.     

Synthesis of 5-substituted-1H-indol-2-yl-1H-quinolin-2-ones: a novel class of KDR kinase inhibitors

[reaction: see text] A number of approaches for the synthesis of the 1H-indol-2-yl-1H-quinolin-2-one ring system found in the potent and selective KDR kinase inhibitor 1 are described. The preparation and reaction of trimethylsilylnitrobenzene 26 with 2-methoxy-3-quinolinecarboxaldehyde 28 afforded alcohol 30, which was the key intermediate for the preparation of the target compounds. Conversion of alcohol 30 to either nitroketone 36 or nitrostyrene 45 set the stage for reductive cyclization and the formation of indole 25. The quinolin-2-one functionality was unmasked in the last step to provide compound 1 in 56-60% overall yield from readily available starting materials.     

Synthesis of novel N-hydroxy heterocycles via intramolecular reductive cyclization of diketoximes by NaBH3CN

A simple and efficient protocol for the construction of substituted piperazines, piperidines, thiomorpholines, decahydroquinolines, perhydrocyclopenta[b]pyridine, and pyrrolidines bearing N-hydroxy substituents through intramolecular reductive cyclization of diketoximes using sodium cyanoborohydride is described.     

Synthesis of macrocyclic esters by catalytic cyclization

Macrocyclic esters were synthesized in good yield through catalytic cyclization by metal salts of glycol monosuccinates. The procedure is an improvement over catalytic depolymerization for the preparation of cyclic compounds, as developed by Carothers.     

Synthesis of heterocycles via ligand-free palladium catalyzed reductive Heck cyclization

Synthesis of five and six membered heterocycles, indolines, 2,3-dihydrobenzofurans, chromans, isochromans, 1,2,3,4-tetrahydroquinolines, and 1,2,3,4-tetrahydroisoquinolines, in 70-99% yield by a ligand-free palladium catalyzed reductive Heck cyclization of phenyl bromides and chlorides, under mild conditions, is reported. Water was found to be essential for these reactions.     

Synthesis of a new siladigermirane via an intramolecular reductive cyclization

Si,Si-diphenyltetramesitylsiladigermirane was synthesized via the intramolecular reductive cyclization of bis(chlorodimesitylgermyl)diphenylsilane using t-BuLi or Rieke magnesium. Addition of water to the siladigermirane resulted in regioselective hydrolysis of the siladigermirane to give 1-(hydroxydiphenylsilyl)-1,1,2,2-tetramesityldigermane.     

Nickel-catalyzed reductive cyclization of organohalides

A mild and convenient nickel-catalyzed method for free-radical cyclization of organohalides is described. The use of a NiCl(2)?DME/Pybox complex as the catalyst and zinc powder in methanol efficiently promotes the reductive cyclization of various unsaturated alkyl halides to give carbo-, oxa-, and azacycles as products in high yields.     

Synthesis of the spirofungin B core by a reductive cyclization strategy

[reaction: see text] A reductive decyanation approach to the synthesis of the core of spirofungin B has been developed. Spirofungin B has only one anomeric stabilization in the spiroacetal and was isolated along with its spiroacetal epimer, spirofungin A. The cyclization precursor was constructed from readily available starting materials. The reductive cyclization reaction was both efficient and stereoselective. The reductive cyclization strategy to spiroacetals is convergent and effective.     

Synthesis of novel 3,4-diaryl-5-aminopyrazoles as potential kinase inhibitors

Synthesis of a diverse series of novel 3,4-diaryl-5-aminopyrazoles as candidates in the development of new protein kinase inhibitors is reported for the first time. In the course of a wider study into bisindolylmaleimide (BIM) derivatives, we examined a novel 5-aminopyrazole heterocyclic moiety as a structural analogue of the highly potent VEGF-R2/3 inhibitor pyrrole-2-one (8). The versatile nature of this pharmacophore allows considerable scope for derivatisation and hence exploration of structure activity relationships. Consequently, a variety of structural modifications were used in order to diversify the aminopyrazole ring substituents. Bicyclic derivatives of the parent aminopyrazoles (11, 12) were also synthesised as a means of probing the kinase active site, leading to formation of complex planar pyrimidine moieties. This work provides the framework for new explorations into kinase inhibition and critical investigations into selectivity of inhibitory activity.     

基于γ-环糊精的谷胱甘肽过氧化物酶模拟物的构建及催化作用

基于对天然谷胱甘肽过氧化物酶(GPX)结构与功能的理解,我们利用超分子化学的方法和原理,选择γ-环糊精为骨架,通过引入催化基团硒或碲,设计并合成了7种基于γ-环糊精的新型谷胱甘肽过氧化物酶(GPX)模拟物,并采用元素分析、红外光谱、核磁共振等手段对其结构进行了详细的表征和确认。运用GPX经典双酶体系法测定了它们的GPX活性,实验结果表明:6,6’双碲桥联γ-环糊精(6-diTe-γ-CD)表现出了最高的GPX活性,其催化GSH还原过氧化氢(H2O2)、叔丁基过氧化氢(t-BuOOH)和枯烯过氧化氢(CuOOH)的活力分别是传统小分子硒酶Ebselen的147.3、1897.9和663.9倍,该结果是目前报道的环糊精GPX模拟物中酶活力最高的。     

Iron-catalyzed reductive cyclization of nitroarenes: Synthesis of aza-heterocycles and DFT calculations

Research into environmentally friendly strategies for hydrogen transfer reduction is increasing, along with the need for more elaborate heterocyclic platforms. Within this context, we develop a new approach for substituted dihydrobenzo[c]carbazoles and indoles. These compounds were synthesized through an iron-catalyzed hydrogen transfer reduction of nitroarenes, followed by intramolecular cyclization. This transformation involves using a Knölker-type catalyst, Cs₂CO₃ as the base, and benzyl alcohol as the non-expensive and low volatile hydrogen donor. We synthesize 30 examples of aza-heterocycles with moderate to excellent yields by applying this strategy. Additionally, DFT calculations demonstrated that the pathway reaction could follow an anionic mechanism.     

A straightforward approach to N-substituted-2H-indazol-2-amines through reductive cyclization

A versatile two-step, one-pot reaction to access N-substituted-2H-indazol-2-amine derivatives has been elaborated. A diverse set of analogues was obtained by a sequential hydrazone formation and reductive cyclization in moderate to good yields from readily available starting materials. The strategy tolerates a broad range of substitutions pattern and functional groups allowing further derivatizations.     

A general method for the catalytic nazarov cyclization of heteroaromatic compounds

A general, catalytic method for efficient Nazarov cyclization of systems containing heteroaromatic components has been developed. Scandium triflate was identified as the most reactive promoter, and it was found that addition of lithium perchlorate was necessary for synthetically useful catalytic cyclizations. The method was used to synthesize a range of cyclopentanone-fused heteroaromatic systems in 36-97% yield, and the reactivity trends observed demonstrate the impact of polarization on cyclization efficiency. [reaction: see text].     

Synthesis of 3-substituted quinolines via transition-metal-catalyzed reductive cyclization of o-nitro Baylis-Hillman acetates

Reductive cyclization of o-nitro-substituted Baylis-Hillman acetates by carbon monoxide, catalyzed by [CpFe(CO)(2)](2), gives moderate to good yields of 3-substituted quinolines.     

Synthesis of substituted pyrazolo[1,5-a]quinoxalines using the reductive cyclization

Russian Chemical Bulletin - New pyrazolo[1,5-a]quinoxalin-4-ones were obtained by reductive cyclization from the corresponding 1-(2-nitroaryl)pyrazole-5-carboxylates. Alternatively,...     

Synthesis of novel macrocyclic ether-ester compounds via the intramolecular cyclization of oligoethylene glycol monocarboxymethyl ethers.

By treating of the oligoethylene glycol monocarboxymethyl ethers with p-toluenesulfonyl chloride in the presence of alkali metal carbonates, novel macrocyclic polyether-monoester compounds were obtained in moderate yield.