Grignard reagents reactions with electrophiles

Attention should be paid to the reactivity of 1 and 11, which react with nucleophiles. It is well known that Grignard reagents react with electrophiles forming Mg(II), whereas Pd complexes generate Pd(0) after reacting with nucleophiles. Grignard reactions cannot be carried out catalytically, because it is difficult to reduce Mg(II) to Mg(0) in situ. However, formation of Pd(0) by the reaction of nucleophiles shows the possibility of catalytic reactions. This is the most important characteristic of Pd chemistry. Ni compounds react with both electrophiles (stoichiometric) and nucleophiles (catalytic), depending on the substrates. 

The furoxan ring is more susceptible to nucleophilic attack and reduction than it is to reaction with electrophiles or oxidation. Grignard reagents react with disubstituted furoxans primarily at C-3 and, in most cases, the resulting adduct fragments to a nitrile and a nitronate salt which affords a ketone on workup. 

The perfluoroalkyl Grignard reagents participate in a wide variety of functionalization reactions with electrophiles as illustrated in Scheme 9 [27-35]. 

Heterocyclic aromatic compounds such as pyrrole are readily metallated with Grignard reagents. The resulting compounds have N"Mg bonds and are, therefore, not organometallic compounds, but on reaction with electrophiles give 2-substituted pyrroles [14] (eq (4)). The reaction of chloroform or bromoform with PrMgCl at -78 °C in THF-HMPA (4 1) is mild and convenient method for the generation of an unstable carbenoid in the solution [15] (eq (5)). 

Grignard reagents react with epoxides to form a new carbon-carbon bond and open the three-membered ring, but there are two electrophilic carbon atoms. The final product after hydrolysis is an alcohol. The Grignard reagent attacks the less hindered carbon in an Sn2 like reaction. 3 If the carbons of the epoxide moiety are primary or secondary, attack can occur at either carbon leading to a mixture of alcohol products. 

---