Application of the crystal violet indicator to for any decomposition of common dioxaborolanes, HBpin and HBcat, was next explored. A control (background) reaction was performed to verify crystal violet 1 did not react directly with HBpin or HBcat (Figure ). Addition of HBpin or HBcat (6 mM in toluene or neat) to the crystal violent solution resulted in no colour change. This control can also be used as a quality check for dioxaborolanes; as dioxaborloanes, HBpin and HBcat, disproportionate on standing to B2pin3 and B2cat3, respectively, and BH3 (see Supporting Information, Scheme S1). Any reagent decomposition was confirmed and visualised using the crystal violet test; the BH3 impurity causing a colour change of the indicator solution (see Supporting Information, S3.5). This serves as a rapid quality test for these reagents so ensuring high purity and avoiding potential false positive results.