Transition Metal-Catalyzed Alkylative Ring-Opening

Transition Metal-Catalyzed Alkylative Ring-Opening... 

The observation that the metal carbene complex, (CO)5W = C(Ph)2 [22], catalyzed the polymerization of cyclic olefins to ring opened polymers containing the diphenylmethylene unit of the catalyst provided additional evidence that carbenes were involved in the catalytic cycle. The formation of the initiating metal carbenes in the classic systems that consist of transition metal halides and alkylating agents was proposed to involve metal alkylation followed by oc-hydrogen loss, Eq. (6). Methane and propene were detected in the early stages of these reactions [23]. 

Palladium remains the most widely recognized transition metal to effect stereoselective allylic alkylation reactions. Consequently, diastereoselective and enantioselective Pd-catalyzed processes are extensively discussed in Sections 14.2 and 14.3. More recent advances in the field of metal-catalyzed al-lylation reactions include the use of chiral iridium complexes, dealt with in Section 14.4 [33, 34]. Section 14.5 describes selected stereoselective copper-catalyzed SN2 -allylation reactions [33, 35-37], while a brief presentation of allylation reactions with other transition metals including Mo and Rh is given in Section 14.6 [8, 13, 33, 38, 39]. The closing Section 14.7 deals with selected methods for asymmetric ring-opening reactions of unsaturated heterocycles [38, 40, 41]. 

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