Mono- and dinitration of pentafluorosulfanylbenzenes with [NO2][BF4], and substrate selectivity (PhSF5 vs PhCF3 and PhSF5 vs PhNO2) in competitive nitration

PhSF5 1 reacts with NO2+BF4−/TfOH in CH2Cl2 (DCM) at room temperature to give 1-nitro-3-(pentafluorosulfanyl)benzene 2 in near quantitative yield. The dinitro derivative 4 is synthesized from 2 by reaction with NO2+BF4−/TfOH at 70 °C. The p-MeC6H4SF5 is mononitrated at room temperature with NO2+BF4−/DCM and dinitrated with NO2+BF4−/TfOH. Substrate selectivity ( k PhSF 5 / k RPh ) in competitive nitration for PhSF5/PhCF3 and PhSF5/PhNO2 with NO2+BF4− in DCM at room temperature was determined at 21.3 and ∼1 respectively. Relative stability of the corresponding benzenium ions were gauged by DFT from the isodesmic proton transfer reaction SF5–C6H6+ + R-C6H5 → SF5–C6H5 + R-C6H6+ (R = CF3 and NO2). These studies indicate that reactivity of ArSF5 in SEAr is similar to ArNO2.