Zinc alkyls Methyl

Neither reaction excludes the other, nor are these the only routes possible. The oxidation of alkylanions on a metallic anode is likely. Other processes are more clearly indicated when, instead of Cd, Zn is used as a cathode. In the latter case, zinc alkyls R2Zn and RZnI are formed by cathodic reaction of RI. This allows an efficient preparation of R4M where M = Pb, Sn and R = propyl, butyl or pentyl39, in contrast to the cathodic reduction of alkyl halides which is practically limited to the methyl and ethyl groups. 

In fact it can be assumed that, in the catalytic system TiCl4-bis[(S)-2-methyl-butyl]-zinc, dialkyl zinc alkylates the titanium atom (19) and that the titanium alkyl thus formed gives more stable complexes with the (S) olefin than with the (R) olefin, thus favouring the adsorption and polymerization of the (S) antipode (104). The influence exerted by the asymmetric groups bound to transition metals on the type of complexes formed by olefins with the same metal atom, has been recently investigated by Pajaro, Corradini, Palumbo and Panunzi (90). 

This reaction only occurs with zinc methyl and zinc ethyl with the higher zinc alkyls the aldehydes are reduced to the corresponding alcohols (B.. 17, R., 318 A., 223, 162). 

If in the second stage another zinc alkyl be used, tertiary alcohols con-taming two or three different alkyl groups can be prepared (A., 175, 374 188,110,122 0., 1910, II., 1201). Only zinc methyl and zinc ethyl thus furnish tertiary alcohols zinc propyl produces only those of the secondary type (B., 16, 2284 24, R., 667). The historical importance of the acid chloride method lies in the fact that in 1864 it led to the discovery of tertiary alcohols. 

Starting with three pounds each of the zinc diethyl and ethyl silicate, Ladenburg prepared all of the ethylethoxysilanes and described their properties. He also was able to show that the reaction was not a simple reduction of ethoxy groups to ethyl groups by the action of sodium, for methyl silicate and zinc ethyl gave e %imethoxysilanes. It is probable that the sodium reacted first with the zinc alkyl, as proposed by Ladenburg,... 

The first organic compound of boron was isolated by Frankland in 1862, by the interaction of zinc methyl and triethyl borate. This method and the use of zinc alkyls with boron trichloride was continued until the discovery of the Grignard reagent. In 1900 boron tri-methyl was prepared by the action of magnesium methyl iodide on trimethyl borate, and in 1921 a number of boron trialkyls were obtained by the interaction of magnesium alkyl halides and boron trifluoride. Of the derivatives of the type RgB, boron trimethyl is a gas, spontaneously inflammable in air boron triethyl, a spontaneously inflammable liquid whilst the higher members of the series are liquids, readily oxidised when exposed to air. The metl yL fpd ethyl derivatives combine with ammonia to foriii IliS type I BOH only... 

The isolation and characterization of these dialkylzinc compounds paved the way for the development of organometallic chemistry. Frankland and others quickly found that methyl and ethyl groups could be transferred from the zinc alkyls to other metals and metalloids. This will be discussed in the following section. 

TV-Methylprolinol 17 was obtained by the reduction of A -benzyloxycarbonylproline or N-tert-butoxycarbonylproline methyl ester with lithium aluminum hydride19. The compound was used as catalyst for the addition of zinc alkyls to carbonyl compounds (Section D.1.3.1.4.) and is also commercially available. 

Ketones can be prepared by the replacement of the halogen atom of an acyl halide (e.g. CH3COCI) by an alkyl group. This replacement can be effected as the result of the action of certain organic compounds which contain metals. The zinc alkyls or magnesium alkyl halides are generally used. Methyl ethyl ketone can be prepared in this way from acetyl chloride and magnesium ethyl iodide —... 

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. ... 

The polymerization kinetics were studied in detail. It appeared that the rate of reaction decreased as the concentration of complex increased. This anomalous behavior was explained in terms of the ability of all the zinc atoms in the complex to form coordination complexes with propylene oxide monomer, but only the inner methoxyls were effective in opening the oxirane ring of monomer coordinated with the central zinc atom. In support of this explanation, it is noted that neither diethylzinc alone nor ethylzinc methoxide initiate propylene oxide polymerization under the conditions described here however, both will form complexes with propylene oxide, about two methyl oxiranes per zinc. Addition of either zinc alkyl to Tsuruta Catalyst/... 

Alkyl Isoquinolines. Coal tar contains small amounts of l-methylisoquinoline [1721-93-3] 3-methylisoquinoline [1125-80-0] and 1,3-dimetliylisoquinoline [1721-94-4J. The 1- and 3-methyl groups are more reactive than others in the isoquinoline nucleus and readily oxidize with selenium dioxide to form the corresponding isoquinoline aldehydes (174). These compounds can also be obtained by the hydrolysis of the dihalomethyl group. The 1- and 3-methyhsoquinolines condense with benzaldehyde in the presence of zinc chloride or acetic anhydride to produce 1- and 3-styryhsoquinolines. Radicals formed by decarboxylation of carboxyUc acids react to produce 1-aIkyhsoquinolines. 

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) ... 

Butyl acrylate has been prepared by direet esterifieaLion/ by debromination of -butyl ,/3-dibromopropionate with zinc, by treatment of either butyl /3-chloropropionate or butyl /3-bromopropionate with diethylaniline, and by the pyrolysis of butyl (3-acetoxypropionated Direct esterification and alcoholysis of methyl or ethyl acrylate have been recommended for the preparation of the higher alkyl acrylates. ... 

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