Regioselectivity Control in Spirobifluorene Nitration under Mild Conditions: Explaining the Crivello's Reagent Mechanism

The regioselective nitration of 9,9′-spirobifluorene under mild conditions is reported for the first time by operating under Menke’s and Crivello’s conditions. The optimized protocol allows obtaining 2-nitro and 2,2′-dinitro-9,9′-spirobifluorene in yields of 79 and 95% and, for the first time, 2,2′,7-trinitro-9,9′-spirobifluorene with 66% yield. Besides, the role of dinitrate salt in Crivello’s protocol has been now clarified, which opens novel scenarios in the preparation of functional materials.