Alkenyl halides and Grignard

B. Iron Catalysis in the Cross Coupling of Alkenyl Halides and Grignard Reagents Grignard reagents are cross coupled stereospecifically with alkenyl halides such as 1-bromopropene in the presence of catalytic amounts of iron complexes.(27)... 

Cross coupling of alkenyl halides and Grignard reagents. This iron(III) complex is more effective than ferric chloride from the standpoint of both rate and deactivation of the catalyst. The active catalyst is actually a reduced iron(I) species. 

Pd- or Ni-catalyzed Kumada cross-coupling Cross-coupling of alkenyl- or aryl halides and Grignard reagents or organolithium species. 258... 

Alkylations. The halogen atoms of alkenyl halides and 1,1 -dichlorocyclopropanes are replaced with the organic group from a Grignard reagent in the presence of an iron complex such as Fe(acac)j and tris(dibenzoylmethido)iron(III). 

Tetrakis(triphenylphosphine)palladium catalyzes coupling of alkenyl halides with Grignard reagents and organolithium reagents. 

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 of carbons. In other words, alkenyl and aryl halides undergo facile oxidative additions to Pd(0) to form complexes 1 which have a Pd—C tr-bond as an initial step. Then mainly two transformations of these intermediate complexes are possible insertion and transmetallation. Unsaturated compounds such as alkenes. conjugated dienes, alkynes, and CO insert into the Pd—C bond. The final step of the reactions is reductive elimination or elimination of /J-hydro-gen. At the same time, the Pd(0) catalytic species is regenerated to start a new catalytic cycle. The transmetallation takes place with organometallic compounds of Li, Mg, Zn, B, Al, Sn, Si, Hg, etc., and the reaction terminates by reductive elimination. 

GRIGNARD-TYPE COUPLING REACTIONS BETWEEN ALKENYL HALIDES (OR TRIFLATES) AND ALDEHYDES, MEDIATED BY THE CrCI2-NiCI2 SYSTEM3... 

In 2002, Furstner and coworkers reported that aryl halides react with Grignard reagents under the conditions previously used for the coupling of alkenyl halides. They proposed that the active iron species is Fe(MgX)2, a complex described by Bogdanovic and coworkers ° a few years earlier (Scheme 30). This iron(-II) species is formed by addition of four equivalents of the Grignard compounds to FeCl2. 

Yamamoto and coworkers studied the substitution of ally lie phosphates by Grignard reagents in the presence of copper or iron salts. Only the Sn2 product is formed under copper catalysis whereas, in the presence of iron(III) acetylacetonate, the Sn2 product is generally obtained with an excellent selectivity (Scheme 49). It should be noted that aryl-, alkenyl-, aUcynyl- and aUcyhnagnesium halides can be used successfully. 

PHOSPHINE-NICKEL COMPLEX CATALYZED CROSSCOUPLING OF GRIGNARD REAGENTS WITH ARYL AND ALKENYL HALIDES 1,2-DIBUTYLBENZENE... 

Cross-Coupling of Grignard Reagents with Various Aryl and Alkenyl Halides in the Presf.ncf of [Ni(dppp)Cl2] as a Catalyst"... 

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