Grignard reagents arylation

Synthetic applications requiring water-free conditions, such as reactions with Grignard reagents, aryl and alkyl aluminum... 

Aryl Grignard reagents usually give better yields in these reactions than alkyl Grignard reagents. Aryl triflates couple with arylmagnesium halides in the presence... 

Grignard reagents (aryl, vinyl, or alkyl) can be electrograted by oxidation on Si-H to give 5f-alkyl, vinyl, or aryl mnltilayers through the formation of radicals [420-421]. The films are therefore quite similar to those obtained from diazonium salts. The drawback of the method lies in the necessity to work under oxygen- and water-free conditions to prevent the oxidation of Si and the hydrolysis of the reagent. 

Since Grignard reagents can easily be obtained from aryl halides, they are of special value in the s nthesis of many aromatic compounds, particularly as, for reasons already stated (pp. 270, 276), aromatic compounds cannot generally be prepared by means of ethyl acetoacetate and ethyl malonate. 

The order of halide reactivity is I > Br > Cl > F and alkyl halides are more reac tive than aryl and vinyl halides Indeed aryl and vinyl chlorides do not form Grignard reagents m diethyl ether When more vigorous reaction conditions are required tetrahy drofuran (THF) is used as the solvent... 

Overall the carboxylation of Grignard reagents transforms an alkyl or aryl halide to a carboxylic acid in which the carbon skeleton has been extended by one carbon atom... 

The major limitation to this procedure is that the alkyl or aryl halide must not bear substituents that are incompatible with Grignard reagents such as OH NH SH or... 

Formation of aryl Grignard reagents (Section 14 4) Aryl halides react with magnesium to form the corresponding arylmagnesium halide Aryl iodides are the most reac tive aryl fluorides the least A similar reaction occurs with lithium to give aryllithium reagents (Section 14 3)... 

The reaction proceeds by formation of the Grignard reagent from o bromofluorobenzene Because the order of reactivity of magnesium with aryl halides is Arl > ArBr > ArCl > ArF the Gngnard reagent has the structure shown and forms benzyne by loss of the salt FMgBr... 

Grignard reagent (Section 14 4) An organomagnesium com pound of the type RMgX formed by the reaction of magne Slum with an alkyl or aryl halide... 

Total basicity is measured by standard acid—base titration techniques. The activity divided by the total basicity should be greater than 90%. If it is not, then the Grignard reagent should be checked for unreacted alkyl or aryl haUde, homo-coupled product, hydrolysis products, and oxidation products. 

These aryl—aryl couplings are appHcations of the Ni(0) and Ni(II)-cataly2ed cross-couplings of unreactive organic haUdes with Grignard reagents. This work has been extensively reviewed (90). 

Cesium forms simple alkyl and aryl compounds that are similar to those of the other alkah metals (6). They are colorless, sohd, amorphous, nonvolatile, and insoluble, except by decomposition, in most solvents except diethylzinc. As a result of exceptional reactivity, cesium aryls should be effective in alkylations wherever other alkaline alkyls or Grignard reagents have failed (see Grignard reactions). Cesium reacts with hydrocarbons in which the activity of a C—H link is increased by attachment to the carbon atom of doubly linked or aromatic radicals. A brown, sohd addition product is formed when cesium reacts with ethylene, and a very reactive dark red powder, triphenylmethylcesium [76-83-5] (C H )2CCs, is formed by the reaction of cesium amalgam and a solution of triphenylmethyl chloride in anhydrous ether. 

Anthocyanidins were first synthesi2ed by reaction of an aryl Grignard reagent with a coumarin (93). 

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). 

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