Zinc alkyls dimethyl

Many other electrophiles are able to react with metalated ferrocenylalkyl amines, e.g., trimethyl borate (Fig. 4-27 a), which gives, after hydrolytic workup, compounds like (S,S)-l-(iV,iV-dimethyl-l-aminoethyl)ferrocene-2-boronic acid [106]. Important intermediates for further derivatization are the halogens. For the lithiation technique, I2 (Fig. 4-27b) [151] and BrCN [106] lead to the desired compounds, but when BrCN is used, partial substitution of the dimethylamino group by cyanide occurs (see Sect. 4.3.3.2 and Fig. 4-17). For palladated amines, Brj is applicable [152]. (i ,S)-l-Iodo-2-(iV,iV-dimethyl-l-aminoethyl)ferrocene is the starting material for catalytically active zinc compounds for the enantioselective addition of zinc alkyls to carbonyl compounds [151] (see Chapter 3 for this topic). 

S)-l-Benzyloxycarbonyl-2-[hydroxy(diphenyl)methyl]pyrrolidine [(S)-25] was used as an auxiliary in the enantioselective reduction of carbonyl compounds to secondary alcohols (Section D.2.3.2.) it is prepared analogously to the a,a-dimethyl derivative25. The A -methyl derivative (S)-26 (DPMPM) is among the most selective catalysts for the addition of zinc alkyls to carbonyl compounds (Section D.1.3.1.4.). 

Frankland used a copper pressure vessel in the preparation of zinc ethyl from zinc and ethyl iodide. PebaF described the preparation of zinc alkyls. Frankland and Duppa prepared zinc methyl by the action of excess of zinc on mercury dimethyl. J. H. Gladstone and A. Tribe acted upon methyl iodide with a zinc-copper couple, which they introduced as a reducing agent. Many chemists described alternative methods of preparation of zinc ethyl, which, before the discovery of the Grignard reagent (see p. 858), was one of the most extensively used compounds in organic syntheses. ... 

Synonims quaternary ammonimn compounds, bis(hydrogenated tallow alkyl)dimethyl, salts with bentonite, bentonite, montmorillonite copper phthalocyanine Pigment Blue 15 tungsten disulfide zinc oxide -i- 1,3,5-benzene tricaboxylic-(N-4-ll uorophenyl)triamine... 

Many organic hahdes, especially alkyl bromides and iodides, react direcdy with tin metal at elevated temperatures (>150° C). Methyl chloride reacts with molten tin metal, giving good yields of dimethyl tin dichloride, which is an important intermediate in the manufacture of dimethyl tin-ha sed PVC stabilizers. The presence of catalytic metallic impurities, eg, copper and zinc, is necessary to achieve optimum yields (108) ... 

It is deposited by MOCVD, with an alkyl precursor, such as dimethyl zinc and tetrahydrofuran (THF) f l... 

The basic assumption is made in these calculations that the benzyl or phenyl radicals formed are removed in the hot zone only by recombination with methyl radicals. When dimethyl zinc is used, the apparent energy of activation for reaction (11) is negative indicating a loss of phenyl radicals in the hot zone by an additional process. The only species present which is absent when the mercury and cadmium alkyls are used is ZnCH3. The additional process by which phenyl radicals are lost is therefore probably... 

Fig. 2. Arrhenius plots for the decomposition of dimethyl zinc. 1, Price and Trotman-Dickenson solid line, 16 torr toluene dotted line, 5 torr toluene 2, Lambert, approx. 760 torr (cyclohexane +7 % alkyl) 3, composite curve obtained from rate coefficients of Price and Trotman-Dickenson corrected to infinite pressure and from Lambert s values. The composite curve has been displaced upwards by 2.0 log units. Open circles Topor, 22-24 torr (argon+2.4 torr dimethyl zinc). 

Fig. 5. The Arrhenius plot of kl/k2i. e, dimethyl zinc O, trimethyl gallium , trimethyl indium. % figures are in terms of the theoretical yield of methyl radicals that would be obtained if all methyl-metal bonds were broken. All points are corrected to 13 torr pressure (toluene+0.3-2.5 % alkyl).

Primary alkyl radicals have been generated from alkyl iodides (RCH2I) using dimethyl-zinc and air as initiator the radicals can then be used to alkylate iV-tosylimines, ArCH=NTs, to give the corresponding amines, ArCH(CH2R)NHTs42 The latter process is promoted by BF3 etherate and catalysed by copper(II). 

One of these differences is that if a methylated derivative of any particular metal-containing compound should be desired, there is a rich and diverse variety of potentially suitable alkyl-donating agents available from which the most effective can be chosen. Classic examples of methyl donors include Grignard reagents and species such as methyl lithium, dimethyl zinc, or trimethyl aluminum compounds. 

As a model study of methyl cobalamine (methyl transfer) in living bodies, a methyl radical, generated by the reduction of the /s(dimethylglyoximato)(pyridine)Co3+ complex to its Co1+ complex, reacts on the sulfur atom of thiolester via SH2 to generate an acyl radical and methyl sulfide. The formed methyl radical can be trapped by TEMPO or activated olefins [8-13]. As a radical character of real vitamin B12, the addition of zinc to a mixture of alkyl bromide (5) and dimethyl fumarate in the presence of real vitamin B12 at room temperature provides a C-C bonded product (6), through the initial reduction of Co3+ to Co1+ by zinc, reaction of Co1+ with alkyl bromide to form R-Co bond, its homolytic bond cleavage to form an alkyl radical, and finally the addition of the alkyl radical to diethyl fumarate, as shown in eq. 11.4 [14]. 

Electrochemical reduction of the salts (4) provides radicals (18) which dimerize or undergo further reduction to anions (32) or dianions (80MI43100). The reduction potentials are not much affected by substituents. Reduction with zinc in aprotic conditions gives bi(l,2-dithiol-3-yls) (59), and 3-chloro-l,2-dithiolylium salts (35a X = Cl) are converted into bi(l,2-dithiol-3-ylidenes) (20) (75TL3473). Divalent chromium converts the 3,5-dimethyl-l,2-dithiolylium cation into a dithioacetylacetonate ligand (72AJC2547). The reaction of 3,5-diamino-l,2-dithiolylium salts (8) or alkyl derivatives with thiols provides dithiomalonamides (60) by electron transfer (63ACS163). 

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