The challenge in accessing 1-X is presumably due to the increased strain in the BN- [5]helicene relative to other azaborines. We hypothesised that a more reactive borylating electrophile would enable higher yielding access to 1-X. The exact electrophiles in established high temperature N-directed electrophilic C-H borylation reactions currently are ill-defined and may originate from the Lewis acid EX3 (EX3 = AlCl3 / BBr3) interacting with a B-X or N moiety of the aminoborane (Fig. ). Notably, reactions that proceed by accessing borenium cations by protonation of aminoboranes can lead to facile N-directed C-H borylation, even at 0 °C (Fig. ). This is consistent with N protonation of oxazaborolidines with HNTf2 forming more reactive (as catalysts in Diels-Alder reactions) Lewis acids than congeners derived from binding of BBr3 or AlCl3 at N. Thus conditions that form [ArylNH2BX2] + , [5-X] + , derived from 3-X or 4-X, partnered with a suitably weakly coordinating anion were sought to generate enhanced Ndirected C-H borylation. The simplest route to access [5-X] + is by protonation of an aminoborane by a sufficiently strong Brønsted acid. Bis(trifluoromethanesulfonyl)imide ([NTf2] -) was selected as the counterion as it is weakly coordinating (including towards borenium cations), and the strong Brønsted acid, HNTf2, is commercially available. Notably, the addition of HNTf2 to a range of aminoboranes led to no observable protonation, indicating an extremely low basicity of these aminoboranes. However, presumably some protonation is occurring as heating 3-X/HNTf2 mixtures at 85°C (a temperature at which dehydrohalogenation occurs to form the aminoborane 4-X) leads to formation of the azaborine 1-Br.