The SuFEx reaction mechanism proceeds via an S N 2 or additionelimination mechanism . To further distinguish concerted S N 2 and addition-elimination reaction paths, we computed the potential energy surfaces (PES) for the tandem reaction between benzofuran-3(2H)-ones 1a and β-phenylethenesulfonyl fluorides 2a (Scheme 1). on silica gel to give the desired product 3aa (White solid, 99%, 59.4 mg).