Manganese compounds allyl

In a similar manner, Jt-allyl complexes of manganese, iron, and molybdenum carbonyls have been obtained from the corresponding metal carbonyl halides [5], In the case of the reaction of dicarbonyl(r 5-cyclopentadienyl)molybdenum bromide with allyl bromide, the c-allyl derivative is obtained in 75% yield in dichloromethane, but the Jt-allyl complex is the sole product (95%), when the reaction is conducted in a watenbenzene two-phase system. Similar solvent effects are observed in the corresponding reaction of the iron compound. As with the cobalt tetracarbonyl anion, it is... 

Hwu et al. have examined the dependence of the metal oxidant on the mode of reactivity in silicon-controlled allylation of 1,3-dioxo compounds [95JOC856]. The use of manganese(III) acetate furnished the dihydrofuran product 22 only. On the other hand, use of cerium(IV) nitrate resulted in the formation of both acyclic (23) as well as the cyclized compound, with the product distribution dependent on the nature of the allylsilane. Facile synthesis of dihydrofurans by the cerium(IV) mediated oxidative addition of 1,3-dicarbonyl compounds to cyclic and acyclic alkenes has also been reported [95JCS(P1)187]. 

In a thorough study it was determined that the Barbier coupling of allylic halides 69a to aldehydes, ketones, or a,p-unsaturated carbonyl compounds 68 catalyzed by Cp2TiCl2 47a in the presence of manganese as the terminal reducing agent proceeds most likely via a radical mechanism (Fig. 21) [149,150], The active titanocene(III)... 

Reduction of Cp2TiCl2 with metallic manganese generates Ti(m) catalysts for the addition of allyl bromide to carbonyl compounds. This method can be used for asymmetric reactions if Brintzinger s compound r -(ebthi)2TiCl2 or the previously synthesized chiral derivative1175 shown in Scheme 492 are used. When chiral bis-Cp complexes are employed, acceptable yields of optically active products are obtained.1176... 

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