Increasing efficiency. An overarching goal of this line of research is to convert simple arenes into arynes. We partially achieved this goal by developing a two-step procedure to install a thianthrenium leaving group followed by ortho-deprotonation and -elimination (Scheme 1c). To further advance this goal, we re-evaluated this process to develop a one-pot procedure in which a simple arene can be selected from a chemical inventory and converted into a trapped aryne within several hours and without isolation of any intermediate species (Scheme 2). There were two major hurdles to merging the two-pot process into a onepot procedure: 1) two different solvents were used and 2) the acidic and basic conditions of the two steps are incompatible. We selected 4-chloroanisole 1a as the simple arene for study and the conditions presented below in entry 1 of Table are the result of a large number of experiments to rectify the challenges described above. Under these conditions 1a and TTO are dissolved in MeCN followed by the addition of triflic anhydride (Tf2O) at 0 °C to yield a homogenous light purple solution (Table ). After stirring for 30 minutes at room temperature, solid potassium phosphate is added to the vial, which results in a loss of the purple color and the reaction mixture is stirred for an additional five minutes. Furan 2a and solid sodium tertbutoxide are added to the vial and it is placed in a preheated (65 °C) aluminum block for 60 minutes. The trapped aryne product 3aa is observed in 86% 1 H-NMR yield from 1a; 3aa is obtained in 73% isolated yield after purification by column chromatography when the reaction is conducted on 0.5 mmol scale of 1a (Table ). A summary of experiments to demonstrate the relevance of each component in the reaction sequence is shown in Table (entries 2-8). Toluene was used in our prior work in the aryne forming step, however when the one-pot sequence is performed in toluene only trace (< 5%) amounts of 3aa were observed in the crude 1 H NMR spectrum (Table , entry 2). Triflic acid is a by-product of the C-H thianthrenation step and therefore leaving out the neutralization step (K3PO4) results in a greatly diminished yield of 3aa even with excess base in the second step (23%; Table , entry 3). Two other methods were tested to activate the TTO reagent under the one-pot conditions (Table , entries 4 and 5). The strongly acidic conditions involving a combination of TFAA and TfOH resulted in low yield (10%) of 3aa whereas conditions with the mixed anhydride TFAOTf resulted in comparable yield (83%) to those with Tf2O (Table , entries 4 and 5). The mixed anhydride TFAOTf, however, is substantially more expensive than Tf2O. Two other sulfonium salts were also tested as intermediates in this reaction (Table , entries 6 and 7). The tetrafluorinated analog of TTO, TFTO, resulted in low yield of 3aa (26%), though the dibenzothiophene analog, DBTO, resulted in a similar, but slightly lower, yield to that obtained with TTO (75%; a Conditions: 1a (0.1 mmol, 1 equiv.), TTO (0.1 mmol, 1 equiv.), Tf2O (0.12 mmol, 1.2 equiv.), MeCN (0.4 mL), 0 °C -r.t., 30 min; K3PO4 (0.1 mmol, 1 equiv.), r.t., 5 min; 2a (0.5 mmol, 5 equiv.), NaOt-Bu (0.2 mmol, 2 equiv.), 65 °C, 60 min.; yields determined by H NMR spectroscopic analysis of crude reaction mixtures with 1,3,5-trimethoxybenzene as internal standard. b Isolated yield on 0.5 mmol scale of 1a.