Reaction screening in multiwell plates: high-throughput optimization of a Buchwald-Hartwig amination

Chemical space is vast, and chemical reactions involve the complex interplay of multiple variables. As a consequence, reactions can fail for subtle reasons, necessitating screening of conditions. High-throughput experimentation (HTE) techniques enable a more comprehensive array of data to be obtained in a relatively short amount of time. Although HTE can be most efficiently achieved with automated robotic dispensing equipment, the benefits of running reaction microarrays can be accessed in any regularly equipped laboratory using inexpensive consumables. Herein, we present a cost-efficient approach to HTE, examining a Buchwald-Hartwig amination as our model reaction. Experiments are carried out in a machined aluminum 96-well plate, taking advantage of solid transfer scoops and pipettes to facilitate rapid reagent transfer. Reaction vials are simultaneously heated and mixed, using a magnetic stirrer, and worked up in parallel, using a plastic filter plate. Analysis by gas chromatography provides the chemist with 96 data points with minimal commitment of time and resources. The best-performing experiment can be selected for scale-up and isolation, or the data can be used for designing future optimization experiments.