In an embodiment, a method of producing a bisphenol comprises reacting a phenolic compound with a reactant comprising one or both of an aldehyde and a ketone in the presence of a catalyst system and methanol to produce the bisphenol; wherein the methanol is present in an amount of 250 to 5,000 ppm based on the total weight of the reactant; wherein the catalyst system comprises an ion-exchange resin comprising a plurality of sulfonic acid sites; and 5 to 35 mol % of an attached promoter molecule based on the total moles of the sulfonic acid sites in the catalyst system; and wherein the attached promoter molecule comprises at least two thiol groups per attached promoter molecule.