Halogen-metal Exchange Reaction Research Articles

Synthesis of perfluoroaliphatic grignard reagents

Perfluoraliphatic mono- and di-Grignard reagents (R fMgX, XMgR′ fMgX) have been conveniently synthesized in excellent yields (90–100%) through metalhalogen exchange reactions. The degree of exchange has been found to be subject to a number of experimental parameters, e.g. the nature of the solvent (tetrahydrofuran vis-à-vis diethyl ether), the type of halide displaced, the organomagnesium exchange reagent and the stoichiometry. These organomagnesium reagents have sufficient thermal stability at low temperatures (−70°) to be useful as intermediates for the synthesis of a variety of compounds. Various perfluoroaliphatic Grignard reagents have been reacted with H 3O +, CO 2, (CF 3) 2CO and cyclohexanone to yield R fH, R fCO 2H, R f(CF 3) 2OH and 1-cyclo-C 6H 10(OH)R f compounds, respectively. The selection of the proper reaction conditions, i.e. solvent, temperature and reaction time, has been found to be extremely important in the preparation of derivatives of the various perfluoroaliphatic Grignard reagents.

Syntheses employing pyridyllithium reagents: new routes to 2,6-disubstituted pyridines and 6,6′-disubstituted 2,2′-bipyridyls

New 2,6-disubstituted pyridine derivatives have been synthesized employing 6-bromo-2-lithiopyridine as an intermediate. Subsequent replacement of the 6-bromine can be effected by metal-halogen exchange or other reactions in some cases. Reactions of the previously unreported 6-lithio-2,2′-bipyridyl and 6,6′-dilithio-2,2′-bipyridyl are described. Cupric chloride was found to be an effective coupling agents for lithiopyridine reagents, allowing facile and high yield syntheses of substituted 2,2′-bipyridyls.

The preparation and reactions of some dimetallic compounds derived from tetrachlorothiophene

The use of tetrachlorothiophene in the preparation of several dimetallic derivatives is described. Thus, 2,5-dilithiodichlorothiophene was prepared in nearly quantitative yield via a halogen-metal exchange reaction between n-butyllithium and tetrachlorothiophene. This dilithio compound was converted, also in satisfactory yield, to a dicopper derivative by reaction with CuCl or Cul in a mixture of tetrahydrofuran and ether at low temperature. Some derivatives of each of the dimetallic compounds were prepared, and among characterizations were those of IR, NMR, and mass spectrometry.

Polyhalogenoaromatic compounds. Part XIX. Metal–halogen exchange reactions of n-butyl-lithium with tetrabromo-4-pyridyl and tetrachloro-2-pyridyl derivatives

The reaction of n-butyl-lithium with tetrabromo-4-methoxypyridine, tetrabromo-4-dimethylaminopyridine, and tetrabromo-4-piperidinopyridine led to the corresponding tribromo-3-pyridyl-lithium derivatives. When heated in the presence of furan, tribromo-4-methoxy-3-pyridyl-lithium gave an adduct of 5,6-dibromo-4-methoxy-2-pyridine. The reaction of n-butyl-lithium with tetrachloro-6-methoxypyridine, tetrachloro-6-dimethylamino-pyridine, tetrachloro-6-pyrrolidinopyridine and tetrachloro-6-piperidinopyridine led to the corresponding trichloro-4-pyridyl-lithium derivatives. When heated in the presence of furan, each of these lithium compounds gave only one of the two possible pyridyne adducts; evidence is presented that the 2-substituted 3-pyridyne was involved in each case. Factors governing the position of metal–halogen exchange in polyhalogeno-benzenes and -pyridines are discussed.

Halogen–Metal Exchange Reactions with 2-Halogenoalkylsilicon Compounds

2-Bromoethyltriphenylsilane undergoes extensive halogen–metal exchange with phenylmagnesium bromide in tetrahydrofuran, giving ethyltriphenylsilane and 1,4-bis(triphenylsilyl)butane as principal products. In diethyl ether the exchange reaction is suppressed and the main product is 2-phenylethyltriphenylsilane. With propylmagnesium bromide and ethylmagnesium bromide halogen–metal exchange occurs even in diethyl ether. It was concluded that some additional stability, not available to alkyl carbanions. was possessed by the carbanion Ph3Si·CH2·CH2−.

The halogen-metal exchange reaction between perfluoro-n-heptyl iodide and n-butyllithium

Perfluoro-n-heptyl iodide and 1–1.5 molar equivalents of n-butyllithium in diethyl ether or halide-free diethyl ether/pentane undergo 40–50% halogen-metal exchange below −90° and form a stable heterogeneous system. The stability of the perfluoro-n-heptyllithium present is attributed to its association with perfluoro-n-heptyl iodide. Such a mixture reacts only slowly with acetaldehyde below −90° to give a low yield of 1-(perfluoro-n-heptyl)ethanol. Halogen-metal exchange is complete in the presence of a sufficient excess of the fluoroalkyliodide, in accord with the relative carbanion stabilities. In the presence of a large excess of n-butyllithium the system is considerably less stable and trans-1-n-butyltridecafluoro-1-heptene is a major product. The stable heterogeneous mixture becomes homogeneous above ca −90°, and in the presence of acetaldehyde the fluoroalkyllithium then undergoes a fast reaction to give a quantitative yield of the fluoroalcohol. Perfluoro-n-heptyllithium decomposes very rapidly even at −75°, but it can be utilised at this and higher temperatures by producing it in the presence of an appropriate substrate. Perfluoro-n-propyl iodide and perfluoroisopropyl iodide also undergo 40–50% halogen-metal exchange when treated with an excess of n-butyllithium in ether below ca. −90°, indicating that the ability of perfluoroalkyllithiums to form stable heterogeneous systems is general. Carboxylation of perfluoro-n-propyllithium, perfluoroisopropyllithium, and perfluoro-n-heptyllithium was effected.

Chemically induced dynamic nuclear polarization evidence for one-electron transfers during some halogen-metal exchange reactions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemically induced dynamic nuclear polarization evidence for one-electron transfers during some halogen-metal exchange reactionsHarold Roy Ward, Ronald G. Lawler, and Robert A. CooperCite this: J. Am. Chem. Soc. 1969, 91, 3, 746–748Publication Date (Print):January 1, 1969Publication History Published online1 May 2002Published inissue 1 January 1969https://doi.org/10.1021/ja01031a041RIGHTS & PERMISSIONSArticle Views111Altmetric-Citations55LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (331 KB) Get e-Alerts Get e-Alerts

On the Halogen-Metal Exchange Reaction between 2-Bromo-3-iodothiophene and Ethyllithium.

On the Halogen-Metal Exchange Reaction between 2-Bromo-3-iodothiophene and Ethyllithium.

Pentachlorophenyl derivatives of silicon and tin

The preparations of some pentachlorophenyl derivatives of silicon and tin by the interaction of pentachlorophenylmagnesium chloride with various chlorosilanes and chlorostannanes were described. It was found that a halogen-metal exchange reaction was operating as well as the coupling reaction. The ultraviolet properties of these derivatives were studied and it was found that each of these pentachlorophenyl derivatives possessed an absorption band at about 200 mη with unusually high molar absorptivity. It was also observed that the molar absorptivities of these compounds increased as the number of pentachlorophenyl groups in the compounds increased. In general, the tin derivatives had higher molar absorptivities than those of the corresponding silicon derivatives.