Conversion of hydroxyl groups into bromo groups in carbohydrates with inversion of configuration

1981 ◽  
Vol 59 (2) ◽  
pp. 339-343 ◽  
Author(s):  
Björn Classon ◽  
Per J. Garegg ◽  
Bertil Samuelsson
Keyword(s):  
Elevated Temperature ◽  
Hydroxyl Groups ◽  
Secondary Hydroxyl ◽  
Reaction Proceeds ◽  
One Step ◽  
High Yields

A novel reagent system is described for the efficient, one-step transformation of hydroxyl groups in carbohydrates to bromodeoxy groups. The reaction proceeds with inversion of configuration. The reagent system consists of triphenylphosphine, tribromoimidazole, and imidazole in toluene at elevated temperature. The carbohydrate need not be soluble in toluene. The examples given include substitution of isolated primary and secondary hydroxyl groups in otherwise protected carbohydrates as well as disubstitution involving one primary and one secondary position in hexopyranosides. High yields are obtained in the replacement of hydroxyl by bromine in the 2-position of 3,4,6-protected methyl α-D-gluco- and -mannopyranosides.

Hypophosphite Addition to Alkenes Under Solvent-Free and Non-Acidic Aqueous Conditions

2022 ◽  
Author(s):  
Zhaorui Huang ◽  
Yuxuan Chen ◽  
Matthew Kanan
Keyword(s):  
Elevated Temperature ◽  
Solvent Free ◽  
Solvent Free Conditions ◽  
Reaction Proceeds ◽  
High Yields ◽  
Aqueous Conditions

Hypophosphite adds to alkenes in high yields under solvent-free conditions at elevated temperature, including ,-unsaturated carboxylates. The reaction proceeds by a radical mediated pathway. Hypophosphite addition is also effective under...

Kinetic benzylidenation. Part II. Rearrangement of the kinetic products from benzylidenation of aldose diethyl dithioacetals

1986 ◽  
Vol 64 (12) ◽  
pp. 2397-2403 ◽  
Author(s):  
T. Bruce Grindley ◽  
Srihari Kusuma
Keyword(s):  
Room Temperature ◽  
Hydroxyl Groups ◽  
Secondary Hydroxyl ◽  
High Yields ◽  
Derivatives Of

Terminal five-membered O-benzylidene derivatives of aldose diethyl dithioacetals can be rearranged at room temperature in N,N-dimethylformamide, often in high yields. Derivatives with the arabino configuration for their three terminal secondary hydroxyl groups, i.e. D-glucose, D-mannose, and D-arabinose derivatives, rearranged to structures containing terminal six-membered O-benzylidene rings. 4,5-O-Benzylidene-D-ribose diethyl dithioacetal rearranged chiefly to the 2,4 isomer, which was obtained by crystallization. Chromatography yielded some of the 3,5 isomer. 5,6-O-Benzylidene-D-galactose diethyl dithioacetal rearranged to a mixture of the two 4,5-O-benzylidene diastereomers, contrary to predictions based on the Hann–Hudson rules. A revised set of rules for acetal stability in N,N-dimethylformamide has been formulated. D-arabinose and D-ribose diethyl dithioacetal were shown to react with α, α-dimethoxytoluene under rearrangement conditions to give the products noted above in good yields.

An Efficient Direct Access to Carbamates from Alcohols and TosMIC Mediated by Iodine in DMSO

Synlett ◽  
2018 ◽  
Vol 29 (15) ◽  
pp. 2039-2042 ◽  
Author(s):  
Y. Prapurna ◽  
Naresh Pogaku ◽  
Palakodety Krishna
Keyword(s):  
Direct Access ◽  
New Approach ◽  
Mild Conditions ◽  
Rapid Construction ◽  
Practical Strategy ◽  
Dmso System ◽  
Reaction Proceeds ◽  
One Step ◽  
High Yields

A new approach for the synthesis of carbamates from alcohols and TosMIC promoted by iodine/DMSO system is reported. This method offers a one-step, direct and practical strategy for the rapid construction of carbamates under mild conditions. The reaction proceeds via sequential oxidation of isocyanide to isocyanate and nucleo­philic addition of alcohols to isocyanate to afford the carbamates in high yields.

scholarly journals PEG-embedded KBr3: A recyclable catalyst for multicomponent coupling reaction for the efficient synthesis of functionalized piperidines

2011 ◽  
Vol 7 ◽  
pp. 1334-1341 ◽  
Author(s):  
Sanny Verma ◽  
Suman L Jain ◽  
Bir Sain
Keyword(s):  
Coupling Reaction ◽  
Recyclable Catalyst ◽  
Efficient Synthesis ◽  
Molecular Bromine ◽  
Keto Ester ◽  
One Step ◽  
High Yields ◽  
Multicomponent Coupling ◽  
Three Component Coupling

PEG-embedded potassium tribromide ([K+PEG]Br3 −) was found to be an efficient and recyclable catalyst for the synthesis of functionalized piperidines in high yields in a one step, three component coupling between aldehyde, amine and β-keto ester. At the end of the reaction the [K+PEG]Br3 − was readily regenerated from the reaction mixture by treating the residue containing [K+PEG]Br− with molecular bromine.

Regioselectivity among six secondary hydroxyl groups: selective acylation of the least reactive hydroxyl groups of inositol

2012 ◽  
Vol 48 (18) ◽  
pp. 2448 ◽  
Author(s):  
Amol M. Vibhute ◽  
Adiyala Vidyasagar ◽  
Saritha Sarala ◽  
Kana M. Sureshan
Keyword(s):  
Hydroxyl Groups ◽  
Secondary Hydroxyl ◽  
Selective Acylation

scholarly journals Amphiphilic Biaryl Monophosphine Ligands by Regioselective Sulfonation

2020 ◽  
Author(s):  
Jacob Rodriguez ◽  
Heemal Dhanjee ◽  
Stephen L. Buchwald
Keyword(s):  
Sulfuric Acid ◽  
Chromatographic Purification ◽  
Organometallic Reactions ◽  
One Step ◽  
High Yields

<div> <p>Amphiphilic ligands are valued for their ability to facilitate organometallic reactions in the presence of water. The regioselective sulfonation of a series of commercially available biaryl monophosphines to generate amphiphilic ligands is presented. In this one-step protocol, the temperature and addition of fuming sulfuric acid were carefully controlled to arrive at sulfonated biaryl monophosphine ligands in high yields with >95% regioselectivity without the need for chromatographic purification.</p> </div>

scholarly journals New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

2015 ◽  
Vol 11 ◽  
pp. 1175-1186 ◽  
Author(s):  
Rym Hassani ◽  
Mahjoub Jabli ◽  
Yakdhane Kacem ◽  
Jérôme Marrot ◽  
Damien Prim ◽  
...  
Keyword(s):  
Optical Properties ◽  
Spectroscopic Analysis ◽  
Palladium Complexes ◽  
X Ray Diffraction ◽  
Factors Affecting ◽  
Enantiomerically Pure ◽  
One Step ◽  
Uv Visible ◽  
High Yields

The present paper describes the synthesis of new palladium–oxazoline complexes in one step with good to high yields (68–95%). The oxazolines were prepared from enantiomerically pure α-aminoalcohols. The structures of the synthesized palladium complexes were confirmed by NMR, FTIR, TOFMS, UV–visible spectroscopic analysis and X–ray diffraction. The optical properties of the complexes were evaluated by the determination of the gap energy values (E g) ranging between 2.34 and 3.21 eV. Their catalytic activities were tested for the degradation of Eriochrome Blue Black B (a model of azo dyes) in the presence of an ecological oxidant (H2O2). The efficiency of the decolorization has been confirmed via UV–visible spectroscopic analysis and the factors affecting the degradation phenomenon have been studied. The removal of the Eriochrome reached high yields. We have found that the complex 9 promoted 84% of color elimination within 5 min (C 0 = 30 mg/L, T = 22 °C, pH 7, H2O2 = 0.5 mL) and the energetic parameters have been also determined.

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