Carbon-carbon bond forming reactions based upon late-transition metal (late-TM) catalysed cross-coupling protocols have revolutionised modern synthetic chemistry. These transformations play pivotal roles in the production of many important modern-day commodities including: pharmaceuticals; agrochemicals; advanced materials; and natural products. Despite the phenomenal utility of these protocols, late-TM catalysis has a number of undesirable aspects, namely, the associated cost of expensive late-TMs, their relative toxicity and the security of the supply chain. This presentation will focus upon our recent work on the direct Csp2-Csp3 cross-coupling of diarylzinc reagents with benzylic, 1°, 2° and 3° alkyl halides (see Figure 1). In weakly-coordinating solvents, cross-coupling proceeds rapidly at ambient temperature with benzylic, 2° and 3° alkylhalide substrates without the addition of an external catalyst. The Csp2-Csp3 cross-coupling has broad functional group tolerance and products form in excellent isolated yields, generally without the requirement for purification by chromatography. Key factors which influence reactivity including choice of solvent and the relative composition of the diarylzinc reagent employed will be discussed in detail as well as mechanistic probes for radical / carbocationic mediated reactivity and control reactions which exclude the influence of non-innocent trace late-TM impurities.

Direct Csp2-Csp3 cross-coupling of diarylzinc reagents with 1°, 2° and 3° alkylhalides

249th National Meeting (2015)

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