A novel approach to carbohydrate clusters: the regioselective synthesis of non-glycosidically linked oligosaccharides

1997 ◽  
Vol 75 (7) ◽  
pp. 983-995 ◽  
Author(s):  
Hassan Namazi ◽  
T. Bruce Grindley
Keyword(s):  
Room Temperature ◽  
Membered Ring ◽  
Regioselective Synthesis ◽  
Tertiary Amines ◽  
Excellent Yield ◽  
Novel Approach ◽  
Reaction Stoichiometry ◽  
Cis And Trans ◽  
Acylation Reactions

Dialkylstannylene acetals derived from a number of different carbohydrates having both cis- and trans-1,2-diols free were reacted with diacyl chlorides and disulfonyl chlorides in the presence of tertiary amines at room temperature to give symmetrical non-glycosidically linked disaccharides with excellent regioselectivity and in excellent yield. The regioselectivity obtained was the same as that previously found in acylation reactions of the same substrates. In one case, a symmetric non-glycosidically linked diasaccharide was also obtained in excellent yield. For methyl 4,6-O-benzylidene-α-D-glucopyranoside, a 16-membered ring macrocyclic tetralactone was obtained in 50% yield by altering the reaction stoichiometry and performing the reaction at 80 °C. Keywords: carbohydrates, clusters, non-glycosidically linked oligosaccharides, disaccharides, trisaccharides.

Synthesis of 1,1-diacetates from Aromatic Aldehydes using Cerium(IV) Sulfate Tetrahydrate as Catalyst under Solvent-free Conditions

2005 ◽  
Vol 2005 (3) ◽  
pp. 171-172 ◽  
Author(s):  
Min Zhang ◽  
Yi-Qun Li
Keyword(s):  
Room Temperature ◽  
Aromatic Aldehydes ◽  
Solvent Free ◽  
Excellent Yield ◽  
Solvent Free Conditions

Aromatic aldehydes can be converted into the corresponding 1,1-diacetates rapidly in the presence of catalytic amounts of Ce(SO4)2·4H2O at room temperature in excellent yield under solvent-free conditions. The catalyst can easily be recovered and reused at least 4 times.

scholarly journals Silylated gallium and indium chalcogenide ring systems as potential precursors to ME (E=O, S) materials

2013 ◽  
Vol 11 (7) ◽  
pp. 1225-1238
Author(s):  
Iliana Medina-Ramírez ◽  
Cynthia Floyd ◽  
Joel Mague ◽  
Mark Fink
Keyword(s):  
Thermal Decomposition ◽  
Room Temperature ◽  
Membered Ring ◽  
Molecular Structures ◽  
Nmr Studies ◽  
X Ray ◽  
X Ray Crystallography ◽  
High Yields ◽  
Vt Nmr ◽  
State 1

AbstractThe reaction of R3M (M=Ga, In) with HESiR′3 (E=O, S; R′3=Ph3, iPr3, Et3, tBuMe2) leads to the formation of (Me2GaOSiPh3)2(1); (Me2GaOSitBuMe2)2(2); (Me2GaOSiEt3)2(3); (Me2InOSiPh3)2(4); (Me2InOSitBuMe2)2(5); (Me2InOSiEt3)2(6); (Me2GaSSiPh3)2(7); (Et2GaSSiPh3)2(8); (Me2GaSSiiPr3)2(9); (Et2GaSSiiPr3)2(10); (Me2InSSiPh3)3(11); (Me2InSSiiPr3)n(12), in high yields at room temperature. The compounds have been characterized by multinuclear NMR and in most cases by X-ray crystallography. The molecular structures of (1), (4), (7) and (8) have been determined. Compounds (3), (6) and (10) are liquids at room temperature. In the solid state, (1), (4), (7) and (9) are dimers with central core of the dimer being composed of a M2E2 four-membered ring. VT-NMR studies of (7) show facile redistribution between four- and six-membered rings in solution. The thermal decomposition of (1)–(12) was examined by TGA and range from 200 to 350°C. Bulk pyrolysis of (1) and (2) led to the formation of Ga2O3; (4) and (5) In metal; (7)–(10) GaS and (11)–(12) InS powders, respectively.

Regioselective synthesis of functionalized dihydroisoquinolines from o-alkynylarylaldimines via the Reformatsky reaction

2016 ◽  
Vol 14 (41) ◽  
pp. 9896-9906 ◽  
Author(s):  
Tohasib Yusub Chaudhari ◽  
Urvashi Urvashi ◽  
Sandeep K. Ginotra ◽  
Pooja Yadav ◽  
Gulshan Kumar ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Regioselective Synthesis ◽  
Reformatsky Reaction ◽  
Novel Approach ◽  
The Reformatsky Reaction

A novel approach for the synthesis of functionalized 1,2-dihydroisoquinolines from o-alkynylarylaldimines via the Reformatsky reaction without the aid of an external Lewis acid has been described.

scholarly journals Photochemische Reaktionen von Übergangsmetall-Olefin-Komplexen, V [1]. Die Umsetzung von Tricarbonyl-η-6.6-dimethylfulven-chrom(0) mit 7-Methyl- und 7-Methoxycycloheptatrien / Photochemical Reactions of Transition Metal Olefin Complexes, V [1]. The Reactions of Tricarbonyl-η-6,6-dimethylfulvene-chromium(0) with 7-Methyl- and 7-Methoxycycloheptatriene

1982 ◽  
Vol 37 (10) ◽  
pp. 1322-1326 ◽  
Author(s):  
Cornelius G. Kreiter ◽  
Hans Kurz
Keyword(s):  
Nmr Spectroscopy ◽  
Transition Metal ◽  
Column Chromatography ◽  
Room Temperature ◽  
Photochemical Reactions ◽  
Membered Ring ◽  
Reaction Products ◽  
Methyl Group

Abstract The stereochemistry of the photo reaction products of tricarbonyl-η-6,6-dimethyl-fulvene-chromium(O) (1) with 7-methyl-and 7-methoxycycloheptatriene was studied by NMR-spectroscopy. Both trienes add to 1, displace a CO ligand, and form substituted dicarbonyl-η3-2-cycloheptadienylene-η5-2-cyclopentadienylidene-propane-chromium(0) complexes. With C7H7CH3 only one isomer (3) is formed with the methyl-group in endo-position and the enyl system encompassing C(1′)-C(3′) of the seven membered ring. C7H7OCH3 yields 3 isomers which were separated by column chromatography. 5 has the same constitution as 3. The isomers 4 and 5 bear the OCH3-group in e^o-position. The enyl system of 4 is located on C(1′)-C(3′), that of 6 on C(3′)-C(5′). 6 rearranges at room temperature to 4.

scholarly journals Low Temperature Chemoselective Hydrogenation of Aldehydes over a Magnetic Pd Catalyst

2019 ◽  
Vol 9 (9) ◽  
pp. 1792
Author(s):  
Liu ◽  
Wang ◽  
Gao ◽  
Wang ◽  
Cheng ◽  
...  
Keyword(s):  
Low Temperature ◽  
Room Temperature ◽  
Heterogeneous Catalysts ◽  
Aromatic Aldehydes ◽  
Pd Catalyst ◽  
Primary Alcohols ◽  
Mild Conditions ◽  
Excellent Yield ◽  
Chemoselective Hydrogenation ◽  
Supported Palladium

Chemoselective hydrogenation of aldehydes with heterogeneous catalysts under mild conditions is of great importance but remains a major challenge. Herein, an efficient strategy was developed for low temperature chemoselective hydrogenation of aldehydes with broad substrate scope over a magnetic material supported palladium catalyst (γ-Fe2O3@HAP-Pd). Aldehydes bearing various reducible functional groups readily underwent hydrogenation to give the corresponding primary alcohols with moderate to excellent yield at room temperature in aqueous solutions. The Hammett equation revealed that the hydrogenation of aromatic aldehydes proceeded via an anionic intermediate. Additionally, when the temperature increased to 70 °C, toluene was obtained by the deoxygenation of benzaldehyde in excellent yield. Furthermore, the γ-Fe2O3@HAP-Pd could be recycled up to six times without loss of activity and metal leaching.

Das dynamische Verhalten des 1-Methyl-1-benzothiepinium-Ringsystems/The Dynamic Behaviour of the 1-Methyl-1-benzothiepinium Ring System

1981 ◽  
Vol 36 (8) ◽  
pp. 974-977 ◽  
Author(s):  
Hans Hofmann ◽  
Franz Dickert
Keyword(s):  
Nmr Spectroscopy ◽  
Room Temperature ◽  
Dynamic Behaviour ◽  
Ring System ◽  
Membered Ring ◽  
Ring Inversion ◽  
Methyl Group ◽  
H Nmr ◽  
Pyramidal Inversion ◽  
Mutual Conversion

Abstract By 1H NMR spectroscopy the stereochemistry of the 1-methyl-1-benzothiepinium ring system was investigated both in thermodynamic and kinetic respects. It was shown that in solution a rapid mutual conversion of the boat shaped seven membered ring system with exo-respectively endo-S-methyl group occurs via a ring inversion and not by a pyramidal inversion at the sulfonium ion. At room temperature predominantly the conformation with the exo-S-methyl group is present.

Solvent-free and room temperature visible light-induced C–H activation: CdS as a highly efficient photo-induced reusable nano-catalyst for the C–H functionalization cyclization of t-amines and C–C double and triple bonds

2018 ◽  
Vol 20 (24) ◽  
pp. 5540-5549 ◽  
Author(s):  
Somayeh Firoozi ◽  
Mona Hosseini-Sarvari ◽  
Mehdi Koohgard
Keyword(s):  
Visible Light ◽  
Room Temperature ◽  
Solvent Free ◽  
Tertiary Amines ◽  
Triple Bonds ◽  
Highly Efficient ◽  
Nano Catalyst

Nano-sized CdS was successfully prepared, fully characterized and applied as a highly efficient reusable photocatalyst for the condensation of tertiary amines with double and triple bonds via a C–H activation approach.

scholarly journals Oxidation of geraniol using niobia modified with hydrogen peroxide

2019 ◽  
Author(s):  
Jairo Cubillos ◽  
José J. Martínez ◽  
Hugo Rojas ◽  
Norman Marín-Astorga
Keyword(s):  
Hydrogen Peroxide ◽  
Transition State ◽  
Kinetic Data ◽  
Room Temperature ◽  
Membered Ring ◽  
Morphological Properties ◽  
Peroxo Complex ◽  
Complex Species ◽  
Ring Transition State

Nb2O5 bulk and Nb2O5 modified with H2O2 were studied in the epoxidation of geraniol at 1 bar and room temperature. The structural and morphological properties for both catalysts were very similar, indicating that the peroxo-complex species were not formed. The order of the reaction was one respect to geraniol and close to zero respect to H2O2, these values fit well with the kinetic data obtained. The geraniol epoxidation is favored by the presence of peroxo groups, which is reached using an excess of H2O2. Moreover, the availability of the geraniol to adopt the three-membered-ring transition state was found as the best form for this type of compound.

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