scholarly journals Isolation of some precursors of 2-methylpyrrole in the Elson–Morgan reaction

1970 ◽  
Vol 120 (4) ◽  
pp. 873-876 ◽  
Author(s):  
Franca Serafini-Cessi ◽  
C. Cessi
Keyword(s):  
Acid Hydrolysis ◽  
Amino Group ◽  
Mild Conditions ◽  
Derivatives Of ◽  
Anhydrous Solvent

1-C-(1-Acetylacetonyl)-2-deoxy-2-(1-methyl-3-oxobut-1-enyl)amino -d-galactitol is obtained from the condensation of 2-amino-2-deoxy-d-galactose with pentane-2,4-dione in anhydrous solvent. On treatment with hot alkali it gives 2-methylpyrrole with 37% yield. By acid hydrolysis under mild conditions the compound loses the N substituent and from the resulting unstable derivative 2-methylpyrrole is obtained (52% yield). It is concluded that derivatives of aminohexoses substituted at C-1 with a dioxopentyl chain are the precursors of 2-methylpyrrole in the Cessi & Serafini-Cessi (1963) modification of the Elson–Morgan reaction. As demonstrated previously, products of condensation of aminohexoses with pentane-2,4-dione at the amino group are not converted directly into 2-methylpyrrole, but this step provides protection of the amino group during condensation at C-1.

Preparation of ketimine derivatives of amino acids for peptide synthesis

1974 ◽  
Vol 27 (9) ◽  
pp. 2047 ◽  
Author(s):  
B Halpern ◽  
AP Hope
Keyword(s):  
Amino Acids ◽  
Hydrogen Bond ◽  
Acid Hydrolysis ◽  
Peptide Synthesis ◽  
Room Temperature ◽  
Mild Conditions ◽  
Protein Amino Acids ◽  
Intramolecular Hydrogen ◽  
Derivatives Of ◽  
Strong Intramolecular Hydrogen Bond

Condensates of some 2-hydroxyaryl ketones with protein amino acids have been prepared. The reaction has been shown to proceed without racemization and the derivatives have been isolated as free acids. Their unusual stability is ascribed to the presence of a strong intramolecular hydrogen bond. The N-arylmethylene function is cleaved under mild conditions of acid hydrolysis. Ketimines derived from D-phenylglycine decarboxylate at room temperature.

scholarly journals The Fluoride Anion-Catalyzed Sulfurization of Thioketones with Elemental Sulfur Leading to Sulfur-Rich Heterocycles: First Sulfurization of Thiochalcones

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 822
Author(s):  
Grzegorz Mlostoń ◽  
Jakub Wręczycki ◽  
Katarzyna Urbaniak ◽  
Dariusz M. Bieliński ◽  
Heinz Heimgartner
Keyword(s):  
Elemental Sulfur ◽  
Fluoride Anion ◽  
Ring Size ◽  
Mild Conditions ◽  
Tetrabutylammonium Fluoride ◽  
Cesium Fluoride ◽  
Secondary Reactions ◽  
Derivatives Of

Fluoride anion was demonstrated as a superior activator of elemental sulfur (S8) to perform sulfurization of thioketones leading to diverse sulfur-rich heterocycles. Due to solubility problems, reactions must be carried out either in THF using tetrabutylammonium fluoride (TBAF) or in DMF using cesium fluoride (CsF), respectively. The reactive sulfurizing reagents are in situ generated, nucleophilic fluoropolysulfide anions FS(8−x)−, which react with the C=S bond according to the carbophilic addition mode. Dithiiranes formed thereby, existing in an equilibrium with the ring-opened form (diradicals/zwitterions) are key-intermediates, which undergo either a step-wise dimerization to afford 1,2,4,5-tetrathianes or an intramolecular insertion, leading in the case of thioxo derivatives of 2,2,4,4-tetramethylcyclobutane-1,3-dione to ring enlarged products. In reactions catalyzed by TBAF, water bounded to fluoride anion via H-bridges and forming thereby its stable hydrates is involved in secondary reactions leading, e.g., in the case of 2,2,4,4-tetramethyl-3-thioxocyclobutanone to the formation of some unexpected products such as the ring enlarged dithiolactone and ring-opened dithiocarboxylate. In contrast to thioketones, the fluoride anion catalyzed sulfurization of their α,β-unsaturated analogues, i.e., thiochalcones is slow and inefficient. However, an alternative protocol with triphenylphosphine (PPh3) applied as a catalyst, offers an attractive approach to the synthesis of 3H-1,2-dithioles via 1,5-dipolar electrocyclization of the in situ-generated α,β-unsaturated thiocabonyl S-sulfides. All reactions occur under mild conditions and can be considered as attractive methods for the preparation of sulfur rich heterocycles with diverse ring-size.

scholarly journals Optimized acid hydrolysis of the polysaccharides from the seaweed Solieria filiformis (Kützing) P.W. Gabrielson for bioethanol production

2017 ◽  
Vol 39 (4) ◽  
pp. 423 ◽  
Author(s):  
George Meredite Cunha de Castro ◽  
Norma Maria Barros Benevides ◽  
Maulori Curié Cabral ◽  
Rafael De Souza Miranda ◽  
Enéas Gomes Filho ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Sulfuric Acid ◽  
Acid Hydrolysis ◽  
Kinetic Parameters ◽  
Renewable Resource ◽  
Bioethanol Production ◽  
Seaweed Species ◽  
Mild Conditions ◽  
Hydrolysis Of ◽  
Solieria Filiformis

 The seaweeds are bio-resource rich in sulfated and neutral polysaccharides. The tropical seaweed species used in this study (Solieria filiformis), after dried, shows 65.8% (w/w) carbohydrate, 9.6% (w/w) protein, 1.7% (w/w) lipid, 7.0% (w/w) moisture and 15.9% (w/w) ash. The dried seaweed was easily hydrolyzed under mild conditions (0.5 M sulfuric acid, 20 min.), generating fermentable monosaccharides with a maximum hydrolysis efficiency of 63.21%. Galactose and glucose present in the hydrolyzed were simultaneously fermented by Saccharomyces cerevisiae when the yeast was acclimated to galactose and cultivated in broth containing only galactose. The kinetic parameters of the fermentation of the seaweed hydrolyzed were Y(P⁄S) = 0.48 ± 0.02 g.g−1, PP = 0.27 ± 0.04 g.L−1.h−1, h = 94.1%, representing a 41% increase in bioethanol productivity. Therefore, S. filiformis was a promising renewable resource of polysaccharides easily hydrolyzed, generating a broth rich in fermentable monosaccharides for ethanol production. 

scholarly journals Enantioenriched Quaternary α-Pentafluoroethyl Derivatives of Alkyl 1-Indanone-2-Carboxylates

2020 ◽  
Author(s):  
Albert Granados ◽  
Anna Balleteros ◽  
Adelina Vallribera
Keyword(s):  
Hypervalent Iodine ◽  
Catalytic Method ◽  
Quaternary Centers ◽  
Mild Conditions ◽  
Reaction Proceeds ◽  
Mechanistic Investigations ◽  
Derivatives Of

An electrophilic enantioselective catalytic method for the a-pentafluoroethylation of alkyl 1-indanone-2-carboxylates is described. Under the use of La(OTf)<sub>3</sub> in combination with (<i>S,R</i>)-indanyl-<i>pybox</i> ligand good results in terms of yield and enantioselectivities were achieved (up to 89% <i>ee</i>). The reaction proceeds under mild conditions leading to the formation of enantioenriched quaternary centers. This methodology uses an hypervalent iodine(III)-CF<sub>2</sub>CF<sub>3</sub> reagent and mechanistic investigations are consistent with the involvement of a radical pathway.

Exchange of the amino group in ?-amino derivatives of sulfolane

1974 ◽  
Vol 10 (5) ◽  
pp. 538-540
Author(s):  
T. �. Bezmenova ◽  
P. G. Dul'nev
Keyword(s):  
Amino Group ◽  
Amino Derivatives ◽  
Derivatives Of

N?-acyl derivatives of histidine with the di-(2-chloroethyl)amino group

1965 ◽  
Vol 14 (5) ◽  
pp. 888-890
Author(s):  
M. I. Dagene ◽  
L. P. Rasteikene ◽  
O. V. Kil'disheva ◽  
I. L. Knunyants
Keyword(s):  
Amino Group ◽  
Derivatives Of ◽  
Acyl Derivatives

4-N-Benzazolylamino Derivatives of 3-Y-3-Buten-2-one

1992 ◽  
Vol 57 (3) ◽  
pp. 531-539 ◽  
Author(s):  
Viktor Milata ◽  
Dušan Ilavský ◽  
Igor Goljer ◽  
Ján Leško
Keyword(s):  
Nucleophilic Substitution ◽  
Mass Spectra ◽  
Spectral Measurements ◽  
Mild Conditions ◽  
Derivatives Of ◽  
C Nmr

Ethoxymethylene derivatives of 2,4-pentanedione (Ia), 3-oxobutanenitrile (Ib), methyl (Ic) or ethyl (Id) 3-oxobutanoate give with 4- or 5-aminobenzimidazole or benzotriazole, respectively, under mild conditions products of nucleophilic substitution II-V. Structure of these compounds was discussed on the basis of their spectral measurements - IR, UV, 1H, 13C NMR and mass spectra.

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