Cross-coupling aryl halides

Grignard and Aryl Halide Cross-Coupling Reaction 1 -Methyl-2-(methyl-d3)-benzene... 

Our group has recently developed an alternative method for alkyl-(hetero)aryl- as well as aryl-heteroaryl cross coupling reactions catalyzed by iron salts.3 4 This methodology was inspired by early reports of Kochi et al.5>6 on iron-catalyzed cross coupling of vinyl halides and is distinguished by several notable advantages. 

Aryl-alkenyl cross-coupling is straightforward. Simple alkylmagnesium reagents (Me, Et, CH2SiMe3, etc.) can be easily involved in Ni-catalyzed cross-coupling (27),139,140 while more complex alkyl halides—particularly branched ones prone to /3-hydride elimination—require Pd catalysts with bidentate phosphines, such as dppf, to achieve good selectivity (Section 9.6.3.4.7). 

In common with vinyl and aryl halides, it has now been shown that allenic and propargylic halides cross-couple with Grignard reagents in the presence of palladium catalysts. The product consists predominantly of the substituted allene... 

Meyer S, Orben CM, Demeshko S, Dechert S, Meyer F. Synthesis and characterization of di- and tetracarbene iron(II) complexes with chelating N-heterocychc carbene ligands and their apphcation in aryl Grignard-alkyl halide cross-coupling. Organometallics. 2011 30 6692—6702. 

Bica, K. Gaertner, P. (2006). An iron containing ionic liquid as recyclable catalyst for aryl Grignard cross-coupling of alkyl halides. Organic Letters, 8, 4, 733-735, ISSN 1523-7060... 

The cross-coupling of aromatic and heteroaromatic rings has been carried out extensively[555]. Tin compounds of heterocycles such as oxazo-lines[556,557], thiophene[558,559], furans[558], pyridines[558], and seleno-phenes [560] can be coupled with aryl halides. The syntheses of the phenylo.xazoline 691[552], dithiophenopyridine 692[56l] and 3-(2-pyridyl)qui-noline 693[562] are typical examples. 

The cis thioboration of terminal alkynes with 9-(arylthio)-9-BBN is catalyzed by Pd(Pli3P)4 in the presence of styrene. The product 136 is converted into the vinyl sulfides 137 and 138 by the treatment with MeOH or by Pd-catalyzed cross-coupling with aryl or alkenyl halides using K3PO4 in DMF[68]. No thioboration takes place with internal alkynes. 

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