Chlorination and oxidation of 4-fluoro-5-tetrafluoroethyl-1,2-dithiole-3-thione

Chlorination of 4-fluoro-5-(1,1,2,2-tetrafluoroethyl)-1,2-dithiole-3-thione with an equimolar amount of chlorine or sulfuryl chloride gives 3-chlorosulfanyl-4-fluoro-5-(1,1,2,2-tetrafluoroethyl)-1,2-dithiolium chloride. The reaction of the title compound with excess chlorinating agent leads to 3,3,4,5-tetrachloro-4-fluoro-5-(1,1,2,2-tetrafluoroethyl)-1,2-dithiolane. By oxidation and oxidative imination of 4-fluoro-5-(1,1,2,2-tetrafluoroethyl)-1,2-dithiole-3-thione, the corresponding S-oxide and sulfimide were obtained, respectively.     

Diarylnonanoids and their glucosides from Erica cinerea

The reinvestigation of Erica cinerea fresh aerial parts led to the isolation of two new diarylnonanoid aglycones along with their glucosides. From spectroscopic data, their structures were elucidated as rel-(3R,7R)-1,9-bis(p-hydroxyphenyl)-3,7-dihydroxynonan-5-one named ericanone, ericanone 3-β-d-glucoside, (3S)-3,7-anhydro-6,7-dehydroericanone and (3S)-3,7-anhydro-6,7-dehydroericanone 4′-β-d-glucoside. Contrary to the numerous diarylheptanoids more frequently distributed in the plant kingdom, the rare diarylnonanoids were previously restricted to the genus Myristica of the Myristicaceae plant family.     

Reaction of adenine with an α-chlorooxetane: An approach to the synthesis of oxetane nucleosides

The reaction of adenine with 3,5-anhydro-5R-chloro-1,2-O- isopropylidenexylofuranose, a stable α-chlorooxetane, gives a mixture of the two epimers of 5-[9-adenyl]-3,5-anhydro- 1,2-O-isopropylidenexylofuranose; the structure of 5R-[9- adenyl)-3,5-anhydro-1,2-O-isopropylidenexylofuranose was established by X-ray crystallography.     

Organoborierung von alkinylstannanen: XV. Synthese von 1,2-dihydro-1,2,5-disilaborepinen

The reaction between 1,2-diethynyl-tetramethyldisilane (1) and two equivalents of diethylaminotrimethylstannane (2) leads to 1,2-bis(trimethylstannylethynyl)-tetramethyldisilane (3). The new alkyne derivative 3 reacts, already at room temperature, with trialkylboranes, R₃B (5) (R = Me, Et), quantitatively to give 1,1,2,2-tetramethyl-3,7-bis(trimethylstannyl)-4,5,6-trialkyl-1,2-dihydro-1,2,5-disilaborepines (6). The reaction is much slower with R = Prⁱ which allows detection of intermediates by NMR spectroscopy. All products are characterized by ¹H, ¹¹B, ¹³C, ²⁹Si and ¹¹⁹Sn NMR data.     

Isobaric vapour–liquid equilibria for mixtures containing halogenated hydrocarbons at atmospheric pressure: I. Binary mixtures of trichloromethane+1,2-dichloroethane, 1,2-dichloroethane+1,1,2,2-tetrachloroethane,trichloromethane+1,1,2,2-tetrachloroethane and n-heptane+1,1,2,2-tetrachloroethane

Vapour–liquid equilibria at atmospheric pressure for mixtures of trichloromethane+1,2-dichloroethane, 1,2-dichloroethane+1,1,2,2-tetrachloroethane, trichloromethane+1,1,2,2-tetrachloroethane and n-heptane+1,1,2,2-tetrachloroethane have been determined. These have been shown to be thermodynamically consistent.     

Chemistry of organosilicon compounds 118. Novel ring contraction reaction of (η4-1,2-disilacyclohexadiene)iron tricarbonyls

1,1,2,2-Dimethyl-3,6-diphenyl-1,2-disilacyclohexadiene reacts with iron pentacarbonyl or diiron nonacarbonyl to give the corresponding (diene)iron tricarbonyl complex which undergoes novel ring contraction reaction to (η⁴-1,1-dimethyl-2,5-diphenyl-1-silacyclopentadiene)iron tricarbonyl on thermolysis at 160°C. Similar results were observed with 1,1,2,2-tetramethyl-3,4,5,6-tetraphenyl-1,2-disilacyclohexadiene.     

Excess volumes of chlorobenzene and bromobenzene with some chloroethanes at 303.15 and 313.15 K

Volume changes on mixing for the binary systems formed by chlorobenzene with 1,2-dichloroethane, 1,1,1-trichloroethane and 1,1,2,2-tetrachloroethane, and by bromobenzene with 1,2-dichloroethane, 1,1,1-trichloroethane and 1,1,2,2-tetrachloroethane, have been measured as functions of composition at 303.15 and 313.15 K. The measured excess volumes are positive over the entire range of composition for the binary systems chlorobenzene + 1,2-dichloroethane and bromobenzene + 1,2-dichloroethane at 303.15 K, and for chlorobenzene + 1,1,2,2-tetrachloroethane at 313.15 K. The measured volumes V^E are negative over the entire composition range for the remaining systems, except for the system chlorobenzene + 1,1,2,2-tetrachloroethane at 303.15 K, where an inversion of the sign of V^E is observed over part of the concentration range.     

Two ethyl 2-deoxy-α-d-hexo-3,7-pyranoso-3-octulosonate derivatives

In each of the two pyran­oid sugars, ethyl 2-deoxy-4,5,6,8-tetra-O-acetyl-α-d -gluco-3,7-pyran­oso-3-octulosonate, C₁₈H₂₆O₁₂, and ethyl 2-deoxy-4,5,6,8-tetra-O-benzyl-α-d -galacto-3,7-pyranoso-3-octulosonate, C₃₈H₄₂O₈, the anomeric configuration is α. The acetoxy­methyl substituent on the hexo­pyran­ose ring of the former compound and the ethoxy­carbonyl­methyl substituents in both sugars all have the gauche–trans conformation, while the benzyl­oxy­methyl substituent of the galacto­pyran­ose sugar has the trans–gauche conformation. In each structure, the anomeric hydroxy group forms an intramolecular hydrogen bond with the carbonyl O atom of the ethoxy­carbonyl­methyl substituent.     

Formation of 1,2-dioxolane in the singlet oxygenation of cyclopropane

Reaction of 1,1,2,2-tetraanisylcyclopropane (1a) with both thermally and photochemically generated singlet oxygen afforded the corresponding 1,2-dioxolane 2a quantitatively. Singlet oxygenation of two stereoisomeric 1,2-dianisyl-1,2-ditolylcyclopropanes (1b and 1c) gave a mixture of 1,2-dioxolanes 2b and 2c via a non-stereospecific addition in both cases.     

Some reactions of polyfluoroalkyl ethers and the preparation of bis(trifluorovinyl) ether

d1 and meso Bis (1,2,2-trifluoroethyl) ether and 1,1,2,2 tetrafluoroethyl 1,1,2-trifluoroethyl ether with aluminium halides or boron trichloride yield halogenopolyfluoroalkyl ethers. The epimerisation of the d1 and meso stereoisomers is discussed. Chlorination of bis (1,2,2-trifluoroethyl) ether and 1,1,2,2-tetrafluoroethyl 1,2,2-trifluoroethyl ether gives new chloropolyfluorodiethyl ethers and from bis (1,2-dichlorotrifluoroethyl) ether, bis (trifluorovinyl) ether is obtained by dechlorination.     

Intramolecular 1,5- versus 1,6-hydrogen abstraction reaction promoted by alkoxy radicals in carbohydrate models

[reaction: see text] The alkoxy radical generated by reaction of 3,7-anhydro-2-deoxyoctitols with (diacetoxyiodo)benzene (DIB) and iodine abstracts regioselectively either the proton at C7 or that at C4 depending on the electronegativity of the substituent at C4. The correct election of this substituent can switch the reaction to give 2,9-dioxabicyclo[3.3.1]nonane or hexahydro-2H-furo[3,2-b]pyran ring systems.     

1,1,2,2-四甲基-1,2-二氯二硅烷裂解机理的研究

利用量子化学知识对典型的二硅烷高沸物1,1,2,2-四甲基-1,2-二氯二硅烷的裂解机理进行理论研究。结果表明,在无催化剂和常温常压下,1,1,2,2-四甲基-1,2-二氯二硅烷以CHCl3作为裂解气的反应分为两步进行,均为放热反应,其速控步第一步的正反应活化能为352.949kJ/mol。     

利用激光诱导荧光技术研究Ca(1S0)与氯代乙烷的反应

The internal state distributions of nascent CaCl formed in the reactions Ca + (1,1) and (1,2) C_2H_4Cl_2、(1,1,2) C_2H_2Cl_3, (1,1,2,2) C_2H_2Cl_4 have been studied by means of the laser induced fluorescence (LIF) in the beam-gas apparatus. The results showed that the vibrational distributions of the CaCl products from Ca+ (1, 1) C_2H_4Cl_2. (1,1,2,2) C_2H_2Cl_4 are similar to vibrational distributions of the CaCl products from Ca + CH_2Cl_2、CHCl_3, respectively. However, the vibrational distribution of the CaCl product from Ca+(1,1,2) C_2H_3Cl_3 is equivalent to the combination of that from Ca+(1,2) C_2H_4Cl_2 and Ca+(1,1,2,2) C_2H_2Cl_4. No LIF signal has been found in the reaction Ca+(1,1) C_2H_4Cl_2.     

Stereoselective Glycosidic Coupling Reactions of Fully Benzylated 1,2-Anhydro Sugars with N-Tosyl- or N-Benzyloxycarbonyl-l-serine Methyl Ester

Abstract

The glycosidic coupling reaction of 1,2-anhydro-3,4,6-tri-O-benzyl-β-d-mannopyranose (7), 1,2-anhydro-3,4,6-tri-O-benzyl-α-d-galactopyranose (21), and 1,2-anhydro-3,4-di-O-benzyl-α-d-xylopyranose (18) with N-tosyl- (10) or N-benzyloxycarbonyl- (11) L-serine methyl ester provides a new stereocontrolled synthesis of 1,2-trans linked glycopeptides. The 1,2-anhydro sugars are shown to react smoothyl with 10 or 11 in the presence of Lewis acid (ZnCl₂ or AgOTf) as well as powdered 4A molecular sieves in CH₂Cl₂ at room temperature to afford glycosyl serine derivatives with high stereoselectivity and high yield in less than 30 min. An improved method using 2-O-acetyl-3,4,6-tri-O-benzyl-α-d-mannopyranosyl chloride (6) as the key intermediate for ring closure was applied for the synthesis of 1,2-anhydro-3,4,6-tri-O-benzyl-β-d-mannopyranose.     

Reaction of an alkyne with dinickel-diphenylsilyl complexes. An emissive disilane formed via the consecutive Si-C and Si-Si bond-making processes

[{Ni(dmpe)}(2)(μ-SiHPh(2))(2)] (dmpe = 1,2-bis(dimethylphosphino)ethane) reacted with PhC≡CPh to yield fluorescent 1,2-bis{(E)-1,2-diphenylethenyl}-1,1,2,2-tetraphenyldisilane via addition of the Si-H bond of the ligand to the alkyne and subsequent coupling of the tertiary silyl ligands forming the Si-Si bond.     

New Models for the Study of the Racemization Mechanism of Carbodiimides. Synthesis and Structure (X-ray Crystallography and (1)H NMR) of Cyclic Carbodiimides

The crystal and molecular structure of carbodiimides 2 (5,6,18,19-tetradehydro-5,12,13,18,25,26-hexahydrotetrabenzo[d,h,m,q][1,3,10,12]tetraazacyclooctadecine) and 3 (8,10,22,24-tetraazapentacyclo[23.3.1.1(3,7).1(11,15).1(17,21)]dotriaconta-1(29),3,5,7(32),8,9,11,13,15(31),17,19,21(30),22,23,25,27-hexadecaene) have been determined. The activation barriers for the racemization of carbodiimides 1 (6,7-dihydrodibenzo[d,h][1,3]diazonine), 2, and 3 have been determined. While 1 presents a relatively high barrier (17.4 kcal mol(-)(1)), 2 and 3 have very low activation barriers (between 5 and 7 kcal mol(-)(1)). We tentatively conclude that open-chain and large-ring carbodiimides racemize by nitrogen inversion or trans-rotation while medium-size cyclic carbodiimides racemize by cis-rotation.     

Intramolecular charge resonance in dimer radical anions of di-, tri-, tetra-, and pentaphenylalkanes

Intramolecular dimer radical anions of di-, tri-, tetra-, and pentaphenylalkanes were investigated on the basis of absorption spectral measurements during γ-radiolysis in 2-methyltetrahydrofuran (MTHF) glassy matrix at 77 K and theoretical calculations. The absorption spectrum of 1,1,2,2-tetraphenylethane (1,1,2,2-Ph(4)E) radical anion showed two bands in the near-infrared (NIR) region (900-2600 nm). One band observed at shorter wavelength than 2000 nm is assigned to the intramolecular charge resonance (CR) band between two phenyl groups of the 1,1-diphenylmethyl chromophore (1,1-dimer radical anion). The intramolecular CR band of the 1,1-dimer radical anion was observed for various alkanes having 1,1-diphenylmethyl chromophore such as 1,1,1-triphenylmethane (1,1,1-Ph(3)M), 1,1,1,1-tetraphenylmethane (1,1,1,1-Ph(4)M), and so on. The other intramolecular CR band observed at longer wavelength than 2200 nm is assigned to intramolecular dimer radical anion between two phenyl groups of the 1,2-diphenylethyl chromophore (1,2-dimer radical anion). The intramolecular CR band of the 1,2-dimer radical anion was observed for various alkanes having a 1,2-diphenylethyl chromophore, such as 1,1,2-triphenylethane (1,1,2-Ph(3)E), 1,1,2,2-Ph(4)E, and 1,1,1,2,2-pentaphenylethane (1,1,1,2,2-Ph(5)E) and so on. No dimer radical anion was observed for 1,n-diphenylalkanes (n > 2) without 1,1-diphenylmethyl chromophore. The relationship between the structure and negative charge delocalization over two phenyl groups connected by an sp(3) carbon is discussed.     

Synthesis of new polydentate pyrazolyl‐ethene ligands by interaction of 1H‐pyrazole and 1,1,2,2‐tetrabromoethane in a superbasic medium

Reaction of pyrazole and 1,1,2,2‐tetrabromoethane in a superbasic medium dimethylsulfoxide‐potassium hydroxide was investigated, and a number of pyrazolyl‐ and bromo‐substituted ethenes, which are the products of concurrent substitution and elimination reactions, were identified. Carrying out the reaction using different reagent mole ratios allowed to selectively isolate Z‐1,2‐bis(pyrazol‐1‐yl)ethene, 1,1,2‐tris(pyrazol‐1‐yl)ethane, and 1,1,2,2‐tetrakis(pyrazol‐1‐yl)ethane. Crystal structure of {Z‐1,2‐bis (pyrazol‐1‐yl)ethene}dichlorozinc was established using X‐ray diffraction method. J. Heterocyclic Chem., (2011).     

The first successful ring opening polymerization at the Si---Si bond: a novel o-(disilanylene)phenylene polymer

A new type of polymer, poly[o-(disilanylene)phenylene] was prepared via ring opening polymerization, at the Si---Si bond, of 1,1,2,2-tetramethyl-1,2-disilabenzocyclobutene.     

Synthesis and x-ray crystal structure of a stable α-chlorooxetane

The Barton modification of the Hunsdiecker reaction is the key step in the preparation of 3,5-anhydro-5R-chloro-1,2-O-isopropylidenexylofuranose (1), a stable α-chlorooxetane.