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.

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.

scholarly journals SYNTHESIS OF 1,2;3,4-DI-O-ISOPROPYLIDENE-6- O-[4-(1H-AZOL-1-YLMETHYL) PHENYL]- ¯-D-GALACTOPYRANOSE AND 1,2,3,4-TETRA-O-ACETYL-6- O-[4-(1H-AZOL-1- YLMETHYL)PHENYL]-¯-D-GLUCOPYRANOSE

2017 ◽  
Vol 17 (5) ◽  
pp. 122-128
Author(s):  
Z.P. Belousova ◽  
P.P. Purygin ◽  
A.P. Tyurin
Keyword(s):  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Secondary Hydroxyl ◽  
Primary Hydroxyl ◽  
Derivatives Of

Derivatives of D-galactose and D-glucose substituted for the primary hydroxyl group, which contain an aglycone azolylmethylphenyl fragments (for imidazole, 1,2,4-triazole, benzimidazole and benzotriazole) has been synthesized. Toprotect the secondary hydroxyl groups of monosaccharides acetyl and isopropylidene groups were used.

scholarly journals Synthesis and fluorescence studies of novel bisarylmethylidene derivatives of 2-methoxy-2-methyl-1,3-dioxan-5-one

2017 ◽  
Vol 95 (7) ◽  
pp. 785-791
Author(s):  
Mohammad M. Mojtahedi ◽  
Kiana Darvishi ◽  
M. Saeed Abaee ◽  
Mohammad R. Halvagar
Keyword(s):  
Nmr Spectroscopy ◽  
Room Temperature ◽  
General Procedure ◽  
Photophysical Properties ◽  
Chromatographic Separations ◽  
X Ray ◽  
Fluorescence Studies ◽  
X Ray Crystallography ◽  
High Yields ◽  
Derivatives Of

The first general procedure is described for the synthesis of novel bisarylmethylidenes of 2-methoxy-2-methyl-1,3-dioxan-5-one 1. Thus, several derivatives of 3 are obtained rapidly in high yields by reacting 1 with different aldehydes in the presence of catalytic quantities of pyrrolidine in EtOH at room temperature. Upon completion of the reactions, products are obtained directly by spontaneous precipitation avoiding time consuming and expensive chromatographic separations. All products were characterized by proton and carbon NMR spectroscopy methods, and in one case, the proposed structure was elucidated by X-ray crystallography, confirming the Z stereochemistry for the olefinic C=C bonds. Due to showing different colours in solid and solution states, products were studied for their photophysical properties as well.

scholarly journals Tandem aldol condensation-Diels–Alder-aromatization sequence of reactions: a new pathway for the synthesis of 2-tetralone derivatives

2016 ◽  
Vol 94 (9) ◽  
pp. 733-737 ◽  
Author(s):  
M. Saeed Abaee ◽  
Esmail Doustkhah ◽  
Mohaddeseh Mohammadi ◽  
Mohammad M. Mojtahedi ◽  
Klaus Harms
Keyword(s):  
Room Temperature ◽  
Aldol Condensation ◽  
Diels Alder ◽  
One Pot ◽  
High Yields ◽  
Derivatives Of

A series of new polysubstituted derivatives of 2-tetralones possessing two ester groups were synthesized via a tandem aldol condensation-Diels–Alder-aromatization sequence of reactions. All the three steps took place in one pot and in the presence of aminofunctionalized silica coated Fe3O4 nanoparticles as the catalyst. In situ formed dienes reacted with diethyl acetylenedicarboxylate at room temperature and the process was followed by spontaneous aromatization of the cycloadducts to produce high yields of the final tetralone products. Further studies suggest that the process goes through an initial aldol condensation-cycloaddition sequence followed by oxidation and rearrangement steps. After completion of the reactions, the catalyst could be recycled and reused efficiently in subsequent reactions.

Development of the room temperature protocol based on room temperature ionic liquids and surfactant ionic liquids for the synthesis of derivatives of 2-amino-thiazoles and thermo-physical analysis of the synthesized derivatives using TGA-DSC.

2020 ◽  
Vol 10 ◽  
Author(s):  
Chandrakant Sarode ◽  
Sachin Yeole ◽  
Ganesh Chaudhari ◽  
Govinda Waghulde ◽  
Gaurav Gupta
Keyword(s):  
Thermal Analysis ◽  
Heat Capacity ◽  
Ionic Liquids ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Room Temperature ◽  
Heat Capacity Data ◽  
General Strategy ◽  
Capacity Data ◽  
Derivatives Of

Aims: To develop an efficient protocol, which involves an elegant exploration of the catalytic potential of both the room temperature and surfactant ionic liquids towards the synthesis of biologically important derivatives of 2-aminothiazole. Objective: Specific heat capacity data as a function of temperature for the synthesized 2- aminothiazole derivatives has been advanced by exploring their thermal profiles. Method: The thermal gravimetry analysis and differential scanning calorimetry techniques are used systematically. Results: The present strategy could prove to be a useful general strategy for researchers working in the field of surfactants and surfactant based ionic liquids towards their exploration in organic synthesis. In addition to that, effect of electronic parameters on the melting temperature of the corresponding 2-aminothiazole has been demonstrated with the help of thermal analysis. Specific heat capacity data as a function of temperature for the synthesized 2-aminothiazole derivatives has also been reported. Conclusion: Melting behavior of the synthesized 2-aminothiazole derivatives is to be described on the basis of electronic effects with the help of thermal analysis. Additionally, the specific heat capacity data can be helpful to the chemists, those are engaged in chemical modelling as well as docking studies. Furthermore, the data also helps to determine valuable thermodynamic parameters such as entropy and enthalpy.

The role of secondary alcoholic groups of D-galacturonan in its degradation with exo-D-galacturonanase

1980 ◽  
Vol 45 (2) ◽  
pp. 427-434 ◽  
Author(s):  
Kveta Heinrichová ◽  
Rudolf Kohn
Keyword(s):  
Acetyl Derivative ◽  
Competitive Inhibitor ◽  
Hydroxyl Groups ◽  
Pectic Acid ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
The Individual ◽  
Degradation Degree ◽  
Derivatives Of

The effect of exo-D-galacturonanase from carrot on O-acetyl derivatives of pectic acid of variousacetylation degree was studied. Substitution of hydroxyl groups at C(2) and C(3) of D-galactopyranuronic acid units influences the initial rate of degradation, degree of degradation and its maximum rate, the differences being found also in the time of limit degradations of the individual O-acetyl derivatives. Value of the apparent Michaelis constant increases with increase of substitution and value of Vmax changes. O-Acetyl derivatives act as a competitive inhibitor of degradation of D-galacturonan. The extent of the inhibition effect depends on the degree of substitution. The only product of enzymic reaction is D-galactopyranuronic acid, what indicates that no degradation of the terminal substituted unit of O-acetyl derivative of pectic acid takes place. Substitution of hydroxyl groups influences the affinity of the enzyme towards the modified substrate. The results let us presume that hydroxyl groups at C(2) and C(3) of galacturonic unit of pectic acid are essential for formation of the enzyme-substrate complex.

scholarly journals Synthesis of spiro[dihydropyridine-oxindoles] via three-component reaction of arylamine, isatin and cyclopentane-1,3-dione

2013 ◽  
Vol 9 ◽  
pp. 8-14 ◽  
Author(s):  
Yan Sun ◽  
Jing Sun ◽  
Chao-Guo Yan
Keyword(s):  
Acetic Acid ◽  
Reaction Mechanism ◽  
Room Temperature ◽  
The Other ◽  
Other Hand ◽  
Three Component Reaction ◽  
High Yields

A fast and convenient protocol for the synthesis of novel spiro[dihydropyridine-oxindole] derivatives in satisfactory yields was developed by the three-component reactions of arylamine, isatin and cyclopentane-1,3-dione in acetic acid at room temperature. On the other hand the condensation of isatin with two equivalents of cyclopentane-1,3-dione gave 3,3-bis(2-hydroxy-5-oxo-cyclopent-1-enyl)oxindole in high yields. The reaction mechanism and substrate scope of this novel reaction is briefly discussed.

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