Bidentate transient directing groups TDG1, and TDG8-TDG10 previously reported with Pd in C(sp 2 )-H functionalization were ineffective, as were monodentate aniline and benzylamine. Pleasingly, reactivity was observed when using anthranilic acid (TDG2), forming a presumed [5,6] cupracyclic intermediate, but related orthanilic acid was ineffective. More flexible b-alanine (TDG13) was more effective, giving 40% yield of 3a. Changing the acidic secondary binding site (P(O)(OH)2, SO3H, OH or OMe; TDG14-TDG17) gave lower yields, hence TDG13 was selected for further study. We next investigated reaction variables including copper sources, solvents, base, and other additives. CuF2 was the most effective copper source, and the yield could be further improved with carboxylate additives. Using 0.5 equiv of Cu(OAc)2 along with 1.5 equiv CuF2 was most effective. These copper sources both provide the necessary stoichiometric oxidant and effect the C-H functionalization. Further investigation confirmed K2CO3 and HFIP as the most effective base and solvent respectively. We observed that 25 mol% of the TDG was optimal, and both higher and lower loadings of b-alanine (5-100 mol%) resulted in lower yield of the sulfonyl aldehyde. A subsequent design of experiment (DoE) optimization focused on CuF2 equivalents, aldehyde equivalents and reaction concentration identified a key positive interaction between increasing equivalents of aldehyde and CuF2 (see supporting information for further details). Using a catalytic quantity of the TDG, the aldehyde in excess and 2 equiv of readily available CuF2, aldehyde 3a was isolated in 86% yield (Table , entry 1). Importantly, no reaction was observed in the absence of the TDG (Entry 2). Reduced reactivity was observed when either of the copper salts were omitted (Entries 3 and 4), and when no copper salts were present there was no observable reaction (Entry 5). Using only Cu(OAc)2 (2.5 equiv) in place of CuF2 remained effective but with reduced yield (Entry 6). A low yield of 3a was observed in the absence of K2CO3 (Entry 7). In the absence of the sulfinate salt, we observed the coupling of HFIP to give HFIP ether 4, whereby the solvent acts as a nucleophile in the reaction (Entry 8). We observed complete suppression of sulfone formation on addition of the radical trap TEMPO (Entry 9) indicating the potential for the involvement of radical species. The reaction was broadly tolerant to changes in concentration and increased temperature as assessed by the Glorius protocol, though sensitivity to increased water and oxygen was observed. With these optimized conditions we investigated the substrate scope with changes in sulfinate salt and aldehyde. A wide range of electronically and sterically diverse sulfinate salts were effectively coupled to give sulfones 3a-3m in good to excellent yields (Scheme 2a). Aryl sulfinate salts with electronically neutral (H) or electron donating (OMe, tBu) substituents were well tolerated (3b-3d). Sulfinate salts bearing arenes with inductively electron withdrawing groups (p-CF3, p-halides) were particularly effective giving yields of 63-74% without any unwanted cross coupling observed (3e-3h). More sterically encumbered orthosubstituted sulfinates such as 1-napthyl and o-tolyl derivatives gave sulfones 3i and 3j in 67% and 62% yield respectively. Methyl and cyclopropyl sulfinate salts were both effective in this oxidative coupling reacting in 77% and 76% yield respectively (3k and 3l). Additionally, bicyclo [1.1.1]pentane (BCP) sulfinate was used to introduce a BCP moiety which is increasingly of interest as a phenyl isostere. No obvious trend between the oxidation potential of the sulfinate salts and the yield of the coupling was observed, indicating direct oxidation of the salt to a sulfonyl radical may not be involved in the rate determining step of the reaction.