Halides, aryl, arylation metal catalyzed alkylation

Stereoselective synthesis of 1,4-dienes This Pd complex markedly catalyzes the cross-coupling of alkenyl and aryl metals containing Al, Zr, or Zn with allylic halides, but not of alkyl metals. The coupling is markedly stereo- and regioseleclive. Examples ... 

Scheme 1.5. Mechanism of transition metal-catalyzed cross-coupling of an aryl halide with a metal alkyl.

Metal Enolates. In parallel with additives, transition metals may be added to enolates to give transmetallated species which can undergo cross-coupling chemistry. Perhaps the earliest example of metal-catalyzed enolate reactions is the Reformatsky reaction. Transition metal-catalyzed enolate chemistry has been recently revived in the literature, particularly in the field of asymmetric catalysis. The transition metal-catalyzed coupling reactions of aryl halides, allyl epoxides, and allylic esters with alkyl enolates have been recently investigated. Generally the choice of base employed depends on the substrate and on the reaction performed. For enolate arylation, KHMDS seems to be the most... 

Among many substrates used for Pd(0)-catalyzed reactions, organic halides are most widely used. In Grignard reactions, Mg(0) metal reacts with organic halides of sp carbons (alkyl halides) more easily than halides of sp carbons (aryl and alkenyl halides). On the other hand, Pd(0) complexes react more easily with halides attached to sp carbons, namely aryl and alkenyl halides. In addition, several pseudohalides are used as well. They undergo facile oxidative addition to Pd(0) to form Pd complexes which have cr-Pd-carbon bonds. Scheme 3.1 summarizes the oxidative addition of phenyl halides and pseudohalides to form phenylpalladium halides. Aryl iodides and bromides have been used widely. 

Metal-Catalyzed Arylations of Nonactivated Alkyl (Pseudo) Halides via Cross-Coupling Reactions... 

Table 5.1 Palladium-catalyzed cross-coupling reactions between unactivated alkyl halides and aryl metal reagents.

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