Halogen-metal Exchange Reaction Research Articles

Dianion metallation reactions of n,n-dimethylvanillylamine and n,n-dimethylisovanillylamine

The utility of dianion chemistry in the synthesis of polyfunctional aromatics is demonstrated by the direct lithiation of the vanillylamine 1 and by the metal-halogen exchange reaction of the bromo isovanillylamines 9 and 10.

Fluorohalogeno compounds. I. The grignard reaction of some fluorohalogenoethanes

An extension of the scope of the Grignard reaction of fluorinated compounds is reported. Fluorohalogenoethanes of the general formula CF 3CXYZ ( X = F,Cl,Br ; Y,Z = Cl,Br ) were found to undergo smoothly the metal-halogen exchange reaction with alkyl- or aryl-magnesium halides at low temperature to yield organometallic compounds CF 3CXYMgHal. The Grignard compounds were reacted with a series of aldehydes and ketones to give the corresponding alcohols in good to moderate preparative yields.

ChemInform Abstract: REGIOSPECIFIC SYNTHESIS OF AROMATIC COMPOUNDS VIA ORGANOMETALLIC INTERMEDIATES. II. 1,3,5‐(TRIMETHYLMETAL(IV))BENZENE COMPOUNDS

Abstract Sequential metal-halogen exchange reactions between n-C4H9Li and 1,3,5-tribromobenzene and reaction at each step with (CH3)3MIVCl (MIV  Si, Ge, Sn) has provided a 1,3,5-(trimethylmetal(IV))benzene compound. This class of compounds can be synthesized either through a step-wise procedure, where the various intermediates are isolated, or in a continuous metal-halogen exchange process without isolation of various intermediates.

Regiospecific synthesis of aromatic compounds via organometallic intermediates: II. 1,3,5-(Trimethylmetal(IV))benzene compounds

Sequential metal-halogen exchange reactions between n-C 4H 9Li and 1,3,5-tribromobenzene and reaction at each step with (CH 3) 3M IVCl (M IV  Si, Ge, Sn) has provided a 1,3,5-(trimethylmetal(IV))benzene compound. This class of compounds can be synthesized either through a step-wise procedure, where the various intermediates are isolated, or in a continuous metal-halogen exchange process without isolation of various intermediates.

Regiospecific synthesis of aromatic compounds via organometallic intermediates: I. para-substituted benzenes

Para-substituted benzene compounds, p-XC 6H 4X′ (X  CF 3C(O) and X′  CH 3, CO 2H, C(O)CF 3, C(O)CH 3, C(O)H and SH) have been prepared via sequential metal-halogen exchange reactions between p-BrC 6H 4Br and n-C 4H 9Li and the appropriate electrophiles. Low reaction temperature is critical to stabilization of the various intermediates. The CF 3 group has a pronounced effect on providing stability to the lithium hemiketal intermediates.

ChemInform Abstract: THE REACTION OF 2,3,4‐TRICHLOROTHIOPHENE WITH ALKYLLITHIUM REAGENTS

AbstractDas Thiophen (I) reagiert mit 1 Äquiv.

Zur synthese einiger neuer heterocyclisch substituierter stannane

The in 2-position trimethylstannylated heterocycles are formed in good yields by reaction of the lithiated heterocycles benzothiazole, N-methylbenzimidazole, N-methylimidazole, N-methyltriazole, pyridine, chinoline and thiazole with trimethylchlorostannane. The thermolabile lithium compounds are synthesized by metallation or by metal-halogen exchange reactions according to known procedures.

The reaction of 2,3,4-trichlorothiophene with alkyllithium reagents

2,3,4-Trichlorothiophene undergoes metal-hydrogen exchange with one equivalent of butyllithium inTHF at −78°C to give trichloro-2-thienyllithium in 91% yield. No metal-halogen exchange is observed to have taken place. Witht-butyllithium under similar conditions, however, the metalhalogen exchange reaction occurs but only to the extent of 8%; the main reaction remains to be the metal-hydrogen exchange. 2,3,4-Trichlorothiophene reacts with two equivalents of butyllithium in ether at −5°C to give 3,4-dichloro-2,5-dilithiothiophene in 96% yield.

Metallation and metal-halogen exchange reactions of imidazoles

1-Ethoxymethyl-2-phenylthioimidazol-5-yl-lithium (4) has been prepared by metallation of 1-ethoxymethyl-2-phenylthiomidazole with n-butyl-lithium in ether or tetrahydrofuran and allowed to react with carbon dioxide, 4-methylbenzaldehyde, dimethyl disulphide, diphenyl disulphide, and the disulphide prepared from 2-mercaptoacetaldehyde diethyl acetal. 1-Ethoxymethyl-5-methylthio-2-phenylthioimidazol-4-yl-lithium (18) has been prepared via bromination of 1-ethoxymethyl-5-methylthio-2-phenylthioimidazole (9) and exchange of the bromine atom in the product (15) with n-butyl lithium. It has been treated with dimethyl disulphide, NN-dimethylformamide, and carbon dioxide, to give the corresponding sulphide (14), aldehyde (16), and acid (17), respectively. 2,5(4)-Bis(phenylthio)imidazole (23) prepared by treatment of its 1-ethoxymethyl derivative (10) with acid, iodinated in the 4-position to yield 4(5)-iodo-2,5(4)-bis(phenylthio) imidazole (24).

Metallation and metal–halogen exchange reactions of imidazoles

Some reactions (reagents in parentheses) are reported of 1-ethoxymethyl-2-phenylthioimidazol-5-yl-lithium {Me2S2, Ph2S2, [(EtO)2CHCH2]2S2}, 1-ethoxymethyl-5-methylthio-2-phenylthioimidazol-4-yl-lithium (Me2S2, HCONMe2, CO2), 4, 5-dibromo-1-ethoxymethyl-imidazol-2-yl-lithium (Me2S2, Ph2S2), and 2-substituted derivatives of 4-bromo-1-ethoxymethylimidazol-5-yl-lithium (e.g. with Me2S2), prepared by metallation or metal halogen exchange reactions.

Some Selective Metal-Halogen Exchange Reactions of Perchloro(2-phenylthiophene)

Some Selective Metal-Halogen Exchange Reactions of Perchloro(2-phenylthiophene)

ChemInform Abstract: PREPARATION OF (NP(P‐OC6H4LI)2)3 BY METAL‐HALOGEN EXCHANGE, AND ITS REACTIONS WITH ELECTROPHILES

AbstractDie Titelverbindung (IIa) wird durch die Reaktion des p‐ Brom‐Analogen (I) mit n‐Butyl‐Li gebildet.

Preparation of [NP(p-OC6H4Li)2]3 by metal-halogen exchange, and its reactions with electrophiles

Abstract : The first example of a successful metal-halogen exchange reaction between n-butyllithium and a hexa(p-halogenophenoxy)cyclotriphosphazene is described. The hexalithio derivative was allowed to react with electrophiles to yield carboxylic acid, stannane, and phosphine-derivatives. (Author)

Synthese d'oligomeres a sequences perfluorees

The synthesis of block oligomers containing a perfluoroalkyl sequence has been achieved by an anionic technique. For this purpose, a monolithiated oligomer (e.g. oligoisoprenyl or oligostyryl) is deactivated by a perfluoro compound “R 1X”. The optimisation of the coupling over the metalhalogen exchange reaction is studied. 19F NMR analyses of the block oligomers allow identification of the reactive site in the “R 1X” compound.

Polyhalogenoaromatic compounds : XXXV. Metal-halogen exchange between n-butyllithium and polyhalogenobipyridines

Metal—halogen exchange between n-butyllithium and 2,2'-dibromohexachloro-4,4,bipyridine takes place at the 2- and 2'-positions; no rearrangement leading to 3-(5-)lithiobipyridines is observed. In the transition state for the metal—halogen exchange reaction the substrate probably has partial carbanionic character.

The preparation of some reactive 1,6-disubstituted perfluorohexanes

Reactive 1,6-disubstituted perfluorohexanes have been prepared via the reaction of 1,6- bis (dimethylhydrosilyl)-perfluorohexanes with alkyllithium and Grignard reagents. The resulting species may be derivatized in the same manner as organolithium reagents, but are appreciably more stable than the 1,6-dilithioperfluorohexane which is presumably generated by the halogen-metal exchange between an alkyllithium reagent and Br(CF 2) 6Br. 1,6-bis(Bromomagnesium)-perfluorohexane was also prepared in good yield by a halogen-metal exchange reaction.

Some perfluoroalkyl grignard reagents and their derivatives

Some perfluoroalkyl Grignard reagents have been prepared in high yields through halogen-metal exchange reactions between perfluoroalkyl iodides (RfI) and EtMgBr. Derivatization with Me3SiCl gave satisfactory yields of the corresponding silylated products in THF. However, ether was a very poor solvent for reaction of RfMgBr with these chlorosilanes. The exchange reaction between RfI and EtMgBr was nearly quantitative in ether as evidenced by high yields of the 1-hydroperfluoroalkanes upon hydrolysis, but the major production from the attempted silylation in ether was a trans- vinyl bromide [1], i. e. Spectral data are presented for several new compounds.

Reactions of Methylcalcium Iodide. II. Carboxylation, Metalation, and Metal-Halogen Exchange Reactions

Abstract Utility of methylcalcium iodide in several organic reactions in tetrahydrofuran was shown. Carboxylation of methylcalcium iodide at −70 °C gave acetic acid in 57–63% yield. Metallation of indene and fluorene by methylcalcium iodide at −30 °C gave 3-indenyl- and 9-fluorenylcalcium iodides in 99 and 93% yields, respectively. Metal-halogen exchange reactions of methylcalcium iodide with halobenzenes were rather slow.

Polyhalogenoaromatic compounds : XXX. The metalhalogen exchange reaction between n-butyllithium and 2,3,4,5,6-pentachloro- N, N-dimethyl- benzylamine

The reaction of n-butyllithium with 2,3,4,5,6-pentachloro- N, N-dimethyl- benzylamine proceeds by metalhalogen exchange at the positions meta and para to the dimethylaminomethyl group, but not at the ortho position. Coordination by the substituent thus plays little or no part in determining which position undergoes reaction.

Synthesis and reactions of perfluoro-n-octylmagnesium bromide

Perfluoro-n-octylmagnesium bromide has been conveniently synthesized through the metal-halogen exchange reaction between perfluoro-n-octyl iodide and ethyl- or phenyl-magnesium bromide. The thermal stability of the Grignard reagent and the products of the thermal decomposition have been estimated in diethyl ether and tetrahydrofuran. Reactions of the Grignard reagent with various substrates such as water, acetone, hexafluoroacetone, trimethylchlorosilane and carbon dioxide indicate the synthetic utility of n-octylmagnesium bromide.