Simplified synthesis of carbohydrate‐functional siloxanes via transacetalation. I. Glucose‐functional siloxanes

Carbohydrate‐functional siloxanes (CHFSs) that exhibit high intermolecular interactions and good environmental friendliness have successfully been synthesized by acid‐catalyzed transacetalation between an acetal‐functional siloxane and glucose in dimethylformamide/dioxane mixed solvents. Activated clay has proven to be a good catalyst because of its high activity and its easy removal from the product. Acetal‐functional siloxanes as starting materials can be easily synthesized in good yields by hydrosilylation between Si? H‐functional siloxanes and acrolein diethyl acetal. This method has the following advantages: (1) the inexpensive materials used, (2) the simplified process employed, and (3) the high yield achieved. Because the carbohydrate moieties in these materials have the nature of strong intermolecular interactions and are highly hydrophilic, CHFSs exhibit very high bulk viscosities in comparison with the corresponding acetal‐functional siloxanes and good solubilities in polar solvents such as dimethylformamide and dimethyl sulfoxide. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3336–3345, 2003     

A one-step oxidative synthesis of trimethylantimony(v) diacylates

Trimethylantimony(v) diacylates Me₃Sb(OCOR)₂ (R = H, Me, Ph) have been obtained in 72–75 % yield by the interaction of trimethylantimony withtert-butylhydroperoxide and carboxylic acids at the ratio of 1 1 2 in benzene (20 °C, 20 h) in the presence of sodium sulfate.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 537–538, March, 1994.     

Efficient synthesis of phosphonodepsipeptides derived from norleucine

In the present work, we describe in detail an efficient solution synthesis of norleucine-derived phosphonopeptides mimicking the peptide sequences Nle-Gly(Ala) and Nle-Gly(Ala)-Val. The most efficient strategy involved use of the benzyl group. The synthesis was achieved through BOP-catalysed coupling of the monobenzyl ester of the N-Cbz-protected phosphonate derivative of norleucine with the hydroxyl moieties of derivatised l-lactic or glycolic acid. Subsequently, complete deprotection of the products was achieved in good yields by one-step Pd-catalysed hydrogenolysis. We also prepared the Fmoc-Nle-Ψ[PO(OH)O]-CH₂-COOH synthon and demonstrated that this precursor is a suitable building block for the solid-phase synthesis of cysteine-containing phosphonopeptides.     

Facile synthesis of phenyl-rich functional siloxanes from simple silanes

Phenyl-rich silicone polymers are used for their excellent thermal properties and high refractive indices. Traditional syntheses of these polymers utilize cationic or anionic equilibration, which limits the molecular weights that can be achieved due, in part, to the coproduction of cyclic monomers that must be removed. Kinetically controlled processes may reduce the impact of these limitations, but require high temperatures, alkyllithium initiators and an inert atmosphere; precise structures are difficult to access. The Piers-Rubinsztajn reaction, combined with hydrolysis, allows the synthesis of highly ordered, Si-H terminated, phenyl-rich silicone homo- and copolymers comprised of phenylmethyl, diphenyl and, dimethylsilicone monomers. The processes are mild and permit a high level of structural control, including alternating copolymers with different levels of phenyl content (Ph/Si = 0.3–1.5) with molecular weights up to ~100 kDa. Yet higher molecular weights could be achieved—M_n up to 300 kDa—when phenyl-rich siloxanes were incorporated into block copolymers with dimethylsilicones (Ph/Si = 0.4). Unlike kinetic processes in which cyclic byproducts are formed by redistribution or backbiting (particularly at high conversion), in this process cyclics form near the onset of the reaction and only with low molecular weight starting materials (< 4 siloxane units).     

Chemoselective hydrosilations. I. Synthesis and photopolymerization of 1-propenyl ether functionalized siloxanes

The synthesis of 1-propenyl ether-functionalized siloxanes (PFS) has been achieved by the controlled, rhodium-catalyzed, chemoselective hydrosilation of 1-allyloxy-4(1-propen-oxy) butane with various H-functional siloxanes. It was shown that the hydrosilation pro-ceeds exclusively at the allyl ether group of 1-allyloxy-4(1-propenoxy) butane without par-ticipation at the 1-propenyl ether group. The photoinduced cationic polymerization of these monomers was studied using various analytical techniques and found to take place very rapidly. © 1995 John Wiley & Sons, Inc.     

Facile route to synthesis of functionalised poly(methylalkoxy)siloxane under mild and aerobic conditions in the presence of platinum catalysts

A facile and high yield method of synthesis of novel and functional poly(methylalkoxy) siloxanes is reported. The Si–H groups of poly(methylhydrogen) siloxanes (PMHS) were treated with various simple (primary, secondary, tertiary) alcohols (1a–10a) in the presence of platinum based catalysts (Speier’s and Karstedt’s catalysts). Also oxyethylene, aldehyde, epoxide, halogen and allyl grafted polysiloxane were smoothly and quantitatively prepared by the alcoholysis between linear siloxanes polymer and functional alcohols (11a–20a) with use of Karstedt’s catalysts. It is found that alcoholysis reaction in the presence of the Karstedt’s catalyst proceed faster than Speier’s catalyst .In addition, the rate of alcoholysis reaction is dependent on amount of the catalyst and reaction temperature. The polymers prepared were characterized by IR, NMR spectroscopy and GPC analysis.     

New preparative Grignard synthesis of (m-carboranylmethyl)siloxanes from chlorodimethylsiloxanes

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A practical stereoselective synthesis of (S)-( - )-ofloxacin

A very efficient and practical procedure for preparation of ( S)-( - )-ofloxacin has been developed (10 steps, overall yield ≥ 45 % ) . The key step of this approach is the regioselective nucleophilic substitution of 2-position fluorine atom of 2,3,4-tirfluoronitrobenzene by (S)-glycerol acetonide.     

Efficient (bromodimethyl)sulfonium bromide mediated synthesis of benzimidazoles

Benzimidazoles have been efficiently synthesized in high yields by treatment of 1,2-phenylenediamine with aldehydes using (bromodimethyl)sulfonium bromide at room temperature.     

Efficient synthesis of 2-(pyrazol-3-yl)benzimidazoles from 3-arylacylidene-3,4-dihydroquinoxalin-2(1H)-ones and hydrazine hydrate via a novel rearrangement

A highly efficient method for the synthesis of 2-(pyrazol-3-yl)benzimidazoles has been developed on the basis of the novel ring contraction of 3-arylacylidene-3,4-dihydroquinoxalin-2(1H)-ones with hydrazine hydrate.     

Efficient and improved synthesis of triazole-linked DNA (DNA) oligomers

A method for the synthesis of triazole-linked DNA oligomers has been revisited to incorporate a reliable protective group and linker for solid-phase synthesis. The new solid-phase synthesis allowed the preparation of oligomers with the efficiency of elongation reaching over 90%.     

Efficient synthesis of some 3-arylisoquinolin-1(2H)-ones

A number of 3-arylisoquinolin-1(2H)-ones were efficiently prepared from the corresponding 3-aryl-isocoumarins by refluxing with methanamide. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1203–1208, August, 2008.     

A facile one‐pot synthesis of [(COD)Pt(CH3)2]

A novel one‐pot synthesis of dimethyl(1,5‐cyclooctadiene)platinum(II), i.e. [(COD)Pt(CH₃)₂] (complex 1), was developed in 92% yield using platinum acetylacetonate, 1,5‐cyclooctadiene and trimethylaluminium. Complex 1 was fully characterized by ¹H and ¹³C NMR, mass spectrometry, cell dimensions and elemental analysis. Copyright © 2005 John Wiley & Sons, Ltd.     

Molecular structure of (3,5-diallylisocyanuratomethyl)bis(chloromethyl)phosphine oxide. Synthesis of (3,5-diallylisocyanuratomethyl)phosphine sulfides

X-Ray study of the (3,5-diallylisocyanuratomethyl)bis(chloromethyl)phosphine oxide showed that the phosphorylmethyl group is bonded to the nitrogen atom of the cycle. Reaction of the tris(chloromethyl)phosphine sulfide with sodium diallylisocyanurate gave (3,5-diallylisocyanuratomethyl)bis(chloromethyl)phosphine sulfide, and treatment of the tris(3,5-diallylisocyanuratomethyl)phosphine oxide with phosphorus pentasulfide gave a tris(3,5-diallylisocyanuratomethyl)bis(chloromethyl)phosphine sulfide.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1446–1448, August, 1993.     

Efficient synthesis of 4(3H)-quinazolinones using a soluble polymeric support

4(3H)-Quinazolinones have been synthesized from poly(ethylene glycol)(PEG)supported aza-Wiuig reaction.2-Dialkylamino- 4(3H)-quinazolinones 6 were synthesized efficiently by reaction of secondary amine with PEG-supported carbodiimides 4,which were obtained from aza-Wittig reaction of PEG-supported iminophosphoranes 3 with isocyanates.     

Efficient one-pot synthesis of diphenyl(pyrazin-2-yl)phosphine and its AgI,AuI and PtII complexes

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无溶剂条件下对甲基苯磺酸铝高效催化合成4,6-二芳基-3,4-二氢嘧啶-2(1H)-酮

以芳香醛、芳香酮和尿素为原料,对甲基苯磺酸铝为催化剂,在90_oC、无溶剂条件下“一锅法”反应,高效合成了一系列4,6-二芳基-3,4-二氢嘧啶-2(1H)-酮。产品结构通过IR,₁H NMR,₁₃C NMR和元素分析进行了表征。该方法具有操作简单、反应时间短、产率高、反应条件温和、不使用任何有机溶剂、催化剂廉价易得且可重复使用等优点,为标题化合物的合成提供了一种简便高效的绿色新途径。     

Poly(silarylene–siloxane)polyimides from allyl‐terminated oligoimides and hydride‐functional silarylene–siloxanes via hydrosilylation polymerization

This research was focused on the design and execution of new synthetic routes to low‐temperature‐curable poly(silarylene–siloxane)polyimides. The synthesis of individual oligoimide and silarylene–siloxane blocks was followed by hydrosilylation polymerization to produce crosslinked copolymers. The silarylene–siloxane and polyimide blocks were structurally characterized by IR and ¹H NMR spectroscopy and size exclusion chromatography. The high‐temperature resistance of the copolymers was evaluated through the measurement of heat distortion temperatures (T_HD's) via thermomechanical analysis and by the determination of the weight loss at elevated temperatures via thermogravimetric analysis. Glass‐transition temperatures (T_g's) of the silarylene–siloxane segments were measured by differential scanning calorimetry. Hydrosilylation curing was conducted at 60 °C in the presence of chloroplatinic acid (H₂PtCl₆). The copolymers displayed both high‐temperature resistance and low‐temperature flexibility. We observed T_g of the silarylene–siloxane segment as low as ?77 °C and T_HD of the polyimide segment as high as 323 °C. The influence of various oligoimide molecular weights on the properties of copolymers containing the same silarylene–siloxane was examined. The effect of various silarylene–siloxane molecular weights on the properties of copolymers containing the same oligoimide was also examined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4922–4932, 2005