In summary, we have discovered 1) that triethylamine sulfur trioxide complex, is in fact a triethylsulfoammonium betaine (TESAB) reagent based on single crystal X-ray crystallography data analysis. And 2) that TESAB can find use as an all-in-one Parikh-Doering oxidation reagent that incorporates both the key sulfuryl activating group for DMSO and releases an N(sp 3 ) base that deprotonates the alkoxydimethylsulfonium intermediate facilitating the first example of a no-additional base required Parikh-Doering reaction.