[Bmim]Br_3 as a New Reagent for Regioselective Mono-bromination of Activated Aromatics under Solvent-free Conditions

Reaction of activated aromatics containing phenobs, naphthol, methoxynaphthalenes,anisole etc. with 1-butyl-3-methylimidazolium tribromide （[Bmim]Br3） under solvent-free conditions, selectively gave the corresponding monobromination products with excellent yields.

An efficient chemo-and regioselective three-component synthesis of pyridazinones and phthalazinones using activated KSF

The first three-component and regioselective synthesis of pyridazinones and phthalazinones from arenes,anhydrides and ArNHNH;in the presence of efficient recyclable heterogeneous catalyst,montmorillonite-KSF,in high yield and short reaction time is reported.

Regioselective Bromination of 3, 4-Dimethoxytoluene with N-Bromosuccinimide

The selective brominations of 3, 4-dimethoxytoluene with N-bromosuccinimide were reported. The nuclear and side-chain brominated products were obtained under different reaction conditions. The mechanism was also discussed.

Preparation of Cellulose Nanofibrils by Multi-Site Regioselective Oxidation

Cellulose nanofibrils(CNFs)are promising sustainable materials that can be applied to nanocomposites,as well as medical and life-sciences devices.However,methods for the preparation of these important materials are energy intensive because heating and mechanical disintegration are required to produce cellulose fibers below 100 nm in size.In this study,CNFs were prepared through the multi-site regioselective oxidation of cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO)and periodate at room temperature(20–25°C),without any mechanical-disintegration treatment.Transmission electron microscopy(TEM)revealed that the CNFs had the average widths of 14.1,55.4,and 81.9 nm for three different treatments.Fourier-transform infrared spectroscopy revealed that carboxyl groups were created on the surfaces of the microfibrils,while X-ray diffraction studies showed that the cellulose I structure was maintained after oxidation,and that the cellulose nanofibril crystallinity index exceeded 70%.These results demonstrate that CNFs can be prepared by multi-site regioselective oxidation at room temperature in the absence of mechanical disintegration.In addition,a model was developed to calculate the total content of carboxylate and aldehyde groups of CNFs prepared by the TEMPO mediate oxidation,the periodate oxidation,and the multi-site regioselective oxidation methods based on the particle width determined by TEM.The calculated values of the model were in good agreement with the total content(experimental value)of carboxylate and aldehyde groups of CNFs prepared by the TEMPO-mediated oxidation and the multi-site regioselective oxidation methods.However,the model was not valid for CNFs prepared by the periodate oxidation method.

Synthesis of kanamycin A derivatives by regioselective masking drug resistant enzymes targeting hydroxyl groups

The 3＇-OH, 4＇-OH and 2＂-OH of kanamycin A were modified in search of new aminoglycosides to overcome resistant enzymes, ANTs and APHs. The key intermediate was a dibenzylidene-protected derivative of kanamycin A. The aimed sites were masked by benzyl, methyl and allyl groups. Multi-step reactions gave the desired aminoglycoside derivatives but showed less antibiotic activity than kanamycin A.

Regioselective and Stereoselective Synthesis of the 3-Aryl-4- phosphoryl-1, 2, 4-triazoline-5-ones

A novel and efficient route of synthesizing 1, 2, 4-triazoline-5-ones is reported. The title compounds can be prepared in high yield and purity by the one-pot oxidation and cyclization of 1-acylthiosemicarbazides. The reaction is regioselective and stereoselective. The reaction condition is mild.

Synthesize of 2,6-Di-O-acetyl Sucrose by Regioselective Acetylation with Dibutyltin Oxide

Di-O-acetyl sucrose was regioselective synthesized by using dibutyltin oxide in about 60% yield. The structure of acetyl derivative was elucidated by 1H NMR, 13C NMR, 2D-NMR and MS spectral data.

Regioselective protection of 10-deacetylbaccatin Ⅲ and semi-synthesis of paclitaxel

Semi-synthesis of paclitaxel was achieved in four steps from 10-deacetylbaccatin HI （10-DAB HI）. The key steps are the regioselective protection at the hydroxyl group at C-7 of 10-DAB HI, using 1,1′-thiocarbonyldiimidazole as a selective reagent, and the deprotection of the protected paclitaxel with a mixture of p-toluenesulfonic acid and 0.1 mol/L aqueous hydrochloride.

Regioselective Decomposition of 11-Substituted-16α,17α- methyleneazopregna-1,4-dien-3,20-dione

Regioselective decomposition of 11-substituted- 16α, 17α-methyleneazopregna- 1,4-dien- 3, 20-dione Ⅰ proceeded smoothly through thermal decomposition in the presence of BF3·Et2O or HClO4 with high yields. Ⅰ was converted to 11-substituted-16-methylpregna-1, 4, 16（17）-trien-3, 20-dione Ⅱ by the thermal decomposition, while with HClO4 ad a catalyst, 11-substituted-16α, 17α-methylenepregna-1, 4-dien-3, 20-dione Ⅲ was the main product. However, when BF3·Et2O was used as catalyst, a mixture of Ⅱ and Ⅲ（1 ： 3） was obtained.

THE REGIOSELECTIVE SYNTHESIS OF NOVEL PHENYLSULFONES BEARING ISOPRENE UNITS

The facile and regioselective synthesis of some novel phenylsulfones bearing isoprene units were accomplished by using the corresponding terpenoid compounds as the starting material through ene-chlorination and phenylsulfonyl group substritution steps. The yields are excellent and the experimental conditions are very mild.

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+.

Regioselective Synthesis, Crystal Structure and Biological Activity of Novel 2-Phenylsulfonylhydrazono-3-(3-trifluoromethylphenyl)-2(3H)-thiazoline Derivatives

The title compounds 2-phenylsulfonylhydrazono-3-（3-trifluoromethylphenyl）-2（3H）- thiazoline derivatives were designed and synthesized via the reaction of thiosemicarbazides with chloroacetaldehyde, and their chemical structures were characterized by ^1H NMR, ^13C NMR, elemental analysis and MS. Furthermore, 4a was characterized by single-crystal X-ray diffraction. The target compound 4a （C16H12F3N302S2, Mr = 399.41） crystallized in monoclinic system, P21/c space group with a = 7.7457（4）, b = 13.5850（7）, c = 16.5455（10） A, β= 99.698（2）°, V= 1656.30（16） A3, Dc = 1.602 g/cm^3, Z = 4, F（000） = 816, λ = 0.71070 A,μ（MoKa） = 0.370 mm^-1, R = 0.072 and wR = 0.0867. The crystal structure of 4a revealed the cyclization of thiosemicarbazide moiety with chloroacetaldehyde at the N（l） position. The title compounds exhibited good insecticidal activity against spider mite （Tetranychus cinnabarinus Boisduval） and favorable fungicidal activity against Corynespora cassiicola.

The Synthesis and Regioselective Hydrolysis of Dialkyl 2-Phenylfuran (and 2-Phenyltetrahydrofuran) -3,4-dicarboxylates

Dialkyl 2-phenylfuran (and 2-phenyltetrahydrofuran)-3,4-dicarboxylates (1, 2, 5-7), which are potential precursors of the synthesis of furofuran and tetrahydrofurofuran lignans, can be selectively hydrolyzed to monoacid (3, 8) by potassium hydroxide. The regioselective hydrolysis was affected significantly by the 2-phenyl group of the furan or tetrahydrofuran skeleton. The geometric structures of 3, 8 and related compounds were elucidated and verified by NMR spectra.

REGIOSELECTIVE ALLYLATION OF THE TERMINAL EPOXIDES BY ALLYL BROMIDE AND METALLIC ZINC OR TIN

Allylation of terminal epoxides(1)to give the homoallylic alcohols(2)and bishomoallylic alcohols(3)can be carried out successfully by allyl bromide and metallic zinc or tin.The effect of substituents on epoxides was studied.

REGIOSELECTIVE O-ALKYLATION OF MYO-INOSITOL DERIV ATIVES WITH ALKYL HALIDES UNDER S-L PHASE TRANSFER CATALYTIC CONDITIONS

A convenient synthetic approach leading to protected inositol was described based on regioselective O-alkylation using alkyl halide under solid-liquid PTC condition

REGIOSELECTIVE OXIDATION OF KETONE BY AN OXIDATIVE REAGENT SYSTEM KH/O_2/18-CROWN-6/THF:APPLICATION TO SYNTHESIS OF VARIOUS LACTONES

the regioselectivity in the oxidation of different types of ketone compounds 1--6 with an oxidative reagent system,KH/O_2/18- Crown-6/THF is described.From these oxidative products,the various lactones have been prepared.

HIGHLY REGIOSELECTIVE O-AND N-ACYLATION OF 5-METHYL-3-HYDROXYISOXAZOLE

Acylation of 5-methyl-3-hydroxyisoxazole (1) with 3-substituted cyclopropanecarboxylic chlorides (3) in the presence of triethylamine (TEA) in acetonitrile yields predominantly O-acylated products (4).The N-acyl isomers (5) are afforded regiospecifically using trimethylsilyl ether of 3-hydroxyisoxazole (2).

Ultrasonically Assisted Regioselective Nitration of Aromatic Compounds in Presence of Certain Group V and VI Metal Salts

Ultrasonically assisted nitration reactions (USANR) with anilides, moderately activated and non-activated aromatic compounds underwent smoothly and afforded good yields of products with high regio selectivity. Observed longer reaction times (6 - 8 hrs.) in metal catalyzed reactions reduced to (1 - 2 hrs.) under sonication. When ortho position is blocked para derivatives are obtained, and ortho nitro products are obtained when para position is blocked. In case of USANR of aromatic carbonyl and related compounds the effect of sonication is much more effective. The reactions could be completed only in few minutes.

A Facile and Efficient One-Pot Regioselective Synthesis of 2-Hydroxyalkyl Dithiocarbamates under Catalyst-Free Conditions

A simple catalyst-free, and highly regioselective approach to 2-hydroxyalkyl dithiocarbamates is described which involves a one-pot reaction of various amines and carbon disulfide,CS2, with epoxides in ethanol at room temperature.