Traditional cross-coupling reactions going ‘green’ None of these would typically be thought of as amenable to use in pure water especially at ambient temperatures, p K a issues aside, if for no other reason than that organic substrates are not normally soluble in water. And while the presence of varying percentages of water is not an issue for Heck reactions that lead ( 2– 4) to products such as cinnamates, and Suzuki-Miyaura reactions that afford ( 5– 7), for example, arylated aromatics, the far more basic nature of organozinc halides (RZnX R = alkyl) ( 8– 11) in Negishi couplings ( 12, 13) that give products such as alkylated aromatics precludes their use under aqueous conditions. However, palladium eventually gained in popularity, and in 2010 with the recognition of Heck, Suzuki and Negishi as Nobel Prize recipients ( 1), the importance of Pd-catalysed carbon-carbon bond-forming reactions in organic synthesis was confirmed.Įach modern organic synthetic reaction was developed along traditional lines that is, the chemistry was matched, not surprisingly, to an organic solvent in which the coupling best took place ( Scheme I). Decades ago, before palladium-catalysed cross-couplings arrived, copper was the transition metal of choice for mediating carbon–carbon bond formation, regardless of which organometallic complex was used as the precursor to arrive at various Cu(I) reagents.
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