Metalation as a Side Reaction in the Preparation of Organolithium Compounds

Gilman, Henry; Langham, W.H.; Jacoby, Arthur L.

doi:10.1021/ja01870a036

Cited by 128 publications

(72 citation statements)

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“…For instance, UV/visible studies of PAMS, Li in THF even at -78ºC, have not shown any termination even after several hours. However, the termination via other pathways involving side reactions of the carbanion with DBX is possible, for instance via lithium halogen exchange [25]. The resulting halogenated chain ends would be subject to elimination as well as the desired substitution reactions (Scheme 1).…”

Section: Tab 1 Values Andmentioning

confidence: 99%

Synthesis and characterization of macrocyclic poly(.-methylstyrene)

Dong

Hogen‐Esch

2001

E-Polymers

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The synthesis is described of macrocyclic poly( -methylstyrene) (PAMS) by the lithium naphthalide initiated polymerization of AMS followed by high dilution end to end coupling with 1,4-bis(bromomethyl)benzene (DBX). The cyclization is carried out by simultaneous addition of tetrahydrofuran solutions of the PAMS dianion and DBX at about -100ºC. A sample of the matching linear PAMS is obtained by protonation of the PAMS dianion. The purified cycles are obtained by fractional precipitation that is monitored by size exclusion chromatograhy. A careful study of the coupling reactions carried out at high concentrations indicates that coupling is efficient and this is borne out by the ratios () of apparent molecular weights (MW's) of cycles and matching linear polymers. The values of the cycles tend to vary with MW in the same manner as was demonstrated for polystyrene and other vinyl polymers and increase from around 0.74 at MW of about 30000 to values of around 0.82 at MW of about 2500. A higher apparent value was observed for a very low MW PAMS but this sample could not be purified and analyzed adequately. As was also observed for other macrocyclic vinylpolymers, the glass transition temperatures of the cycles are MW independent above MW of about 5000 but decrease sharply at lower MW's.

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Section: Tab 1 Values Andmentioning

confidence: 99%

Synthesis and characterization of macrocyclic poly(.-methylstyrene)

Dong

Hogen‐Esch

2001

E-Polymers

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“…Seit den bahnbrechenden Arbeiten von Gilman, [55] Wittig [56] und Snieckus [57] wurde die dirigierte ortho-Metallierung (DoM) weitreichend zur regioselektiven Funktionalisierung von substituierten Arenen und Heteroarenen verwendet. Zahlreiche Substituenten, beispielsweise Carbamat-, Amid-, Methoxy-oder Cyangruppen, dirigieren die Metallierung durch starke Lithiumbasen bei diesen Reaktionen.…”

Section: Lithiierung Mit Lithiumamidenunclassified

Regio‐ und chemoselektive Metallierung von Arenen und Heteroarenen mit gehinderten Metallamidbasen

et al. 2011

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Die Synthese hoch funktionalisierter Organometallverbindungen gelingt durch C‐H‐Aktivierung zahlreicher ungesättigter Substrate mit Lithiumchlorid‐solubilisierten 2,2,6,6‐Tetramethylpiperidyl‐Basen (TMPnMXm⋅p LiCl). Diese Reagentien erweisen sich als exzellent zur Umwandlung vielfältiger aromatischer sowie heterocyclischer Substrate in nützliche metallorganische Reagentien mit weiter Anwendungsbreite in der organischen Synthese.

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“…114c,d In a paper received by the Journal of the American Chemical Society in October 1938, three months after Wittig's paper had been received by the Berichte, Gilman et al reported their independent discovery of the reaction of o-bromoanisole with n-butyllithium, which gave o-anisyllithium, in agreement with Wittig's finding, and n-butyl bromide. 115 Wittig and Gilman recognized the importance in terms of its potential utility of the lithium-halogen exchange reaction and, to avoid duplication of effort and any disputes, made a gentleman's agreement that Wittig would restrict his continuing investigations to such reactions of aryllithium reagents and that Gilman would carry out his studies with alkyllithiums (ref 114a, footnote 3, p 1198). Gilman had the better of the deal in the long run, for n-butyllithium, and also tert-butyllithium, turned out to be more versatile than phenyllithium and hence became the reagents of choice for use in the lithium-halogen exchange preparation of a great number of organolithium reagents.…”

Section: B Synthesis Of Organolithium Reagents By the Lithiumhalogenmentioning

confidence: 99%