CAN TRICHLOROMETHANE SULFONYL BROMIDE BE USED AS AN ADDENDUM AS WELL AS A TELOGEN IN ITS ADDITION REACTION T0 VINYLIDENE FLUORIDE?

CCl_3SO_2Br used as a "telogen" reacts with CH_2=CF_2 to give mainly the "mono-adduct" CCl_3CH_2CF_2Br, together with very small amouats of CCl_3CF_2CH_2Br, CCl_2BrCH_2CF_2Br andthe "di-adduct" CCl_3(CH_2CF_2)_2Br. The result indicates that CCl_3SO_2Br can be used as anaddendum in trichloromethyl-bromo-addition reactions to olefins.     

PERFLUORO-AND POLYFLUORO-SULFONIC ACIDS (ⅩⅤ)——GENERATION OF DIFLUOROCARBENE AND FLUOROSULFONYLDIFLUOROMETHIDE ION FROM METHYL α-FLUOROSULFONYLDIFLUOROACETATE

The decarbomethoxylation reactions of MeOCOCF_2SO_2F (1) can be induced readily by a varietyof nucleophiles. For example, X~- (Cr~-, Br~-, I~-), CNS~-, Et_3N, C_5H_5N make facile attack onmethyl carbon of 1 with subsequent elimination of CO_2, SO_2 and F~- resulting in generation of CF_2:. Innonaqueous organic solvents fragmentation of 1 was extremely fast and apparently might take place withsimultaneous elimination of SO_2 and F~- and formation of CF_2:. In aqueous organic solvents the inter-mediate FSO_2CF_2~- may be trapped by protonation into HCF_2SO_2F (2) as well as predominantly furthereliminate SO_2 and F~- yielding CF_2:. Alkoxide ions could not decompose 1 to produce CF_s:, but wereable to attack the sulfur atoms to afford the corresponding sulfonates, MeOCOCF_2SO_2Z (10) (Z=OCH_2-CF_2CF_2H, OC_6H_5). In the absence of solvent Et_2NH mainly induced the decomposition of 1 to form CF_2:with some attack on carboxyl carbon to give the corresponding amide FO_2SCF_2CONE_(t2).     

Synthesis of 5-Fluoroalkyl Isoxazolidines via 1,3-Dipolar Cycloaddition of Ethyl 2-Hydropolyfluoroalk-2-enoates with Nitrones

1,3-Dipolar cycloaddition reactions of ethyl 2-hydropolyfluoroalk-2-enoates (1) with some nitrones were described. The reaction of 3,4-dihydroisoquinoline N-oxide (2) with 1 took place readily in methylene chloride at room temperature to give the corresponding 5-fluoroalkylisoxazolidines regioselectively as a mixture of two diastereoisomers (trans and cis) in high yields, while longer reaction time and higher temperature were needed in the case of non-cyclic nitrones. Under similar conditions the reaction of quinoline N-oxide (14) with 1 did not give the expected adducts and a ring-opening product was obtained.     

焦脱镁叶绿酸甲酯的Vilsmeier反应合成δ-meso-甲酰乙烯基卟吩和苯并异细菌卟吩

From methyl pyropheophorbide-a (MPPa, 1), the vinyl group of methyl pyropheophorbide-a was converted into alkylcarbonyl group by Grignard reaction and oxidization to give chlorins 2, 3 and 5. The Vilsmeier reaction of nickel 3-substituent-3-devinylpyropheophorbide-a (6), which was prepared by the metallation with nickel acetate, with 3-dimethylamino-acrolein/phosphoryl chloride (3-DMA/POCl3) was carried out to give δ-meso-formylvinylpyropheophorbide-a (7) in good yield. The benzoisobacterichlorin (8) was obtained by the treatment of 7b with concentrated sulfuric acid.     

Photochemical reaction of magnesium tetraphenyl porphyrin with sulfur dioxide

<正>The photochemical reaction of magnesium tetraphenyl porphyrin(MgTPP) with sulfur dioxide(SO_2) was investigated in dichloromethane(CH_2Cl_2) by steady-state fluorescence,UV-vis absorption,MS,and XRD spectroscopic techniques.These spectra showed that under irradiation MgTPP reacted with SO_2 to form 1:1 molecular adduct at first step.During the process of keeping irradiation and maintaining the flow of SO_2,SO_2 was reduced into S~(2-) by MgTPP and the results were detected using MS and XRD techniques.Understanding the photochemical reaction of MgTPP with SO_2 is of key interest in elucidating fundamental photochemical reaction mechanisms associated with this class of chlorophyll in the presence of SO_2.     

Double [3 + 2] cycloaddition of nitrile oxides with allenoates: Synthesis of spirobidihydroisoxazoles

The double [3+2] cycloaddition of allenoates with nitrile oxides was presented. The reaction worked well under mild reaction conditions to give the spirobidihydroisoxazole in moderate to excellent yields with excellent diastereoselectivities.     

Density Functional Study on the Reaction Mechanism for the Reaction of Ni^＋ with Ethane

The mechanism of the reaction of Ni^ (^2D) with ethane in the gas-phase was studied by using density functional theory.Both the B3LYP and BLYP functionals with standard all-electron basis sets are used to give the detailed information of the potential energy surface (PES) of [Ni,C2,H6]^ . The mechanisms forming the products CH4 and H2 in the reaction of Ni^ with ethane are proposed.The reductive eliminations of CH4 and H2 are typical addition-elimination reactions.Each of the two reactions consists of two elementary steps:C-C or C-H bond activations to form inserted species followed by isomerizations to from product-like intermediate.The rate determining steps for the elimination reactions of forming CH4 and H2 are the isomerization of the inserted species rather than C-C or C-H bond activations .The elimination reaction of forming H2 was found to be thermodynamically favored compared to that of CH4.     

Catalytic Systems Containing p-Toluenesulfonic Acid for the Coupling Reaction of Formaldehyde and Methyl Formate

The coupling reaction of formaldehyde(FA)and methyl formate(MF)to form methyl glycolate(MG)and methyl methoxy acetate(MMAc),catalyzed by p-toluenesulfonic acid(p-TsOH)as well as assisted by different kinds of solvents or Ni-containing compounds,had been investigated.The results showed that when the reaction was carried out at 140℃,with a molar ratio of FA to MF of 0.65:1, molar fraction of p-TsOH to total feedstock of 11.0%,and reaction time of 3 h,the yield of MG and MMAc was 31.1% and 17.1%,respectively,p-TsOH catalyzed the coupling reaction by means of the synergistic catalysis of protonic acidity and soft basicity.Adding extra solvents to the reaction system was unfavorable for the reaction.The composite catalytic system consisting of p-TsOH and NiX_2(X=Cl,Br,I)exhibited a high catalytic performance for the coupling reaction,and NiX_2 acted as a promoter in the reaction,whose promotion for the catalysis increased in the following order:NiCl_2相似文献   

Efficient dehydration of carbohydrates to 5-hydroxymethylfurfural in ionic liquids catalyzed by tin(Ⅳ) phosphonate and zirconium phosphonate

In this work,we synthesized tin(IV)phosphonate(SnBPMA)and zirconium phosphonate(ZrBPMA)by the reaction of SnCl4·5H2O or ZrOCl2·8H2O with N,N-bis(phosphonomethyl)aminoacetic acid,which was synthesized from a biomaterial glycine through a Mannich-type reaction.The SnBPMA and ZrBPMA were very efficient heterogeneous catalysts for the dehydration of fructose to produce 5-hydroxymethylfurfural(HMF),and the SnBPMA had higher activity than the ZrBPMA.The effects of solvents,temperature,reaction time,and reactant/solvent weight ratio on the reaction catalyzed by SnBPMA were investigated.It was demonstrated that the yield of HMF could reach 86.5%with 1-ethyl-3-methylimidazolium bromide([Emim]Br)as solvent,and the SnBPMA and SnBPMA/[Emim]Br catalytic system could be reused five times without considerable reduction in catalytic efficiency.Further study indicated that the SnBPMA and ZrBPMA in[Emim]Br were also effective for the dehydration of sucrose and inulin to produce HMF with satisfactory yields.     

Study on Lewis acid promoted condensation of allylalkoxysilanes with (-)-menthyl glyoxylate

Allylalkoxydimethylsilanes (2) condense with (-)-menthyl glyoxylate (3) in the presence of Lewis acid to give optically active menthyl 2-hydroxy-4-pentenoate (7) with optical purity of 31-42%. Factors affecting the yield and de of 7 have been examined. The stereochemistry of transition state of the reaction was discussed.     

Synthesis and reactivity of 3-(trichlorogermyl)propanoic acid and 3-(triphenylgermyl) propanoic acid

3-(Trichlorogermyl)propanoic acid (la) reacts with phenylmagnesium bromide in malar ratio 1:4 to give 3-(triphenylgermyl)propanoic acid (2a).In the compounds la and 2a theβ-carboxylic functional group shows some unusual properties when they react with excess of phenylmagnesium bromide.The compound la reacts with phenylmagnesium bromide in molar ratio 1:5 to give phenyl 2-(triphenylgermyl)ethylketone (3a) and in molar ratio 1:6 to give l,l-diphenyl-3-(triphenylgermyl)propanol (4a).The compound 2a reacts with phenylmagnesium bromide in molar ratio 1:2 to give 3a and in molar ratio 1:3 to give 4a also.Dehydration of the compound 4a with dilute hydrochloric acid seems especially easy.Moreover,the compound la reacted with phenylmagnsium bromide in molar ratio 1:6,then the mixture was treated with dilute hydrochloric acid to give 1,1-diphenyl-3-(triphenylgermyl)-1-propene (5a) in one pot reaction.Alkyl Ge-C bond in the compound 5a can be cleaved selectively by lithium aluminium hydride ( LiAlH4) in good yiel     

An Improved Protocol for Regioselective Ring-Opening of Sulfonyl Aziridines with Iodine Promoted by PPh3

A new route to synthesize β-iodo amines from sulfonyl aziridines and iodine was developed in the presence of PPh3. This ring-opening reaction was an efficient and simple process to give fl-iodo amines in excellent yields with high chemoselectivity.     

Synthesis of 1-Bromo-3-methoxy-4-propoxy-5-iodobenzene——A Novel Efficient Process for the Synthesis of Brominated Aromatic Compound

The reaction of aromatic carboxylic acid with oxalyl chloride gives rise to the corresponding acid chloride which without purification is treated with the sodium salt of mercaptopyridine oxide in the presence of 2,2-azo-bisisobutyronitrile (AIBN), radical initiator to give a brominated aromatic compound. After etherification and oxidation, 5-iodovaniline was converted to trisubstituted benzene carboxylic acid which give 1-bromo-3-methoxy-4-propoxy-5-iodobenzene by this new brominating process with a yield of 74%.     

Study on the alkylation reaction of guanine and N-acetylguanine and the synthesis of 1''''-C alkylated carba-DHPG analogues

The alkylation reaction of guanine and N-acetylguanine with model compounds such as isopropyl bromide or 4-heptyl tosylate were studied. The reaction conditions such as temperature, solvent, base, and catalyst were examined for their effects on the reaction rate, and the yield and regioselectivity of the coupling reaction. The highest yield was obtained by using DMSO as the solvent. The reaction proceeded in a homogenous manner to give higher yield of 9-N and 7-N substituted product in a mole ratio of 1:1. The ratio could be raised to 2:1 if dibenzo-18-crown-6 was used as a catalyst. Using the above procedure, three carba-DHPG analogues bearing different 1'-C alkyl side chains were synthesized.     

On the Reaction Mechanism of Br2 with OCS

The reaction mechanism of photochemical reaction between Br2 (^1∑) and OCS (^1∑) is predicted by means of theoretical methods. The calculated results indicate that the direct addition of Br2 to the CS bond of OCS molecule is more favorable in energy than the direct addition of Br2 to the CO bond. Furthermore, the intermediate isomer syn-BrC(O)SBr is more stablethe rmodynamically and kinetically than anti-BrC(O)SBr. The original resultant anti-BrC(O)SBr formed in the most favorable reaction channel can easily isomerize into the final product syn-BrC(O)SBr with only 31.72 kJ/mol reaction barrier height. The suggested mechanism is in good agreement with previous experimental study.     

Polystyrene-supported Phenol/DMAP： an Efficient Binary Catalyst System for CO2 Fixation to Give Cyclic Carbonates

Polystyrene-supported phenol （PS-PhOH） was successfully synthesized by alkylation reaction of phenol with 2% DVB cross-linked chloromethylated polystyrene and characterized by IR spectra and elemental analysis. In conjunction with an organic base such as DMAP, DBU, triethylamine （Et3N）, diethylamine （Et2NH） or pyridine, the PS-PhOH could effectively catalyze the coupling reaction of carbon dioxide with epoxides to give cyclic carbonates in high yield and selectivity under mild conditions. The binary catalyst system of the PS-PhOH/DMAP was found to be the most active. The influence of reaction temperature, carbon dioxide pressure and reaction time on the yield of product was carefully investigated. The PS-PhOH could be recycled by simple filtration for at least up to ten times without loss of catalytic activity.     

The Synthesis, Reaction and Crystal Structures of Ethyltetramethylcyclopentadienylruthenium Compounds

Pentamethylcyclopentadienyl-trimethylphosphine-metal compounds play an important role in the activation studies of saturated hydrocarbons. A method to synthesize ethyltetramethylruthenium compounds was established, which started from the reaction of RuCl_3. H_2O with ethyltetramethylcyclopentadiene to give a dimer compound of 2. When 2 was reacted with different amounts of trimethylphosphine, compounds 3 [C_5Me_4EtRu(PMe_3)Cl_2] and 4 [(C_5Me_4Et)Ru(PMe_3)_2Cl] were obtained. Compound 3 is a 17-electron species which is in formula similar to Bergman's Ir compound used in hydrocarbon activation reaction, but might be more reactive because of its unsaturated electron structure. The crystal structure analysis of compounds 2, 3 and 4, showed that the ruthenium atom was coordinated in a "threeleg-piano-stool" geometry in all the three compounds. The Ru—Cl bond in 3 and 4 was lengthened, making it labile to other substitution reactions.     

Direct synthesis of per(poly)fluoroalkylmethyl-substituted electrophilic cyclopropane derivatives

A convenient and direct per(poly)fluoroalkylmethyl-mtroducing cyclopropanation reaction was described. In the presence of CrCl3/Fe, per(poly)fluoroalkyl iodides reacted with diethyl allylmalonate and its analogs to give per(poly)fluoroalkylmethyl-substituted electrophilic cyclopropane derivatives in high yields. This reaction was considered to proceed by two steps: radical addition followed by cyclopropanation.     

1,3-Dipolar Addition of Methyl α-Diazoacetoacetate to Enamines： A New Synthetic Route to 5-Amino-4,5-dihydrofurans

The reaction of methyl α-diazoacetoacetate with enamines catalyzed by dirhodium and copper complexes underwent formal 1,3-dipolar addition to give 5-amino-4,5-dihydrofurans in moderate yields. The reaction was suggested to proceed via a nucleophilic addition of enamines to rnetal-carbenes and a subsequent intramolecular cyclization of the resulting zwitterionic intermediates.     

Gal3 Catalyzed Tetrahydropyranylation of Alcohols and Phenols

In dichloromethane, the nucleophilic addition of alcohols or phenols to 3,4-dihydro-2H-pyran (DHP) was catalyzed effectively by gallium triiodide which was generated in situ by the reaction of gallium metal and iodine to give the corresponding tetrahydropyranyl acetals in good to excellent yields.