Grignard reagent in the preparation

Grignard reagent in the preparation of a hydrocarbon, 4, jg Grignard reagent to olefins, 6, 32 Guaiacol, 3, 28 Guanidine, 7, 69... 

Chromium hexacarbonyl is prepared by the reaction of anhydrous chromi-um(lll) chloride with carbon monoxide in the presence of a Grignard reagent. A 60% product yield may be obtained at the carbon monoxide pressures of 35 to 70 atm. Other chromium salts may be used with carbon monoxide and Grignard reagent in the preparation. The compound may also be obtained by the reaction of a chromium salt with carbon monoxide in the presence of magnesium in ether or sodium in diglyme. 

Dialkylcadmium reagents are often useful alternatives to the more reactive Grignard reagents in the preparation of ketones from acyl halides However, bis(trifluoromethyl)cadmium glyme is decomposed by acyl halides and does not give trifluotomethyl ketones [ , 124] Nevertheless, this reaction can be used as a low-temperature source of difluorocarbene [S, 124] (equation 102)... 

Pure ether for Grignard reagent. In the preparation of Grignard reagent and other work in the organic laboratory pure dry ether is required. The impurities in commercial ether are water and ethanol. Though ether and water are regarded as immiscible... 

Alkyl- and aryl-pyridazines can be prepared by cross-coupling reactions between chloropyridazines and Grignard reagents in the presence of nickel-phosphine complexes as catalysts. Dichloro[l,2-bis(diphenylphosphino)propane]nickel is used for alkylation and dichloro[l,2-bis(diphenylphosphino)ethane]nickel for arylation (78CPB2550). 3-Alkynyl-pyridazines and their A-oxides are prepared from 3-chloropyridazines and their A-oxides and alkynes using a Pd(PPh3)Cl2-Cu complex and triethylamine (78H(9)1397). 

The formation of g-alkyl-a,g-unsaturated esters by reaction of lithium dialkylcuprates or Grignard reagents in the presence of copper(I) iodide, with g-phenylthio-, > g-acetoxy-g-chloro-, and g-phosphoryloxy-a,g-unsaturated esters has been reported. The principal advantage of the enol phosphate method is the ease and efficiency with which these compounds may be prepared from g-keto esters. A wide variety of cyclic and acyclic g-alkyl-a,g-unsaturated esters has been synthesized from the corresponding g-keto esters. However, the method is limited to primary dialkylcuprates. Acyclic g-keto esters afford (Zl-enol phosphates which undergo stereoselective substitution with lithium dialkylcuprates with predominant retention of stereochemistry (usually > 85-98i )). It is essential that the cuprate coupling reaction of the acyclic enol phosphates be carried out at lower temperatures (-47 to -9a°C) to achieve high stereoselectivity. When combined with they-... 

Nevertheless Kipping made a number of contributions of value to the modem silicone industry. In 1904 he introduced the use of Grignard reagents for the preparation of chlorosilanes and later discovered the principle of the inter-molecular condensation of the silane diols, the basis of current polymerisation practice. The term silicone was also given by Kipping to the hydrolysis products of the disubstituted silicon chlorides because he at one time considered them as being analogous to the ketones. 

Alternatively, the compound can be prepared by reduction of manganese(ll) iodide with a Grignard reagent in the presence of carbon monoxide under pressure. 

Another type of chiral Michael acceptor, the oxazepine derivatives (47), is prepared by condensation of the (-)-ephedrine-derived malonic acid derivative (46) with aldehydes (Scheme 18).51 52 Treatment of (47) with a variety of Grignard reagents in the presence of NiCh affords, after hydrolysis and decarboxylation, the 3-substituted carboxylic acids (48), in most cases with more than 90% ee. Diastereoselective Michael additions to (47) were also used for the preparation of optically active cyclopropane derivatives (49)53 and P-substituted-y-butyrolactones (50 Scheme 18).54 A total synthesis of indolmycin is based on this methodology.55... 

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