What the Heck? – Generic protocols and the development of catalytic reactions
The concept and evolutionary development of a generic protocol to give a fit-for-purpose and/or proof of transformation for a common transition metal catalysed reaction is discussed. The case for such protocols as the basis for further development and optimisation of these challenging reactions is presented. The use of advanced statistical techniques (DoE/PCA) to ensure the efficient planning of experimental designs and the effective interpretation of experimental results is outlined. The benefits of a custom-designed laboratory to support research and development in the field of metal catalysis are also highlighted. This combined approach can provide significant benefit for similar transition metal catalysed reactions, and indeed many other reactions.
The development of transition metal catalysed reactions can be a difficult enterprise, but is undertaken because, if successful, it yields cheaper, shorter and more sustainable synthetic routes. At CatScI, we see the role of the generic protocol for a given transition metal-catalysed reaction as key in underpinning this vital endeavour. This serves two purposes: (i) demonstrating proof of transformation, from which further optimisation can proceed if required; (ii) providing fit-for-purpose reaction conditions if full optimisation is not required.
This article exemplifies the development of a generic protocol for one of the most valuable transition metal-catalysed reactions (1), the Pd-catalysed Heck cross-coupling reaction between an alkene and an aryl bromide (Scheme 1) (2). Much development of the Heck reaction has been reported, usually focusing on new catalytic systems composed of bespoke mixtures of metal, ligand, base and solvent (3). However, such systems are typically tested on simple substrates with limited functional group diversity in the first case, and as a result, often turn out to be unsuitable for the synthesis of co ...