Reductive cleavage of 2-alkoxy- and 2-aryloxy-tetrahydropyrans with LiAlH4–AlCl3

1967 ◽  
Vol 45 (21) ◽  
pp. 2547-2558 ◽  
Author(s):  
U. E. Diner ◽  
R. K. Brown
Keyword(s):  
Ring Cleavage ◽  
Side Chain ◽  
Resonance Spectroscopy ◽  
Trans Isomers ◽  
Aryl Group ◽  
Side Chain Cleavage ◽  
Chain Cleavage ◽  
Cis And Trans Isomers ◽  
Steric Factors ◽  
Cis And Trans

A series of 2-alkoxy- and 2-aryloxy-tetrahydropyrans has been hydrogenolyzed in ether by LiAlH4–AlCl3. As the alkyl group attached to the exo oxygen atom is changed from primary to tertiary, the proportion of ring cleavage to side-chain cleavage increases. Only side-chain cleavage occurs with the 2-aryloxytetrahydropyrans. The results are explained in terms of the polar properties of the alkyl or aryl group attached to the ring oxygen or the side-chain oxygen. Any control by steric factors is considered to be submerged by the polar effects, but does have a clearly apparent directive effect when the polar factors are equal for the two routes of cleavage. The results of the hydrogenolysis of 6-substituted 2-alkoxytetrahydropyrans could be explained on the same basis.The configurations of the cis and trans isomers of the disubstituted tetrahydropyrans were determined by nuclear magnetic resonance spectroscopy. Their conformational preference is discussed.

scholarly journals Photolysis of carboxymethylflavin in aqueous and organic solvent: a kinetic study

RSC Advances ◽  
2019 ◽  
Vol 9 (46) ◽  
pp. 26559-26571 ◽  
Author(s):  
Iqbal Ahmad ◽  
Tania Mirza ◽  
Syed Ghulam Musharraf ◽  
Zubair Anwar ◽  
Muhammad Ali Sheraz ◽  
...  
Keyword(s):  
Acid Solution ◽  
Organic Solvent ◽  
Kinetic Study ◽  
Alkaline Solution ◽  
Ring Cleavage ◽  
Side Chain ◽  
Keto Acid ◽  
Side Chain Cleavage ◽  
Chain Cleavage

Carboxymethylflavin (CMF) undergoes photolysis in acid solution to form lumichrome (LC) and in alkaline solution, LC and lumiflavin (LF) by side-chain cleavage and β-keto acid and a dioxoquinoxalaine (DQ) compound by isoalloxazine ring cleavage.

Five-coordinate iron(II) porphyrins derived from meso-α,β,γ,δ tetraphenylporphin: synthesis, characterization, and coordinating properties

1979 ◽  
Vol 57 (14) ◽  
pp. 1804-1813 ◽  
Author(s):  
Michel Momenteau ◽  
Bernard Loock ◽  
Emile Bisagni ◽  
Michel Rougee
Keyword(s):  
Metal Ion ◽  
Side Chain ◽  
Intramolecular Coordination ◽  
Trans Isomers ◽  
Visible Spectroscopy ◽  
Cis And Trans Isomers ◽  
The Stability ◽  
Heterogeneous Reduction ◽  
Cis And Trans ◽  
Reduced Forms

Meso-α,β,γ,δ, tetraphenylporphin derivatives bearing acrylic (cis and trans isomers) and propionic side chains with a terminal imidazole group have been synthesized. Intermediate compounds obtained during their preparation were characterized by visible spectroscopy and nmr. In non-coordinating solvents (benzene or toluene), the iron(III) complexes of these compounds do not show intramolecular coordination of the terminal base on the metal ion. The reduced forms of the compounds have been obtained from ferric forms by heterogeneous reduction with aqueous dithionite and exhibit optical spectra characteristic of five-coordinate ferrous complexes. The nitrogenous bases and carbon monoxide affinities of the latter have been measured and the results indicate that the 'transinfluence' exerted by the terminal imidazole does not depend greatly on the nature and the structure of the covalent side chain. In contrast the stability of the five-coordinate compounds depends on the side chain (trans acrylic < propionic < cis acrylic) as suggested by the values reported for the replacement constants of the terminal imidazole by 4-cyanopyridine in unsymmetrical six-coordinate derivatives. The stability of these compounds towards oxidation is also reported.

Adduct Intermediates in the Side-chain Nitration of 1,4-Dimethylnaphthalene

1972 ◽  
Vol 50 (24) ◽  
pp. 3988-3992 ◽  
Author(s):  
Alfred Fischer ◽  
Alan Leslie Wilkinson
Keyword(s):  
Acetic Acid ◽  
Nitric Acid ◽  
Acetic Anhydride ◽  
Room Temperature ◽  
Methylene Chloride ◽  
Side Chain ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Naphthyl Acetate

cis and trans isomers of 1,4-dimethyl-4-nitro-1,4-dihydro-1-naphthyl acetate (1) have been isolated from a mixture of 1,4-dimethylnaphthalene and nitric acid in acetic anhydride by quenching at −40°. At room temperature only 1-methyl-4-nitromethylnaphthalene (4) is obtained. The conversion of 1,4-dimethylnaphthalene to 4 and of the cis (1a) and trans (1b) adducts to 4, by nitric acid in acetic anhydride, has been followed by n.m.r. 1,4-Dimethyl-4-nitro-1,4-dihydro-1-naphthyl nitrate (5) appears to be the immediate product from nitration of 1,4-dimethylnaphthalene in acetic anhydride, methylene chloride, or nitromethane. In acetic anhydride 5 is converted into 1. Decomposition of 1 in acetic acid gives 1,4-dimethyl-2-naphthyl acetate and some 4. The formation of 4 in this reaction is suppressed by urea.

Conformations, configurations, and proton reactions of colbalt(III) complexes

1967 ◽  
Vol 20 (2) ◽  
pp. 257 ◽  
Author(s):  
DA Buckingham ◽  
L Durham ◽  
AM Sargeson
Keyword(s):  
Amino Acid ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Proton Exchange ◽  
Resonance Spectroscopy ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans

Proton magnetic resonance spectroscopy allows the cis and trans isomers of [CoX2 en2] complexes to be distinguished. Some information has been obtained concerning the rate of chelate conformational interchange for cobalt-ethylenediamine, propylenediamine, N-methylethylenediamine, and malonate rings. For [Co(amino acid)en2]2+ complexes the diastereoisomeric pairs can be differentiated and the relative rates of CH and NH proton exchange have been observed for a variety of chelate rings including cobalt-amino acid, acetylacetonato, ethylenediamine, and malonato.

The Effect of N-Substitution on the Rates of Saponification of Some Amino Acid Esters

1971 ◽  
Vol 49 (21) ◽  
pp. 3468-3476 ◽  
Author(s):  
Jocelyn E. Purdie ◽  
N. Leo Benoiton
Keyword(s):  
Amino Acid ◽  
Methyl Esters ◽  
Activation Parameters ◽  
Side Chain ◽  
Amino Acid Esters ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Hydrolysis Of ◽  
Acid Esters

The saponification rates (measured at 25 ° by a titrimetric method) of the unprotonated forms of the methyl esters of glycine, alanine, leucine, valine, and phenylalanine were compared with those of the N-methyl, the N-acetyl, and the N-acetyl, N-methylamino acid analogues. N-Acetylation slightly increased or decreased the rate but N-methylation caused a reduction by as much as a factor of ten, depending on the complexity of the side-chain. The esters of the N-acetyl, N-methylamino acids, which exist as cis and trans isomers, were saponified at rates intermediate between those of the esters of the N-acetylamino acids and N-methylamino acids. Activation parameters were obtained for the phenylalanine and leucine derivatives. N-Methylation resulted in an increase in ΔH≠ and ΔS≠ which was attributed in part to solvation effects. The hydrolysis of the cationic esters of glycine and alanine was still evident at pH 11.0. N-Methylation had little effect on the rates of saponification of the charged forms.

Formation of Adducts in the Nitration of p-Xylene. Exchange and Rearomatization Reactions of p-Xylene Adducts

1974 ◽  
Vol 52 (23) ◽  
pp. 3960-3970 ◽  
Author(s):  
Alfred Fischer ◽  
John Neilson Ramsay
Keyword(s):  
Acetic Anhydride ◽  
Sodium Methoxide ◽  
Major Product ◽  
Side Chain ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Acid Catalyzed ◽  
Cis And Trans

Nitration of p-xylene in acetic anhydride gives as the major product cis and trans isomers of the adduct 1,4-dimethyl-4-nitro-1,4-dihydrophenyl acetate (1) as well as 2-nitro-p-xylene. The acetoxynitro adducts 1a and 1b are stereospecifically cleaved to the hydroxynitro adducts 2a and 2b, respectively, by sodium methoxide. Acid-catalyzed exchange of OAc in 1 for OCH3, OCHO, OCH2C6H4CH3-p occurs and is nonstereospecific. Rearomatization of 1 gives 2-nitro-p-xylene, side-chain (benzylic) derivatives, and 2,5-xylyl acetate. The relevance of these reactions to side-chain substitution of arenes under electrophilic conditions is discussed.

P450 side-chain cleavage enzyme autoantibodies in canine Addison's disease

2013 ◽  
pp. 1-1
Author(s):  
Alisdair Boag ◽  
Kerry McLaughlin ◽  
Mike Christie ◽  
Peter Graham ◽  
Harriet Syme ◽  
...  
Keyword(s):  
Addison’S Disease ◽  
Side Chain ◽  
Addison's Disease ◽  
Side Chain Cleavage ◽  
Chain Cleavage ◽  
Cleavage Enzyme
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