Structure Determinations of the Sulfonic Acid Monofluoromethylesters FSO2OCH2F and CF3SO2OCH2F in the Solid and Gaseous Phases
Final Report Abstract
The synthesis of superfluoromethyl (CF3SO3CH2F, SFM) and magic fluoromethyl (FSO3CH2F, MFM) is described. These are two easily synthesized, but highly effective and non-ozone depleting fluoromethylation reagents. They are analogous to the well-known and widely used methylation reagents CF3SO3CH3 and FSO3CH3. Both, superfluoromethyl, as well as magic fluoromethyl have been fully characterized by multinuclear NMR spectroscopy (1H, 13 C, 17 O, 19, 33S). Their structures have been determined in the solid state on in-situ grown crystals by X-ray diffraction and in the gas phase by electron diffraction. The results were compared with and supported by quantum chemical calculations. The structural properties of both compounds are quite similar. In the vapor, two conformations are present, while in the crystalline phase only the more stable conformer is detected. The O-CFH2 bond that is broken in the fluoromethylation reaction is 1.43 - 1.44 Å long in SFM and MFM and thus similar to the O-C bond length in the established fluoromethylating reagent fluoromethyl-2,4-6-trinitrophenylsulfonate (1.44 Å). The fluoromethylation efficiency of superfluoromethyl and magic fluoromethyl was demonstrated in a large number of fluoromethylation reactions. Fluoromethylation of various chalcogen compounds proceeded in a simple and clean manner. All fluoromethylated products were isolated as pure compounds and characterized by NMR, vibrational spectroscopy and single crystal X-ray diffraction. SFM and MFM were found to be highly reactive electrophilic fluoroalkylation reagents with superior properties including short reaction times, high yields, and easy handling work-up and removal due to their high volatility. They are therefore two new and powerful, non-ozone depleting, fluoromethylating reagents, ready for use in research and industry.
