Showing papers by "Marcello Tiecco published in 1983"

Nucleophilic aromatic substitutions of unactivated aryl halides by methyl selenide anions. Synthesis and selective dealkylations of aryl alkyl selenides

Abstract: Synthese de (methyl phenyl)-, (aryl methyl)-, seleniures, de dialkylseleno-1,4- et (alkylseleno-1 alkylthio-4)-benzenes

Nucleophilic substitutions of unactivated vinyl halides with alkanethiolate anions in hexamethylphosphoramide

Abstract: Etude de la reaction du β-bromo styrene avec des alcanethiolates de sodium; obtention des (alkyl styryl) sulfures avec un haut rendement. Avec les di-, tri- et tetra-chloro ethylenes, obtention des derives di-, tri- et tetra-alkylthio correspondants

Homolytic Aromatic Substitution by Alkyl Radicals

Abstract: In the earliest work the reactions of alkyl radicals with aromatic compounds were considered only from the point of view of their theoretical interest. These investigations were, in fact, carried out to correlate theoretical parameters calculated for some representative unsubstituted homoaromatic and heteroaromatic compounds with their reactivity toward simple alkyl radicals such as methyl, trichloromethyl, and trifluoromethyl. Thus, whereas homolytic aromatic arylations were thoroughly investigated, radical alkylations were practically neglected for many years. This stemmed in part from two fundamental difficulties which were encountered in the few cases in which detailed investigations of these reactions were attempted. Convenient and versatile sources of alkyl radicals were not available and, most of all, the alkylation products were obtained in low yields and with low substrate and positional selectivity. The alkyl radicals, as well as the primary intermediates formed by their addition to the aromatics gave, in fact, several side reactions which seriously interfered with the simple aromatic substitution process (1), thus leading to complex reaction mixtures.

Synthesis of aryl thiocyanates from aryl alkyl sulphides. conversion of unactivated aryl halides into aryl thiocyanates

Abstract: Aryl alkyl sulphides, easily obtained from aryl halides, can be selectively dealkylated in HMPA by treatment with sodium, sodium methanethiolate or sodium methoxide. The resulting solutions, containing the sodium arenethiolates, when treated with BrCN or ICN, afford the corresponding aryl thiocyanates in moderate to good yields. A by-product is obtained in several cases to whom the structure of ArSP(O)(NMe2)2 has been attributed.

Convenient Synthesis of Lithium Methyl Selenide An Efficient Reagent for the SN2 Cleavage of Esters

Abstract: The synthesis of alkyl selenides has attracted considerable attention1-3 during the last few years in view of their importance as reagents and intermediates in organic synthesis.4 Several methods have been described for the introduction of selenium into organic molecules starting from elemental selenium.1–3

Selective monoarylation and ‐alkylation of bis(alkylthio)benzenes. the importance of steric effects in the nickel‐catalyzed crosscoupling of aryl alkyl sulfides with grignard reagents

Abstract: Synthetically useful procedures to effect selective conversion of C-S into C-C bonds have been developed by taking advantage of the sensitivity of reactions of Grignard reagents with aryl alkyl sulphides, catalyzed by low-valent nickel species, to steric effects. It is shown that the course of these reactions is influenced by the steric requirements of both the aryl and the alkyl moieties of the sulphides. Thus, selective mono-arylation and alkylation of easily available bis(alkylthio)benzenes can be effected in medium to high yields. This allows the introduction of two different aryl or alkyl groups into the benzene nucleus by sequential substitution of the two alkylthio functions.