With the utility of the process demonstrated our attention turned to the mechanism. For this catalytic borylation a NacNacM-Y complex (e.g. including in catalytic processes). To further preclude the possibility of [(DMT)-BBN] + mediated borylation occurring in this process, the borylation of 2,5-N-trimethylpyrrole was attempted under the optimized aluminium-catalyzed conditions. This substrate was chosen as it undergoes C-H borylation using stoichiometric [(amine)-BBN] + in high yield at room temperature, while it has a sterically hindered borylation position located alpha to a methyl (C-H alumination is sensitive to steric environment). Under our optimized aluminium-catalyzed conditions < 5% C-H borylation of 2,5-N-trimethylpyrrole was observed at 100 ºC, further disfavoring a [(DMT)-BBN] + mediated catalytic borylation process (Scheme 2).