Transmetallation in the Negishi Reaction

This work demonstrated the existence of some competitive transmetallation pathways in the Negishi coupling reaction that had not been invoked before [286b]. 

Transmetallation has been demonstrated to be the rate-hmiting step in the Sonogashira couphng reaction [291]. The transmetallation is also rate-determining in the nickel-catalyzed reaction between arylzinc reagents and a-chloro carbonyl compounds that proceeds via ArNi(II)R intermediates [292]. 

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Scheme 1.36 Transmetallation in the Negishi reaction in the presence/absence of added phosphine.

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