Bismuth(III) Chloride; A Mild and Efficient Catalyst for Synthesis of Thiiranes from Oxiranes

A simple and efficient method for the conversion of oxiranes to the corresponding thiiranes using ammonium thiocyanate (NH₄SCN) and catalytic amounts of bismuth(III) chloride (BiCl₃) is described. The yields obtained are excellent.     

Chiral Thietanes and Thiethane-1, 1-dioxides—Novel Building Blocks for Liquid Crystals -

The synthesis of chiral thietanes and chiral thiiranes from oxiranes under Mitsunobu conditions is described. One chiral thietane was oxidized to the corresponding thietane-1, 1-dioxide. ¹H-NMR, ¹³C-NMR, IR, MS data of the new compounds are given. In connection with a mesogenic group liquid crystal behavior could be observed for the thietane and the thiirane as well.     

Conversion of Oxiranes to Thiiranes Catalyzed with Silica Gel–Supported Aluminium Chloride

Silica gel–supported aluminium chloride, SiO₂‐AlCl₃, catalysizes the efficient conversion of different oxiranes to their corresponding thiiranes in the presence of thiourea under nonaqueous conditions.     

SOLVENT-FREE CONVERSION OF OXIRANES TO THIIRANES WITH THIOUREA

A simple and efficient method for the conversion of various oxiranes to the corresponding thiiranes using thiourea under solvent free conditions is described.     

Palladium-catalyzed alkylation of vinyl oxiranes with substituted allenes. Direct access to bifunctionalized allylic alcohols

The first palladium-catalyzed alkylation of vinyl oxiranes with substituted allenes to form functionalized allylic alcohols is described. The reaction of activated allenes 5 with vinyl oxiranes 1 in the presence of catalytic amounts of Pd(PPh(3))(4) (10 mol %) and 1,3-bis(diphenylphosphino)propane (dppp) (20 mol %) in THF at 60 degrees C gave the corresponding allylic alcohols 6 in good to excellent yields. The allylic alcohols were obtained in different ratios of trans/ cis isomers.     

Rearrangement thermique de cycles a 3 chainons α-ethyleniques α'-acetyleniques trans

The thermal rearrangement of α-ethylenic α'-acetylenic oxiranes and aziridines is described. Trans-vinyl-ethynyloxirane 1a yields trans (3aT) and cis (3aC) formyl-ethynyl-cyclopropane and dihydrofuran4a. The cis isomer 1aC yields the same products, but by a different mechanism. The proposed mechanism is supported by the analogous conversion of oxiranes substituted on the acetylenic carbon (1e and 1d). Thermolysis of trans N-tert-butyl-2-ethynyl-3-vinylaziridine leads to N-tert-butyl-1H-azepine.     

Synthesis and Structure of Some Aryl-substituted Thiiranes

A number of aryl-substituted 1,2-chlorohydrins was prepared by treating 1,2-epoxy-3-chlororopane with arylmagnesium bromide. The reaction of the aryl-substituted 1,2-chlorohydrins with sodium hydroxide solution furnished the corresponding oxiranes, the key compounds in the synthesis of a number of previously unknown thiiranes.     

Some addition reactions of pentafluorothiophenol and pentafluorobenzenesulfenyl chloride

The addition reactions of pentafluorothiophenol, C₆F₅SH, and pentafluorobenzenesulfenyl choloride, C₆F₅SCl, with various unsaturated systems, including alkenes, alkynes, oxiranes, thiiranes, diazo compounds, aldehydes, ketones, and nitriles have been examined. The physical properties of the new compounds are reported together with some spectroscopic data.     

Ferroelectric liquid crystals derived from (S)‐2‐(6‐methoxy‐2‐naphthyl)propionic acid with non‐fluorinated or semi‐fluorinated alkanes at a chiral terminal chain

Two series of ferroelectric liquid crystals derived from (S)‐2‐(6‐methoxy‐2‐naphthyl)propionic acid, with non‐fluorinated or semi‐perfluorinated alkanes positioned at a chiral terminal chain, have been synthesized and characterized by differential scanning calorimetry, polarizing optical microscopy and electro‐optical measurements. The non‐fluorinated compounds, 1‐hexyl (S)‐2‐{6‐[4‐(4‐alkanoyloxyphenyl)benzoyloxy]‐2‐napthyl}propionates exhibit rich mesomorphism—the BP_II, N*, TGB_A*, SmA* and SmC* phases. The fluorinated compounds display only the SmA* and SmC* phases, suggesting that the fluorination promotes the formation of smectic phases. In addition, the SmA* and SmC* phases of the fluorinated compounds have enhanced thermal stability as compared with the corresponding phases of the non‐fluorinated compounds. The spontaneous polarization (P _s values) for the non‐fluorinated compounds are higher than those of the fluorinated compounds at any reduced temperature below the SmA*–SmC* transition. The electro‐optical responses measured for these compounds in the ferroelectric phase displayed thresholdless, V‐shaped switching.     

Thia-6 diphényl-3,3 sila-3 (et germa-3)bicyclo[3.1.0]hexanes

6-Thia-3,3-diphenyl-3-sila-(and 3-germa-)bicyclo[3.1.0]hexanes are prepared from the corresponding metallaoxiranes using triphenylphosphorus sulfide with trifluoroacetic acid as solvent. These thiiranes are unstable compared to the corresponding oxiranes. Partial desulfurization results from thermic or chemical processes leading to 1-metallacyclopent-3-enes. Cyclometallathianes are potential precursors of metallathiones and thiofunctional metallacyclopentanes.     

非对称环硫乙烷的区域选择性亲核开环反应

环硫乙烷与它的氧类似物环氧乙烷和氮类似物氮杂环丙烷一样,是一类重要的有机合成中间体,在医药和农用化学品工业领域也得到广泛应用。通过开环和异构化反应,还广泛用于制备硫醇和硫醚等含硫化合物。本文总结了常用亲核试剂对非对称环硫乙烷的亲核开环反应及其区域选择性。环硫乙烷的亲核开环反应通常只受空间效应影响,亲核试剂进攻非对称环硫乙烷位阻小的碳原子,对于烯基取代的环硫乙烷有时可以进攻烯基的β碳原子发生SN2’开环反应。强亲核性的亲核试剂容易致使环硫乙烷脱硫生成烯烃,而亲核性相对较弱的亲核试剂容易发生多聚反应生成多硫醚。在Lewis酸存在下,电子效应会对开环反应的区域选择性产生影响,甚至起主导作用。虽然烷基取代环硫乙烷在Lewis酸存在下的开环仍然主要发生在其取代基少的碳原子上(位阻控制),但受电子效应影响,芳基和烯基取代环硫乙烷的亲核开环,其亲核试剂一般倾向于进攻环硫乙烷的芳甲位和烯丙位碳原子(电子效应控制)。     

Synthesis and properties of benzyl-substituted thiiranes

The reaction of phenyl- and p-tolylmagnesium bromides, as well as di, tri, and tetramethylbenzene, with epichlorohydrin was used to synthesize the corresponding chlorohydrins, which were then converted to various benzyl-substituted oxiranes and thiiranes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 598–602, May, 1988.     

含绿色荧光蛋白发色团双自由基分子的非线性光学性质

采用密度泛函理论(DFT)方法研究了系列含绿色荧光蛋白发色团双自由基分子光学异构体的几何结构、极化率(αs)和第一超极化率(βtot).结果表明,引入电子给受体取代基使分子的极化率增大,而对第一超极化率有不同影响.对于光照前的反式结构,引入电子受体βtot值增加,且βtot值随取代基吸电子能力的增强而增大;引入电子给体βtot值降低,且βtot值随取代基给电子能力的增强而减小.当分子变成相应的顺式结构时,其βtot值变化趋势与反式结构的结果正好相反.光异构化前后分子的βtot值变化不同,引入电子受体使顺式结构的βtot值比反式结构的小,其中―NO2使顺式结构的βtot值减小为反式结构的1/6;引入电子给体使反式结构的βtot值比顺式结构的小,其中―NH2使反式结构的βtot值减小为顺式结构的1/6.从而,光异构化起到调节非线性光学(NLO)响应的作用.     

Iodine as a mild, efficient, and cost-effective catalyst for the synthesis of thiiranes from oxiranes

We developed an efficient protocol for the synthesis of thiiranes from oxiranes using a catalytic amount of molecular iodine. The notable features of this procedure are mild reaction conditions, high conversions, short reaction times, economic viability of the reagents, compatibility with various functionalities, and simple experimental/product isolation procedures which make it a useful and attractive process for the synthesis of a range of thiiranes.     

PHOTOCHEMISTRY OF ALL-TRANS- AND 13-CIS-14,15-DIDEUTERIORETINAL

Abstract— All- trans - and 13- cis -14,15-dideuterioretinal were synthesized and their solution photochemistry examined. Quantum yields of trans → cis or cis → trans photoisomerization and the number and ratio of primary photoproducts, determined by high pressure liquid chromatographic analysis, are essentially identical to that of their corresponding retinal isomer. The C-14, C-15 carbon-hydrogen modes play no particularly important role in the deactivation of electronically excited linear polyenes related to retinal.     

Investigation of the Corey Bromolactamization with N‐Functionalized Allylamines

N‐Allylamines were employed for the diastereoselective synthesis of 8‐bromo‐substituted, cis‐configured perhydroquinoxalines and β‐bromoalcohols. The yield and constitution of the products depend considerably on the functionalization of the allylic N‐atom. Herein the reaction of glycine‐derived cyclohex‐2‐enamines 5 under bromolactamization conditions (LiOtBu, NBS) is reported. Methyl carbamate 5a led diastereoselectively to the cis‐configured perhydroquinoxaline 6a , whereas the amides 5b and 5c provided cis,trans‐configured ‐bromoalcohols 7b and 7c . Based on high level theoretical calculations (DFT) factors controlling the cyclization of lithiated intermediates and the relative energies of possible products are discussed.     

Overview of methods for the determination of trans fatty acids by gas chromatography, silver-ion thin-layer chromatography, silver-ion liquid chromatography, and gas chromatography/mass spectrometry

trans Isomers of naturally occurring cis-unsaturated fatty acids are produced when liquid vegetable oils or marine oils are partially hydrogenated to produce margarine, shortenings, and other hardened-fat products. Isomeric trans fatty acids are also formed in the intestinal tract of ruminants, and they appear in small amounts in dairy products and ruminant meat. Currently, satisfactory analyses for the fatty acid profiles of fats containing trans fatty acids are obtained by gas chromatography (GC) using capillary columns coated with highly polar cyanosilicone stationary phases. In capillary GC methods, the key limitation has been the incomplete separation of trans-monoenoic acid isomers from their cis isomers; however, recent reports have demonstrated that improvements in separation are attainable with the use of 100 m columns. In these columns, there is very little overlap of cis and trans isomers. More accurate trans fatty acid analyses can be obtained by coupling GC with either silver-nitrate thin-layer chromatography or silver-nitrate liquid chromatography.     

Reaction of thiiranes with azomethine compounds

Thiiranes add to imines and oximes to give thiazolidines. The addition of asymmetrical thiiranes is regioselective. The reaction of derivatives of asymmetrical carbonyl compounds with methylthiirane leads to mixtures of cis and trans stereoisomers of thiazolidines. In the N-arylideneethylamine series the reaction is accelerated by donor substituents and is retarded by acceptor substituents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 627–633, May, 1982.     

[(Polyfluoroalkoxy)methyl]thiiranes and 2-anilinoethanethiols

By reaction of appropriate oxiranes with thiourea [(polyfluoroalkoxy)methyl]-substituted thiiranes were obtained that are key compounds for the synthesis of perfluoro-containing 1,2-aminopropanethiols.     

Four ring achiral ferroelectric liquid crystals of 1,2,4-oxadiazoles: synthesis and characterisation

A novel series of four-ring achiral ferroelectric liquid crystals containing 1,2,4-oxadiazole cores with unsymmetrical substitutions at C-3 and C-5 positions are synthesised and characterised. A fluoro substituted biphenyl moiety is prepared by Suzuki coupling reaction and is directly attached to the oxadiazole core at the C-5 position for the first time in the literature. An octyl benzoate is attached to the oxadiazole core at the C-3 position of it. All the compounds exhibit polar smectic (B₂) mesophases with ferroelectric switching along with the orthogonal smectic-A mesophases. These compounds possess high mesomorphic thermal ranges of polar smectic phases and are towards the ambient temperatures. The influence of a more electronegative fluorine substituent on the electron rich biphenyl moiety (at the C-5 position) of the oxadiazole core is analysed for the prevalence and abundance of polar smectic (ferroelectric) mesophases.