Grignard reagent cross coupling

Alkenes from vinyl iodides and Grignard reagents. Cross coupling of vinyl iodides with Grignard reagents to form alkenes is possible with catalysis by this palladium complex. Yields are 80-877o (six examples). Of more interest, the reaction occurs almost exclusively (>97%) with retention of configuration (equation I). 

Sequential cross-coupling can be used also for synthesis of 1,1-disubstituted alkenes from 2,3-dibromopropene (Aldrich). The allylic halogen couples directly with a Grignard reagent vinylic coupling is slower and requires a catalyst (equation I). 

Nickel (II) Catalyzed Cross-Coupling with Grignard Reagents (Kumada Reaction) Pure AppJ. Chem. 1980, 52, 669 Bull Chern. Soc.Jpn. 1976, 49, 1958... 

These aryl—aryl couplings are appHcations of the Ni(0) and Ni(II)-cataly2ed cross-couplings of unreactive organic haUdes with Grignard reagents. This work has been extensively reviewed (90). 

Alkyl- and aryl-pyridazines can be prepared by cross-coupling reactions between chloropyridazines and Grignard reagents in the presence of nickel-phosphine complexes as catalysts. Dichloro[l,2-bis(diphenylphosphino)propane]nickel is used for alkylation and dichloro[l,2-bis(diphenylphosphino)ethane]nickel for arylation (78CPB2550). 3-Alkynyl-pyridazines and their A-oxides are prepared from 3-chloropyridazines and their A-oxides and alkynes using a Pd(PPh3)Cl2-Cu complex and triethylamine (78H(9)1397). 

Geranyltrimethylsilane, 142 Grignard cross-coupling, asymmetric, 31 Grignard reaction, 39,63 Grignard reagent, 45,58,120,121... 

TABLE IRON CATALYZED CROSS COUPLING REACTIONS OF GRIGNARD REAGENTS WITH (HETEROJARYL CHLORIDES OR -TRIFLATES... 

Cross-Coupling of Arylchloridcs with Aryl Grignard Reagents... 

CROSS-COUPLING OF ARYLCHLORIDES WITH ARYL GRIGNARD REAGENTS (KUMADA REACTION)... 

Scheme 29 Iron-catalyzed cross coupling reaction of aryl Grignard reagents with alkyl halides...

Although the formation of tetraalkylferrates, for example, in the first step of a cross-coupling reaction starting from Fe(-i-3)-salts and alkyl Grignard reagents, seems possible, until now there is no analytical or spectroscopic proof for such a species. In fact, it was shown that Fe(-i-3) is reduced by MeLi or MeMgBr to Fe(-i-2) under release of ethane [5, 6]. 

A tandem cyclisation/cross-coupling reaction between 6-halo-1-hexene 82 and Grignard reagents 83 is successfully catalysed by a NHC-Co catalytic system (Scheme 5.23) [23]. 

TABLE 3. Cross-coupling reaction of vinyl sulfones with Grignard reagents ... 

Nickel(II) salts are able to catalyze the coupling of Grignard reagents with alkenyl and aryl halides. A soluble 6 -phosphine complex, Ni(dppe)2Cl2, is a particularly effective catalyst.266 The main distinction between this reaction and Pd-catalyzed cross... 

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