Inter- and Intra-Molecular Organocatalysis of S2 Fluorination by Crown Ether: Kinetics and Quantum Chemical Analysis.

We present the intra- and inter-molecular organocatalysis of S2 fluorination using CsF by crown ether to estimate the efficacy of the promoter and to elucidate the reaction mechanism. The yields of intramolecular S2 fluorination of the veratrole substrates are measured to be very small (<1% in 12 h) in the absence of crown ether promoters, whereas the S2 fluorination of the substrate possessing a crown ether unit proceeds to near completion (~99%) in 12 h. We also studied the efficacy of intermolecular rate acceleration by an independent promoter 18-crown-6 for comparison.