The potential to control the strain-release reactivity of BCB sulfoximines with different N-groups was first investigated using 4-tert-butylthiophenol as the nucleophile in the presence of triethylamine in MeCN. The consumption of the BCB substrates was monitored by 1 H NMR with calculation of the half-life using the predicted curve of best fit. The more electron withdrawing Nsubstituents gave faster reactions with t1/2 spanning from 460 min to <3 min. The strain-release reactivity was correlated to the 13 C NMR chemical shift of the BCB terminal bridgehead position to provide a predictor for strain-release reactivity (Figure ). By comparison, Baran's p-tolyl substituted BCB sulfone 2i had 13minute half-life ( 13 C NMR d 12.4 ppm), which demonstrated good agreement with the correlation. BCB-sulfoximines with adjustable N-functionality provided a tuneable and a much broader range of strain-release reactivity and without reliance on modification of the arene. Figure 2. Strain release reactivity with different nitrogen protecting groups.