The competitive scissions of cycloalkane oxiranes by charged and neutral nucleophiles in acidic aqueous methanol

1977 ◽  
Vol 55 (23) ◽  
pp. 4144-4155 ◽  
Author(s):  
John W. Bovenkamp ◽  
Robert Y. Moir ◽  
Robert A. B. Bannard
Keyword(s):  
Perchloric Acid ◽  
Acidic Solution ◽  
Chloride Ion ◽  
Trans Isomers ◽  
Aqueous Methanol ◽  
Product Analysis ◽  
Cis And Trans Isomers ◽  
Acid Catalyzed ◽  
Cis And Trans

Six related oxiranes (the cis and trans isomers derived from 3-methoxycyclopentene and from 3-methoxycyclohexene, as well as the oxiranes from the corresponding unsubstituted olefins) were each treated under the same conditions with an acidic solution containing charged and uncharged nucleophiles (chloride ion, water, and methanol). The corresponding perchloric acid catalyzed scissions were also carried out. Accurate and reproducible methods of product analysis for the reaction mixtures were developed. In this way, nucleophilic attacks upon different oxiranes were compared directly. Attacks by different nucleophiles upon the same oxirane, or by a single nucleophile upon different positions of the same oxirane, were compared in the very same solution. The results are considered to provide the most extensive demonstration of the effects of charge orientation yet available. The synthesis of some new isomeric 1,2,3-trisubstituted diols and dimethoxyalcohols are reported.

Some reactions of 2,4-dimethoxytetrahydropyrans

1969 ◽  
Vol 47 (17) ◽  
pp. 3099-3106 ◽  
Author(s):  
M. J. Baldwin ◽  
R. K. Brown
Keyword(s):  
Room Temperature ◽  
Equilibrium Mixture ◽  
Anomeric Effect ◽  
Temperature Reaction ◽  
Trans Isomers ◽  
Kcal Mole ◽  
A Value ◽  
Cis And Trans Isomers ◽  
Acid Catalyzed ◽  
Cis And Trans

Acid-catalyzed elimination of methanol from 2,4-dimethoxytetrahydropyran (1) produces 2-methoxy-5,6-dihydro-2H-pyran (3) rather than the expected olefin 4-methoxy-3,4-dihydro-2H-pyran (2).The reaction of 1,3-dibromo-5,5-dimethylhydantoin with 3 in ether – methanol gives a 2:1 mixture of the isomers 3β-bromo-2α,4α-dimethoxytetrahydropyran (5a) and 3α-bromo-2α,4β-dimethoxytetrahydropyran (5b) respectively. A rationale is given to explain the preponderance of 5a over 5b and the highly selective attack of the bromine of the hydantoin and the methanol on C-3 and C-4 respectively of the double bond of 3. Reduction of 5ab with zinc in ethanol provides only compound 3.The room temperature reaction of 1 in a mixture of water and 1,2-dimethoxyethane containing Amberlite IR-120, produces 2-hydroxy-4-methoxytetrahydropyran (6) as an equilibrium mixture of cis and trans isomers in the ratio 1:1. This gave a value of 0.9 kcal/mole for the anomeric effect in 6. Pyrolysis of the derivative, 2-acetoxy-4-methoxytetrahydropyran failed to produce the olefin 2 and resulted only in extensive decomposition.

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.

scholarly journals Identification of Anthocyanin Compounds in Butterfly Pea Flowers (Clitoria ternatea L.) by Ultra Performance Liquid Chromatography/Ultraviolet Coupled to Mass Spectrometry

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4539
Author(s):  
Nguyen Minh Thuy ◽  
Vo Minh ◽  
Tran Ben ◽  
My Tuyen Thi Nguyen ◽  
Ho Ha ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Ultra Performance Liquid Chromatography ◽  
Negative Ion ◽  
Trans Isomers ◽  
Clitoria Ternatea ◽  
Flower Extract ◽  
Cis And Trans Isomers ◽  
Butterfly Pea ◽  
Cis And Trans

Butterfly pea flower have great sensory attraction, but they have not yet been used widely in Vietnam. Extracts of butterfly pea flowers can be used conveniently as a natural blue colorant for food products. In this study, the identification of anthocyanin compounds in butterfly pea flowers was performed by UPLC coupled with a UV and Mass spectrometer instrument. Positive and negative ion electrospray MS/MS chromatograms and spectra of the anthocyanin compounds were determined. By analyzing the chromatograms and spectra for each ion, five anthocyanins were identified in the butterfly pea flower extract; these were delphinidin-3-(6”‐p-coumaroyl)-rutinoside, cyanidin 3-(6”-p-coumaroyl)-rutinoside, delphinidin-3-(p-coumaroyl) glucose in both cis- and trans- isomers, cyanidin-3-(p-coumaroyl-glucoside) and delphinidin-3-pyranoside. Additionally, based on their intensity, it was determined that cyanidin-3-(p-coumaroyl-glucoside) was the most abundant anthocyanin, followed by cyanidin 3-(6”-p-coumaroyl)-rutinoside, delphinidin-3-(p-coumaroyl-glucoside), delphinidin-3-(6”-p-coumaroyl)-rutinoside and delphinidin-3-pyranoside. In this study, cyanidin derivatives were discovered in butterfly pea flower extract, where these compounds had not been detected in previous studies.

Unveiling the coexistence of cis- and trans-isomers in the hydrolysis of ZrO2: A coupled DFT and high-resolution photoelectron spectroscopy study

2020 ◽  
Vol 153 (24) ◽  
pp. 244308
Author(s):  
Ali Abou Taka ◽  
Mark C. Babin ◽  
Xianghai Sheng ◽  
Jessalyn A. DeVine ◽  
Daniel M. Neumark ◽  
...  
Keyword(s):  
High Resolution ◽  
Photoelectron Spectroscopy ◽  
Spectroscopy Study ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Hydrolysis Of

PREPARATION OF ERUCIC AND NERVONIC ACIDS LABELLED WITH CARBON-14

1957 ◽  
Vol 35 (8) ◽  
pp. 757-760 ◽  
Author(s):  
K. K. Carroll
Keyword(s):  
Enoic Acid ◽  
Nervonic Acid ◽  
Malonic Ester ◽  
Ester Synthesis ◽  
Trans Isomers ◽  
Carbon 14 ◽  
Cis And Trans Isomers ◽  
Cis And Trans

The malonic ester synthesis of nervonic acid (tetracos-15-enoic acid) has been modified so that the product consists of pure cis rather than a mixture of cis and trans isomers. The modified synthesis has been used for the preparation of C14-labelled erucic and nervonic acids.

Synthesis of cis and trans Isomers of D-Ring Linked Bis-Steroid Pyrazines from 16α-Bromo-17-oxosteroids

2002 ◽  
Vol 67 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Zenon Łotowski ◽  
Jacek W. Morzycki ◽  
Izabella S. Niewczas ◽  
Marta Zdanowicz
Keyword(s):  
Gaseous Ammonia ◽  
Analogous Reaction ◽  
Air Oxidation ◽  
Trans Isomers ◽  
Hydrolysis Products ◽  
Cis And Trans Isomers ◽  
Cis And Trans

Treatment of 16α-bromo-17-oxosteroids 1 and 2 with gaseous ammonia and successive air-oxidation afforded the cis and trans isomers of D-linked bis-steroid pyrazines. Analogous reaction of 1α-bromo-4-nor-5α-cholestan-2-one (3) led to unexpected hydrolysis products.

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