Carbomagnesiation reactions alkenes

Titanocene dichloride also catalyzes a regioselective carbomagnesiation of alkenes 187 (equation 115) and dienes 188 (equation 116). The reaction proceeds at 0°C in THF in the presence of Cp2TiCl2, an organic halide and n-BuMgCl which leads to the catalytic species, affording benzyl, allyl or a-silyl alkylmagnesium halides, which are trapped with electrophiles (equation 117) . ... 

The carbomagnesiation of alkenes has been extensively investigated in the last 40 years and several reactions with high synthetic potential have been discovered. The addition of Grignard reagents to non-functionalized alkenes usually requires severe reaction conditions and only the zirconium-catalyzed... 

Although carbomagnesiations of disubstituted alkenes proceeds sluggishly, the reaction of endo-5-norbornen-2-ol (5) proceeds in high yield and regioselectivity. However, the reactivity and regioselectivity are decreased in the reaction of the methyl ether of 5. 

Somewhat related to cross-coupling reactions, the carbomagnesiation of terminal alkenes was shown to proceed efficiently in the presence of [(IMes)AgCl] and 1,2-dibromoethane, which was used as an oxidant. The hydroboration of terminal alkynes was also achieved using [(NHC)Ag] catalysts, and with higher regioselectivity compared to copper catalysis conditions. 

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