scholarly journals Pyridine-Imidazlolium Salts: Oxidatively Cleavage of N-C Bond via Nitration

Molbank ◽  
10.3390/m1095 ◽  
2019 ◽  
Vol 2019 (4) ◽  
pp. M1095
Author(s):  
Dumitrela Cucu (Diaconu) ◽  
Violeta Mangalagiu
Keyword(s):  
Sulphuric Acid ◽  
Medicinal Chemistry ◽  
Oxidative Cleavage ◽  
Imidazolium Ring ◽  
Methylene Group

Azaheterocycles derivatives with pyridine-imidazole skeleton are compounds of great value for medicinal chemistry. We report herein the nitration of 1,1′-(pyridine-2,6-diylbis(methylene))bis{3-[2-(4-nitrophenyl)-2-oxoethyl]-1H-imidazol-3-ium} bromide using a typical mixture of nitric and sulphuric acid. The nitration occur with the oxidative cleavage of N–C bond between imidazolium ring and methylene group.

STUDIES IN THE POLYOXYPHENOL SERIES: IX. THE SYNTHESIS OF PAPAVERINE AND PAPAVERALDINE BY THE POMERANZ-FRITSCH METHOD

1955 ◽  
Vol 33 (5) ◽  
pp. 729-742 ◽  
Author(s):  
Donald A. Guthrie ◽  
Arlen W. Frank ◽  
C. B. Purves
Keyword(s):  
Sulphuric Acid ◽  
Acetyl Derivative ◽  
Mercury Complex ◽  
Crude Product ◽  
Group A ◽  
Methylene Group

Fritsch's cyclization of N-(α-veratrylveratrylidene)-aminoacetal in sulphuric acid was shown to give 1.1% of papaverine and 23% of an isomer, m.p. 164.5–165.5 °C.; hydrochloride, m.p. 212 °C. decomp., which was supposed to be 4,5-bis(3,4-dimethoxyphenyl)-2H-pyrrolenine, produced by an internal condensation of the acetal or the corresponding aldehyde with the reactive methylene group. A similar structure was proposed for another unidentified isomer prepared by Schlittler and Müller. Hydrogenation of Fritsch's acetal gave N-(α-veratryl-veratryl)-aminoacetal, m.p. 69.5–70 °C., which was cyclized to a base, m.p. 155.5–156 °C.; N-acetyl derivative, m.p. 203.5–204 °C., formulated as 2,3-bis(3,4-dimethoxyphenyl)-3-pyrroline. Substances presumed to be the intermediate aldehyde and aldol were isolated as colorless oils. Condensation of the diketone veratril with aminoacetal, followed by cyclization of the crude product, constituted a new two-step synthesis of papaveraldine in 8% yield, and the reduction of the latter to papaverine was known.Other crystalline compounds prepared incidentally and thought to be new were veratril monoanil, m.p. 172–173 °C.; α,α′-biveratrylideneaminoacetal, m.p. 101–102 °C.; a compound formulated as 2,3-bis(3,4-dimethoxyphenyl)-4-ethylmer-captopyrrolidine hydrochloride, m.p. 184–185 °C; from this an unidentified mercury complex, m.p. 109 °C. decomp.; 4,4′dibenzyloxy-3,3′-dimethoxy-desoxybenzoin, m.p. 141–142 °C; and its oxime, m.p. 137.5 °C.

scholarly journals A 13C-n.m.r. investigation of ionizations within a trypsin-inhibitor complex. Evidence that the pKa of histidine-57 is raised by interaction with the hemiketal oxyanion

1985 ◽  
Vol 231 (3) ◽  
pp. 677-682 ◽  
Author(s):  
W U Primrose ◽  
A I Scott ◽  
N E Mackenzie ◽  
J P G Malthouse
Keyword(s):  
Mechanism Of Action ◽  
Trypsin Inhibitor ◽  
Serine Proteinases ◽  
Inhibitor Complex ◽  
Imidazolium Ring ◽  
Imidazolium Ion ◽  
Methylene Group

The 13C-n.m.r. titration shifts of the α-methylene group of N-alkylated imidazoles are shown to be a sensitive probe of the ionization of the imidazolium ion. The 13C-n.m.r. titration shifts of both the intact and denatured/autolysed 2-13C- and 1-13C-enriched trypsin-7-amino-3-benzyloxycarbonylamino-1-chloroheptan-2-one (Z-Lys-CH2Cl) complexes are compared. The titration shift for the denatured/autolysed complex confirms that this ionization is due to deprotonation of the N-alkylated imidazolium ring of histidine-57. In the intact trypsin-inhibitor complex the titration shift due to the 1-13C-enriched carbon is anomalous. We conclude that this titration shift cannot arise solely from the ionization of the imidazolium ion of histidine-57 and that the pKa of the imidazolium ion of histidine-57 is raised in the trypsin-inhibitor complex. The relevance of these studies to the mechanism of action of the serine proteinases is discussed.

The Alkaloids of Crotalaria goreensis Guill. et Perr.: 7β-Hydroxy-1-methylene-8β- and 7β-Hydroxy-1-methylene-8α-pyrrolizidine

1961 ◽  
Vol 14 (2) ◽  
pp. 284 ◽  
Author(s):  
CCJ Culvenor ◽  
LW Smith
Keyword(s):  
Sulphuric Acid ◽  
Absolute Configuration ◽  
Main Product ◽  
The Other ◽  
Relative Configuration ◽  
Minor Alkaloid ◽  
Methylene Group

The principal alkaloid of Crotalaria goreensis Guill. et Perr. is 7β-hydroxy-1-methylene-8β-pyrrolizidine (II),* a (+)-heliotridane derivative with the relative configuration of heliotridine at C7 (absolute configuration 7R, 88). Of two minor alkaloids isolated, one is the 7β-hydroxy-8α diastereoisomer (V) (absolute configuration 7R, 8R). The other minor alkaloid is isomeric with (II) and (V) but does not possess a 1-methylene group. The alkaloid (V) and the enantiomer of the principal alkaloid have been synthesized by reduction of the appropriate 1-chloromethyl-7-hydroxy-1,2-dehydropyrrolizidine with zinc and sulphuric acid. In this reduction some of the 1-methyl-1,2-dehydropyrrolizidine is formed but the 1-methylenepyrrolizidine is the main product.

A non-cyanide method of electropolishing silver

1978 ◽  
Vol 36 (1) ◽  
pp. 146-147
Author(s):  
R. L. Lyles ◽  
S. J. Rothman ◽  
W. Jäger
Keyword(s):  
Electron Microscopy ◽  
Sulphuric Acid ◽  
Methyl Alcohol ◽  
Health Hazards ◽  
Silver Alloy ◽  
High Quality ◽  
Silver Alloys ◽  
Free Sample ◽  
Specimen Quality ◽  
Standard Techniques

Standard techniques of electropolishing silver and silver alloys for electron microscopy in most instances have relied on various CN recipes. These methods have been characteristically unsatisfactory due to difficulties in obtaining large electron transparent areas, reproducible results, adequate solution lifetimes, and contamination free sample surfaces. In addition, there are the inherent health hazards associated with the use of CN solutions. Various attempts to develop noncyanic methods of electropolishing specimens for electron microscopy have not been successful in that the specimen quality problems encountered with the CN solutions have also existed in the previously proposed non-cyanic methods.The technique we describe allows us to jet polish high quality silver and silver alloy microscope specimens with consistant reproducibility and without the use of CN salts.The solution is similar to that suggested by Myschoyaev et al. It consists, in order of mixing, 115ml glacial actic acid (CH3CO2H, specific wt 1.04 g/ml), 43ml sulphuric acid (H2SO4, specific wt. g/ml), 350 ml anhydrous methyl alcohol, and 77 g thiourea (NH2CSNH2).

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