For each of these hit reactions, the bulk of the crude reaction mixture was purified by mass-directed HPLC, and the purified products analysed by 500 MHz 1 H NMR spectroscopy. In total, seven reactions yielded validated reaction products (dark blue squares, Figure ; see also Table and ). Next, a second reaction array was designed that was informed by the validated reactions from the initial reaction array. Here, the executed reactions, selected from the set of 4536 possible reactions, had: (a) switched which of the two substrates was in excess; (b) changed either of the substrates to another substrate from the same class (e.g. to a different alkene or hetarene); (c) switched whether or not TFA was used; or (d) switched whether the thiol additive, the oxidant or no additive was used. The designed reaction array was executed and analysed as before, and the potential hit reactions were purified and validated by 500 MHz 1 H NMR spectroscopic analysis. An additional ten reactions were found to have yielded validated reaction products, though only two of the products had not been observed previously (see Table , Figure and Supporting Information).