Cross-coupling halides with organometallic compounds

Fig. 1 Iron-catalyzed cross-coupling of alkyl halides with organometallic compounds...

Carbonylative cross-coupling reactions of organometallic compounds with organic halides have been extensively studied and reported to provide excellent methods for the synthesis of unsymmetrical ketones [86]. The general catalytic cycle for this carbonylative coupling reaction is analogous to that of nucleophile except for the transmetalation step (Scheme 9.21). 

The stereodefined alkenyl halides are of prime importance due to the recent developments of di- or trisubstituted alkene synthesis by cross-coupling reactions between organometallics and alkenyl halides catalyzed by transition metal compounds 171). These alkenyl halides can be conveniently obtained from alkenylboranes or alkeneboronic acids. B-Alk enylcatecholboranes undergo rapid hydrolysis when stirred with excess water at 25 °C (Eq. 109)102). The alkeneboronic acids are usually crystalline solids of low solubility in water and can be easily isolated and handled in air without significant deterioration. 

Another, mechanistically closely related reaction is the cross-coupling reaction of aryl, benzyl, vinyl, or allyl halides with organometallic coupling reactions, such as Grignard reagents or, preferably, less reducing organometallics such as tin compounds or boronic acids RB(OH)2 the latter allow the reaction to be conducted even in aqueous media.83 The principal reaction steps are ... 

Netherton MR, Fu GC. Nickel-catalyzed cross-couplings of unactivated alkyl halides and pseudohalides with organometallic compounds. Adv. Synth. Catal. 2004 346 1525-1532. 

The formation of unsymmetric biaryls via catalytic cross-coupling of aryl halides and organometallic compounds has been shown to proceed in ionic liquids with enhanced activity. The Suzuki-Miyaura cross coupling (cf. Section 2.11)... 

Oxidative addition of aryl (or vinyl) halide to Pd(0) precursor forms the monoarylpalladium complex that is the common intermediate in the catalytic cross-coupling reactions of haloarene with organometallic compounds of main group elements such as Mg, Si, and Sn. Alkynylcopper, formed from alkyne, Cu(I) salt and base in the reaction mixture, transfers the ligand to the above Pd complex, giving an intermediate complex with aryl (or vinyl) and alkynyl ligands bonded to Pd. Reductive elimination of arylacetylene (or enyne) occurs... 

Pd-catalyzed cross-coupling reactions of organozinc compounds with alkenyl and aryl halides can be carried out under mild conditions and are the fastest among all reactions using various organometallics. The reaction with acyl hahdes is not an exception. Usually, the reaction is completed at lower than room temperature within a couple of hours [38,251 - 25 3]. As organozinc compounds are coordinatively unsaturated and sterically less bulky, the transmetallation step is facilitated [29] ... 

The stereodefined alkenyl halides are of prime importance due to the developments of di- or trisubstituted alkene synthesis by cross-coupling reactions between organometallics and alkenyl halides, catalyzed by transition metal compounds [1-4]. 1-Halo-l-alkenes are conveniently synthesized via hydrobo-ration-halogenation reaction [5]. However, with these methods it is not possible to synthesize 2-halo-1-alkenes. Although the halometalation reaction is considered to be a powerful tool for the synthesis of 2-halo-1-alkenes, the reaction has not been adequately developed for such purpose [6]. Lappert and coworkers [7-10] are perhaps the first to report the systematic haloboration reactions of unsaturated hydrocarbons with BX,. However, there is no systematic approach to the haloboration with B-X-9-BBN to organic synthesis [11]. The desired B-X-9-BBN is prepared [12] by the reaction of 9-BBN with phosphorous pentachlo-ride, bromine, or HI. Alternatively, B-X-9-BBN are very conveniently obtained... 

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