Aryl chlorides Negishi coupling

Scheme 6.23 Nickel-catalysed Negishi coupling between unactivated aryl chlorides and oiganozinc reagents...

A more general procedure for high-speed microwave-assisted Negishi and Kumada couplings of unactivated aryl chlorides has recently been reported by Walla and Kappe (Scheme 6.40) [82]. This procedure uses 0.015-2.5 mol% oftris(dibenzyl-... 

Both vinyl- and aryl triflates have been cross-coupled with 2-furylzinc chloride [26-28]. Since vinyl triflates are easily obtained from the corresponding ketones, they are useful substrates in Pd-catalyzed reactions. In the following example, a Negishi coupling of 2-furylzinc chloride and indol-5-yl triflate (22) provided an expeditious entry to 2-(5 -indolyl)furan (23). Protection of the NH in the indole ring was not required. A similar reaction was successful with pyridyl- and quinolinyl triflates. 

Unlike normal all-carbon aryl halides, regioselective Negishi coupling reaction of 2,3-dibromofuran 27 with 2-furylzinc chloride was achieved at C(2) to afford bisfuran 28 [35]. 

The scope of the Negishi-coupling is not limited to aryl and vinyl halides and sometimes acyl chlorides might also be converted to ketones by this protocol. The 2,3-dihalopyrrole derivative shown in 6.22. was converted into its 2-lithio derivative by selective lithium-halogen exchange at -78 °C. Addition of zinc chloride effected the formation of the appropriate pyrrolylzinc chloride, which was coupled with a functionalised butyroyl chloride in the presence of tetrakis(triphenylphosphino)palladium and furnished the expected 2-acylpyrrole in 61% yield.27... 

The selective sequential Suzuki-Negishi coupling of anisylboronic acid and /lara-mcthoxybenzylzinc chloride on 2,6-dichloro-9-isopropylpurine was also achieved (8.15.), Sequential addition of the coupling partners resulted in the selective introduction of the first aryl moiety into the 6-position followed by the introduction of the second coupling partner into the... 

R1 = N02, CN, OMe R2 = Me, OMe Scheme 71 Negishi couplings with aryl chlorides... 

Walla, P., Kappe, C. O. Microwave-assisted Negishi and Kumada cross-coupling reactions of aryl chlorides. Chem. Common. 2004, 564-565. 

ClZn" MW. 175 °C. 10 min Scheme 15.43. Negishi coupling of an aryl chloride. 

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