Grignard reagents iron salts

The first attempts to modify the course of the reaction of Grignard reagents with various substrates by using iron salts as a catalyst were reported by Kharasch and coworkers ... 

In 1982, JnUa s group showed that vinyl snUones react with Grignard reagents in the presence of iron salts to afford moderate yields of conpling product (Scheme 25). The reaction is stereoselective but its scope is limited. Thus, with secondary alkylmagnesium halides, only the reduction product is formed. 

Yamamoto and coworkers studied the substitution of ally lie phosphates by Grignard reagents in the presence of copper or iron salts. Only the Sn2 product is formed under copper catalysis whereas, in the presence of iron(III) acetylacetonate, the Sn2 product is generally obtained with an excellent selectivity (Scheme 49). It should be noted that aryl-, alkenyl-, aUcynyl- and aUcyhnagnesium halides can be used successfully. 

Many years later, Fukuhara and Urabe showed that aryl Grignard reagents react with ethyl 2,4-dienoates or 2,4-dienamides, in the presence of iron salts, to give the 1,6-addition products (Scheme 60). This reaction is stereoselective and leads to the (Z)-trisubstituted olefins. 

Terminal alkynes are readily deprotonated by Grignard reagents, and no further addition occurs to al-kynylmagnesium halides. In the presence of transition metal complexes of titanium,70 iron,70 rhodium,71 nickel,70 72 palladium70 or copper,73 the carbomagnesiation takes place in moderate yields. The regio- and stereo-selectivity of the additions are variable. In the presence of a copper(I) salt, however, only the syn... 

The first asymmetric iron-catalyzed conjugate addition was reported in 1977. Benzylidene malonate 56 with an ephedrine moiety as chiral auxiliary was converted with Grignard reagents such as nBuMgBr in the presence of catalytic amounts of various metal salts. The optically active phenylpropionic acid 57 was obtained with... 

Iron(III) salts, and Grignard reagent reactivity, 9, 49 Iron seleno-terephthalates, for fungus and molds, 12, 458 Iron silicides, formation, 6, 19... 

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