Regioselective Addition of Silyl Enolates to α, β-Unsaturated Aldehyde and its Acetal Catalyzed by MgI2 Etherate

Regioselective addition reactions of silyl enolates to a, b-unsaturated aldehyde and its acetal catalyzed by MgI2 etherate give aldol adducts (1, 2-addition) preferentially over Michael adducts (1, 4-addition). This unique regioselectivity is distinctly different with other Lewis acidic promoters and may be attributed to the high oxyphilicity of IMg+.

经右心室电刺激致颤建立家兔心脏骤停模型

目的：建立一种简单、有效、稳定的家兔电刺激致颤心脏骤停（ CA）后脑复苏模型。方法选用20只新西兰雄性家兔，采用体表胸壁及心内膜下交流电诱发室颤的方法制作CA模型，CA 4 min后开始心肺复苏（CPR）。记录手术操作时间（TOP）、自主循环恢复时间（TROSC）、恢复率，除颤、肾上腺素次数，24 h、72 h存活率以及进行72 h大脑皮质凋亡细胞检测。另取10只兔为对照组，只进行致颤前手术操作。结果①20只家兔全部诱发CA成功，室颤发生率为100％。自主循环恢复率为80％；24 h、72 h存活率为50％、30％；除颤和肾上腺素次数为1．20±0.89、1．60±0．75；TOP和TROSC分别为（79±25）min、（268±33）s。②血浆神经元特异性烯醇化酶（NSE）水平显著升高，ROSC 72 h略有回降，但仍高于造模前（P＜0．05）。③与对照组比较，ROSC后72 h大脑皮质区出现了较多神经细胞的凋亡（P＜0．05）。④神经功能评分（NDS）在复苏后3 h时最低，以后渐趋好转。结论该模型操作简单、结果稳定、复苏成功率高，是一个较为理想的心肺脑复苏研究模型。

Regioselective 1,2-Addition of Ti(IV)-enolate to α, β–Unsaturated Compounds

The nucleophilic addition of Ti(IV) enolate derived from methyl aryl ketones to α, β–unsaturated compounds was found to be highly selective to give 1, 2 addition products.

Effect of SO_2 on the performance of Ag-Pd/Al_2O_3 for the selective catalytic reduction of NOx with C_2H_5OH

The influence of SO2 on the performance of Ag-Pd/Al2O3 for the selective catalytic reduction （SCR） of NOx with C2H5OH was investigated experimentally. The activity test results suggest that Ag-Pd/Al2O3 shows a small activity loss in the presence of SO2 when using C2H5OH as a reductant. In situ DRIFTS spectra show that the activity loss originates from the formation of surface sulphate species on the Ag-Pd/Al2O3. The surface sulphate species formation inhibits the formation of nitrate, whereas hardly changes the partial oxidation of C2H5OH. Compared with the NOx reduction by C3H6, an obvious suppression of the surface sulphate species formation was observed by DRIFTS experiment when using C2H5OH as a reductant. This phenomenon reveals the better catalytic performance and strong SO2 tolerance of Ag-Pd/Al2O3-C2H50H system.

Highly selective catalysts for the hydrogenation of alkynols:A review

The semi-hydrogenation of alkynols to enols is a crucial process in the production of pharmaceuticals,agrochemicals,fragrances,and flavors that involves a complex set of parallel and consecutive isomerization and hydrogenation reactions and proceeds via several key intermediates.In view of the industrial importance of large-scale enol production through alkynol hydrogenation,various noble and non-noble metal(e.g.,Ni and Pd)-based catalysts promoting this transformation have been developed.This paper reviews the design of highly selective catalysts for the semi-hydrogenation of alkynols,focusing on the role of additives,second metals,catalyst supports,and reaction conditions and combining catalytic reaction kinetics with theoretical calculations to establish the reaction mechanism and the decisive factors for boosting selectivity.Finally,a strategy for designing highly efficient and selective catalysts based on the characteristics of aqueous-phase alkynol hydrogenation is proposed.

In-situ generated ionic liquid catalyzed aldol condensation of trioxane with ester in mild homogeneous system

α, β-unsaturated esters were often synthesized from aldehydes and esters in the presence of strong organic base that was very sensitive to air and moisture via aldol reaction. Trioxane was very useful C1 resource, however, the decomposition of it was always the challenging problem that facing researchers. Herein, a novel synthetic methodology for α, β-unsaturated ester preparation from trioxane and ester with mild catalysis of generated ammonium trifluoromethanesulfonate ionic liquid. The enolization of ester as well as the decomposition of trioxane could proceed easily in the presence of boryl trifluoromethanesulfonate and amine at 20–25℃. Then the enolate and decomposed formaldehyde occurs aldol reaction to form α, β-unsaturated ester. With this strategy, the yield and selectivity of product from various substrates including aliphatic esters,lactones and thioester could reach up to 85.2% and 90.1%.

ENO1 expression and Erk phosphorylation in PDAC and their effects on tumor cell apoptosis in a hypoxic microenvironment

Objective: Hypoxia is an important feature of pancreatic ductal adenocarcinoma(PDAC). Previously, we found that hypoxia promotes ENO1 expression and PDAC invasion. However, the underlying molecular mechanism was remains unclear.Methods: The relationship between ENO1 expression and clinicopathological characteristics was analyzed in 84 patients with PADC. The effects of CoCl2-induced hypoxia and ENO1 downregulation on the apoptosis, invasion, and proliferation of PDAC cells were evaluated in vitro and in vivo. Hypoxia-and ENO1-induced gene expression was analyzed by transcriptomic sequencing.Results: The prognosis of PDAC with high ENO1 expression was poor(P < 0.05). High ENO1 expression was closely associated with histological differentiation and tumor invasion in 84 PDAC cases(P < 0.05). Hypoxia increased ENO1 expression in PDAC and promoted its migration and invasion. Apoptotic cells and the apoptosis marker caspase-3 in the CoCl_(2)-treated ENO1-sh group were significantly elevated(P < 0.05). Transcriptomic sequencing indicated that CoCl_(2)-induced PDAC cells initiated MAPK signaling. Under hypoxic conditions, PDAC cells upregulated ENO1 expression, thereby accelerating ERK phosphorylation and inhibiting apoptosis(P < 0.05). Consistent results were also observed in a PDAC-bearing mouse hindlimb ischemia model.Conclusions: Hypoxia-induced ENO1 expression promotes ERK phosphorylation and inhibits apoptosis, thus leading to PDAC survival and invasion. These results suggest that ENO1 is a potential therapeutic target for PDAC.

Zirconyl Chloride Promoted Highly Efficient Domino Synthesis of New 1, 2, 3, 4-Tetrahydroquinoline Derivatives in Water

The tetrahydroquinoline moiety is a structural feature of many natural products. By using a domino reaction of aromatic amines and cyclic enol ethers catalyzed by zirconyl chloride in water, various tetrahydroquinoline derivatives were synthesized efficiently. Most cyclized products showed cis selectivity. The cis selectivity was tentatively rationalized due to chelation control in water.

PMA-SiO_2 catalyzed synthesis of β-keto enol ethers

An efficient conversion of β-diketones into corresponding β-keto enol ethers with catalytic amount of PMA-SiO2 has been achieved.

A Novel Oscillating Chemical Reaction Using Ninhydrin as Single Organic Substrate

A novel oscillating chemical reaction using ninhydrin as a single organic substrate was represented in this paper. It distinguished from the classically catalyzed BZ oscillating chemical reaction due to there was no active methene （CH2=） and/or enol structure in the ninhydrin molecule, which served as single organic substrate. This suggested that the substrates used in catalyzed BZ reaction were not always the organic compounds containing active methene （CH2=） and/or enol structure and bromination process in this kind of catalyzed chemical oscillating reaction was not also necessary.

Synthesis and Crystal Structure of Arylbiscyclohexeneylmethane Derivatives

The title compound (p-methylphenylbis(4, 4-dimethyl-6-hydroxycyclohexene-1-one-2-yl)methane) has been synthesized by the reaction of 4-methylbenzaldehyde and 5, 5-dimethyl-1, 3-cyclohexanedione in N,N-dimethylformamide. Its structure was determined by single crystal X-ray diffraction. The Crystal is monoclinic, space group P21/a, a=0. 9304 (2)nm, b=1. 1754 (2)nm, c=2. 0134 (4)nm, β=102. 40(2)°, Mr= 382. 50, V=2. 1505 (7)nm3, Dc = 1. 181g/cm3, Z=4, μ(MoKα) = 0. 79cm-1, F(000) = 856.The structure was solved by direct methods, and refined by full-matris least-Squares method to a final R =0. 042 and Rw = 0. 045. The crystal structure shows that there are two conjugated enol form in the molecule.

Synthesis of 14-Bromo and 14-Hydroxy Baccatin III Derviatives

Several 14 alpha- and 14 beta -bromo baccatin III derivatives were synthesized by direct bromination and from silyl enol ether of 13-oxo-7-TES-baccatin III. 14 beta -Hyroxy baccatin III derivative was also obtained from the same silyl enol ether.

Two-water-assisted racemization of the succinimide intermediate formed in proteins. A computational model study

Racemization of aspartic acid (Asp) residues in proteins plays an important role in the molecular biology of aging. In the widely accepted mechanism of the Asp racemization, a succinimide (SI) intermediate is the species which actually undergo the direct racemization. In the present study, a two-water-assisted mechanism of the SI racemization was computationally investigated using a model compound in which an aminosuccinyl (Asu) residue is capped with acetyl and NMe groups on the N-and C-termini, respectively. The two water molecules catalyze the enolization of the Hα-Cα-C=O portion in the Asu residue by mediating proton relay from the α-carbon atom to the carboxyl oxygen atom. After the enolization, migration of the water molecules and conformational change lead to the mirror image of the initially formed enol two-water complex, and the racemization is completed by the following ketonization. The overall activation barrier (28.2 kcal·mol-1) corresponds to the enolization and ketonization steps, and falls within the available experimental activation energies (21.4-29.0 kcal·mol-1). Therefore, the two-water-assisted mechanism investigated here is plausible for the in vivo and in vitro racemization reactions of the SI intermediates formed in peptides and proteins.

A Novel Example of Hetero Diels-Alder Reaction

2, 3, 3a, 4, 5, 9b-hexahydro-8-(N-methylsulfamylmethyl)-4-phenylfuro[3, 2-c]quinoline was obtained when the alkylation of compound 1 was carried out with THF as solvent. The structure of the product was determined and the mechanism of the reaction was studied and proved by the imitation reaction.

Rhodium(Ⅲ)-catalyzed diastereo-and enantioselective hydrosilylation/cyclization reaction of cyclohexadienone-tetheredα,β-unsaturated aldehydes

A rhodium(Ⅲ)-catalyzed hydrosilylation/cyclization reaction of cyclohexadienone-tetheredα,β-unsaturated aldehydes(1,6-dienes)with triethylsilane is described,providing a series of cishydrobenzofurans,cis-hydroindoles,and cishydroindenes bearing silyl enol ether in good to excellent yields and excellent stereoselectivities.Additionally,the versatility of this method was demonstrated through a gram-scale experiment and various downstream transformations,highlighting its utility.

Catalytic Asymmetric[3+2]Cycloaddition of Exocyclic Enol Ethers for the Synthesis of Spiroketals

An efficient synthesis of chiral benzannulated spiroketals via catalytic asymmetric[3+2]cycloaddition of exocyclic enol ethers with p-quinones was achieved.The transformation was enabled by a chiral N,N′-dioxides/Tm^(Ⅲ)complex as the Lewis acid catalyst and afforded a series of enantiomerically enriched benzannulated spiroketal derivatives in good yields(up to 99%)and enantioselectivities(up to 98%ee).Topographic steric maps and distribution of the buried volumes of the catalysts via Cavallo’s SambVca 2 tool were used to elucidate the enantioinduction raised by the ligands and the metal ions.

Construction of Angularly Fused Tricyclic Compounds via Photo-induced Radical Cascade Cyclization

Photo-induced electron transfer (PET) of silyl enol ethers has been employed to synthesize several fused ring systems. However, the method has limited applicability due to its narrow substrate scope, low product yields, unsatisfactory stereo- and regioselectivity. Herein, we report a PET-triggered cascade reaction of silyl enolates that leads to the formation of angularly fused tricyclic scaffolds. The reaction exhibits broad substrate scope and excellent stereoselectivity. The regio- and stereoselectivity of this cascade reaction is elucidated via DFT calculation and conformational analysis.

Chiral nickel(Ⅱ) complex catalyzed asymmetric(3+2) cycloaddition ofα-diazo pyrazoleamides with 2-siloxy-1-alkenes

A highly efficient asymmetric(3 + 2) cycloaddition of α-diazo pyrazoleamides with silyl enol ethers was realized by employing a chiral N,N’-dioxide-Ni(II) complex catalyst. The process includes the formation of chiral nickel carbenoid intermediate and the following enantioselective cycloaddition reaction. The desired dihydrofuran O,O-acetal derivatives were obtained in good yields(up to 90%) with high enantioselectivity(up to 99% ee) under mild reaction conditions within short reaction time. On the basis of the determination of the catalyst structure, a possible transition state mode was proposed.

Excited-State Palladium-Catalyzed α-Selective C1-Ketonylation

C-Glycosides are important carbohydrate mimetics found in natural products,bioactive compounds,and marketed drugs.However,stereoselective preparation of this class of glycomimetics remains a significant challenge in organic synthesis.Herein,we report an excited-state palladium-catalyzedα-selective C-ketonylation synthetic strategy using readily available 1-bromosugars to access a range of C-glycosides.The reaction featured excellentα-selectivity and mild conditions that tolerated a wide range of functional groups and complex molecular architectures.The resultingα-ketonylsugars could serve as versatile precursors for theirβ-isomers and other C-glycosides.Preliminary experimental and computational studies of the mechanism suggested a radical pathway involving the formation of palladoradical and glycosyl radical that undergoes polarity-mismatched coupling with silyl enol ether,affording the desiredα-ketonylsugars.Insight into the reactivity and mechanism will inspire a new reaction development and provide straightforward access to bothα-andβ-C-glycosides,thereby greatly expanding the chemical and patent spaces of glycomimetics.