Fig. 2: Scope of application of the superacid-mediated Friedel–Crafts methylation.

Overall yield and regioselectivity determined by NMR or HPLC analysis of the crude product (isolated yield of pure major regioisomer in parenthesis). Reaction conditions: arene (1 equiv.), Me₂SO₄ (1 equiv.), HF/SbF₅ (v/v = 1/1), 0 °C, 4 h. ^a After 2 h. ^b Using Me₃PO₄ (0.37 equiv.). ^c At room temperature. ^d After 16 h. ^e Using Me₃PO₄ (1 equiv.). ^f Isolated as mixture of regioisomers (calculated yield of major regioisomer in parenthesis). ^g Yield of major regioisomer only; estimated by HPLC analysis of the crude product (isolated yield in parenthesis). ^h Using (CD₃)₂SO₄ (1 equiv.). ⁱ Using (¹³CH₃)₂SO₄ (1 equiv.).