Grignard reagents with acid derivatives

Reaction of Grignard reagents with sulphonate derivatives of methyl D-ribofuranoside leads to rearranged, branched-chain sugars as outlined in Scheme 4 anomerization of these compounds by acidic methanolysis or with Grignard reagents was also studied, the latter favouring the thermodynamically less-stable anomers. ... 

TABLE 8. Formation of sulphoxides, R2S=0, from the reaction of Grignard reagents with sulphurous acid derivatives, SOX2... 

The most conspicuous property of aliphatic amines, apart from their fishy smell, is their high basicity, which usually precludes N-alkylations under acidic reaction conditions (last reaction, Scheme 6.3). Hence, alkylation of amines with tertiary alkyl groups is not usually possible without the use of highly stabilized carbocations which can be formed under basic reaction conditions. Rare exceptions are N-alkyla-tions of amines via radicals (Scheme 4.2), copper-catalyzed propargylations (Scheme 6.3), and the addition of amines to some Michael acceptors and allyl palladium or iridium complexes. Better strategies for the preparation of tert-alkylamines include the addition of Grignard reagents to ketone-derived imines [13] or the reduction of tert-alkyl nitro compounds. 

As with other halogenation processes, the monoiodination of imidazole has proved to be a difficult process. A number of recent approaches have shown some success. Thus, imidazoles can be monoiodinated at C-2 via the 2-lithio derivative or Grignard reagent. With iodine and iodic acid 5-chloro-l-methylimidazole was converted to a mixture of 12.8% of the 2,4-diiodo compound and 27.5% of the 4-iodo product. The previously undescribed 2-iodoimidazole (119) has been prepared in low yield by the sequence shown in Eq. (27). ... 

THF is useful in the malonic ester synthesis since it dissolves many sodio derivatives. Use of aqueous THF facilitates diazotization of salts of aminopolyphenyls which are sparingly soluble in water and is recommended also for the Schiemann reaction. It is superior to ether as solvent for coupling of an acetylenic Grignard reagent with a propargylic halide. Cremlyn and Chisholm found THF superior to dioxane or Cellosolve as solvent for the hydrogenation of cholesterol at ordinary temperature and pressure with perchloric acid as catalyst. 

Formation and equilibration of allylic metal derivatives such as those from the allylic bromides 24 and 25 we have just made. Reaction of the Grignard reagent with C02 gives only 27 but displacement of bromide with cyanide leads to the isomeric acid -28 both in good yield.5... 

The procedure has also been applied to halobenzoic acids.3 Thus p-bromo-benzoic acid (6) was converted into the corresponding 2-oxazoline (7) as usual, and then into the Grignard derivative (8). This is, in effect, an aryl Grignard reagent with a protected carboxyl function. Reaction with an electrophile, for example benzonitrile, gives (9). The final step is hydrolysis. If carried out in 5-7% ethanolic sulfuric acid, the ester (10b) is obtained if carried out in an aqueous medium, the free acid (10a) is obtained. 

Phenols have been derived by the oxidation of aryltriethoxysilanes in methanol with 3-chloroperbenzoic acid at ambient temperature during 24 hours (ref.40), the first step consisting in the reaction of an aryl Grignard reagent with a tetrahalogenosilane. 

---