1-Alkylmagnesium bromides

It is also possible to produce covalently bonded alkyl MLs on Si(l 11) surfaces using a variety of chemical reactions with passivated H-terminated Si(l 11), but the preparation methods are more complex than the immersion strategy in part due to the higher reactivity of silicon. This is a major achievement because it allows direct coupling between organic and bio-organic materials and silicon-based semiconductors. Both pyrolysis of diacyl peroxides (Linford Chidsey, 1993) and Lewis acid-catalyzed hydrosilylation of alkenes and direct reaction of alkylmagnesium bromide (Boukherroub et al, 1999) on freshly prepared Si(lll)-H produce surfaces with similar characterishcs. These surfaces are chemically stable and can be stored for several weeks without measurable deterioration. Thienyl MLs covalently bonded to Si(l 11) surfaces have also been obtained, in which a Si(l 11)-H surface becomes brominated, Si(lll)-Br, and is further reacted with lithiated thiophenes (He etal, 1998). 

Aldehyde imines derived from alkoxyamines are metalated by LDA (0 °C, TIIF, 1 h6 or —23 °C, THF, 0.5 h13) and by potassium diethylamide, lithium bis(trimethylsily])amide and lithium 2,2,6,6-tetramethylpiperidide (—23 °C, THF, 2-4 h)1J. Nucleophilic bases such as alkyl- and aryllithium derivatives and, in some cases, alkylmagnesium bromides add to aldehyde imines. Best enantioselectivities are achieved with lithium 2,2,6,6-tetramethylpiperidide (LTMP)13. The... 

For addition of liquid bromine, a 5-mL piston burette was used delivering 0.4629 p.L s . In the calorimeter was placed 400 mL of a 0.4 M alkylmagnesium bromide in diethyl ether. The measuring procedure followed the same principles as used for HBr addition. 

An alternate synthesis is outlined in Scheme 2.1 2 Diisopropyl dichloromethylboronate (6) is readily prepared by reacting triisopropyl borate with dichloromethyllithium prepared in situ. 20 Transesterification with a suitable C2 symmetric diol gives an ester 7 that can be treated with an alkylmagnesium bromide to yield chloride 8 and then, after transesterification with pinanediol (see Section 15.1.7.2) a product 9 which is analogous to 3. 

Further examples of thiophilic addition of methyllithium and carbophilic addition of allyl- or benzyllithium and allyl Grignard reagents with 1,3-thia-zole-5(4ff)-thiones were reported [143]. Perfluorodithioesters were reacted with alkylmagnesium bromides, providing a new entry to perfluoroketene... 

R-MgBr (alkylmagnesium bromide, alkyl Grignard) Methylmagnesium bromide (methyl Grignard) Strong nucleophile when R is not bulky. Sn2/Sn2 displacements, addition reactions, addition-elimination reactions... 

Disproportionation products are postulated to arise from alkyliron(lll) and/or dialkyliron(lll) species formed by an analogous metathesis between iron(III) species and alkylmagnesium bromide. Thus, the disproportionation processes may proceed as follows (vide infra) ... 

Aldehydes, from alkylmagnesium bromides. Aliphatic Grignard reagents react with I eq. of TMBI in THF to give alditnines i(), which on hydrolysis (oxalic acid)... 

Alkylqumazolines 5 are prepared by the reaction of quinazoline with the corresponding alkylmagnesium bromides followed by potassium hexacyanoferrate(III) oxidation without isolation of the respective 3,4-dihydro derivatives" ° (cf. pp 86,165). 

Ethyl 3-ethoxy-a-nitroacrylate with 1,1-diphenylhydrazine in ethanol followed by heating has been shown to give l,4-bis(diphenylamino)-2,5-diethoxycarbonyl-l,4-dihydropyrazine (1586). A small amount of 2,5-dicyano-l,4-bis(dimethylamino)-1,4-dihydropyrazine was obtained from the reaction of 2-chloro-3-(2, 2-dimethyl-hydrazino)propionitrile [(Me)2NNHCH2CH(Cl)CN] with sodium hydride (1587). Hexaalkyl-l,4-dihydropyrazines and other 1,4-dialkyl-1,4-dihydropyrazines can be obtained by thermolysis of the products of reaction of a-(alkylamino)carboxylic acid esters with alkylmagnesium bromide. Thus the reaction of ethyl a-s-butyl-aminopropionate with ethylmapesium bromide, followed by heating in vacuo to 250-300°, gave 2,5-dimethyl-3,6-diethyl-l,4-di-s-butyl-l,4-dihydropyrazine (1588). 

In some cases, it is possible to couple an alcohol with an organometallic compound. Allylic alcohols are coupled with alkylmagnesium bromides in the presence of Ti(OiPr)4, for example. Allylic alcohols can be coupled with arylboronic acids in ionic liquid solvent and a rhodium catalyst. The palladium-catalyzed... 

Table 5 Pseudo-First-Order Rate Constants for the Reactions 0.1 M Azobenzene with 0.5 M Alkylmagnesium Bromide in Diethyl Ether at 20 C [25]...

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