Search results for "Phosphonium salt"

A Voltammetric Analysis of the Electrochemical Behaviour of Onium Salts at a Mercury Electrode

1980

An analysis of the cyclic voltammograms of the reduction of various onium salt at mercury, produced more detailed information concerning the nature of the reaction pathway, in terms of adsorption, amalgam formation and kinetics of electron transfer, and lead to an interpretation of the characteristic “inverted peak”. An “auto-catalytic” reaction mechanism was indicated, and in conjunction with the preparative experiments [1, 2] a full reduction scheme proposed for the sulphonium salt ([Ph2S+ CH3)]CIO−4) and the phosphonium salt ([Ph2P+ (CH3)2]Br−). Die Analyse der Cyclovoltammogramme der reduktiven Spaltung einiger Phosphonium- und Sulfoniumsaize unterrichtet uber die an der Quecksilberkath…

A facile microsynthesis of 14C-labelled picene

1984

Microscale Wittig olefination of commercially available [7-14C]-benzal dehyde of high specific radioactivity with aryl bromomethyl phosphonium salt and subsequent oxidative photocyclisation affords pure 14C-labelled picene in efficient yield.

NMR enantiodifferentiation of triphenylphosphonium salts by chiral hexacoordinated phosphate anions

2003

BINPHAT anion—rather than TRISPHAT—is an efficient NMR chiral shift reagent for triphenylphosphonium salts containing stereogenic centers on the aliphatic side-chain. BINPHAT—rather than TRISPHAT—anion is an efficient NMR (1H and 31P) chiral shift reagent for chiral triphenylphosphonium salts.

Efficient Synthesis of β-Halogeno Protected L-Alanines and Their β-Phosphonium Derivatives.

2003

Abstract Ring opening of oxazolines, prepared from l -serinates, with trimethylsilyl halides (TMSX) led to β-halogeno-N-benzoyl-α-amino esters in good to excellent yields. Quaternization of triphenylphosphine by the β-bromo or -iodo amino esters gave the corresponding β-phosphonium salts in overall yields of up to 93% and with e.e. >96%. Hydrolysis of the ester function afforded the phosphonium salt bearing an N-benzoyl-α-amino acid substituent, with partial racemization. However, the reaction of the TMSX with the carboxylic salt, prepared by saponification of the starting oxazoline ester, furnished the corresponding β-halogeno-N-benzoyl-α-amino acids in 70–95% yields. Quaternization of tri…

Phosphonium Salt Formation of the Second Kind

1964

Synthesis and Biological Evaluation of Combretastatin A-4 and Three Combretastatin-Based Hybrids

2012

The syntheses of combretastatin A-4 from gallic acid and of three combretastatin-based hybrids are described. Starting from commercial gallic acid, the phosphonium salt (3,4,5-trimethoxybenzylphosphonium bromide) is synthesized and coupled, through a Wittig reaction, with several aldehydes, including methoxymethyl-protected isovanillin, the aldehyde γ-bicyclohomofarnesal having a labdane skeleton, 3-(3-pyridyl) propanal, and furfural. The biological properties of the cis-coupled compounds as cytotoxic, antiviral and antifungal agents are also reported. In addition, pyrogallol, gallic and 3,4,5-trimethoxybenzoic acids have been studied biologically.

Stereoselective synthesis of unsaturated and functionalized L-NHBoc amino acids, using Wittig reaction under mild phase-transfer conditions.

2012

The stereoselective synthesis of a new amino acid phosphonium salt was described by quaternization of melting triphenylphosphine with the γ-iodo NHBoc-amino ester, derived from L-aspartic acid. The deprotection of the carboxylic acid function to afford the phosphonium salt with a free carboxylic acid group was achieved by a palladium-catalyzed desallylation reaction. This phosphonium salt was used in the Wittig reaction with aromatic or aliphatic aldehydes and trifluoroacetophenone, under solid-liquid phase-transfer conditions in chlorobenzene and in the presence of K(3)PO(4) as weak base, to afford the corresponding unsaturated amino acids without racemization. Thus, the reaction with subs…

Studien zum Vorgang der Wasserstoffübertragung 46. Zur kathodischen Spaltung von Alkyl- und Cycloalkyl(triphenyl)-phosphoniumsalzen; Abhängigkeit der…

1977

Die kathodische Spaltung von Methyl-, Butyl- und einiger Cycloalkyl(triphenyl)phosphoniumsalze wurde potentiostatisch und galvanostatisch durchgefuhrt. Beim Methyl(triphenyl)-phosphoniumsalz hangt die prozentuale Zusammensetzung der Spaltprodukte: Triphenylphosphin und Methyl(diphenyl)phosphin sowohl vom Potential als auch von der Temperatur ab, die sich ihrerseits wieder gegenseitig beeinflussen. Zusatze unterschiedlich strukturierter quartarer Ammoniumsalze als Leitsalz verandern das prozentuale Verhaltnis (C6H5)3P/(C6H5)2PCH3 nicht, wohl aber der Zusatz von Essigsaure, welche die Bildung von Methyl(diphenyl)phosphin begunstigt. - Bei den Cycloalkyl(triphenyl)phosphoniumsalzen mit Cyclohe…

Synthèse de pinces à fluorures dérivées d'aminoacides pour l'imagerie TEP

2014

This thesis project, which is part of a collaboration between the Institut de Chimie Moléculaire de l’Université de Bourgogne and the Positron Emission Tomography Research Centre, is about the synthesis of fluoride pincers derived from amino acids based on 18F-B bond construction to get a new class of PET imaging agents. First, this project concerned the design, synthesis and characterisation of new boronato and trifluoroborato phosphonium amino acid salts. Quaternisation of o-boronate phenyl phosphine with β-iodo amino esters or γ-iodo amino ester leads to the corresponding salts without racemisation and in yields up to 88%. Saponification of boronato phosphonium amino esters afford the fr…

Phosphororganische Verbindungen, 85. Kinetische Untersuchungen der Umsetzung organischer Phosphorverbindungen mit Nucleophilen und Supernucleophilen

1977

Bei der alkalischen Spaltung von quartaren Phosphoniumsalzen und tertiaren Phosphinoxiden zeigt HOO⊖ keinen α-Effekt. Die Spaltung der P–C-Bindung wird auch nicht durch Gruppen erleichtert, welche uber die Ausbildung von H-Brucken den Angriff von HOO⊖ am Phosphoniumzentrum fordern. — In Ubereinstimmung mit den Ergebnissen anderer Autoren wird bei der Hydrolyse der Phosphin-, Phosphon- und Phosphorsaureester 1, 2 und 3 in Gegenwart von H2O2 ein α-Effekt beobachtet, der sich in einer Hydrolysebeschleunigung um einen Faktor von ca. 100 ausdruckt. Die Hydrolysegeschwindigkeit nimmt sowohl mit HO⊖ als auch mit HOO⊖ entsprechend folgender Reihenfolge ab: Diphenylphosphinsaure-(p-nitrophenyl)ester…