“…19 The coupling occurred effectively at 80°C in the presence of p-toluenesulfonic acid, and regeneration of the palladium(II) catalyst by potassium persulfate or benzoquinone, the former being used to establish the scope of the procedure because of its lower Ph Ph Ph Ph R 1 = R 2 = R 3 = R 4 = H (17%); R 1 = R 4 = Me, R 2 = R 3 = H (60%) R 1 = R 4 = Et, R 2 = R 3 = H (35%); R 1 = n-Bu, R 2 = R 3 = H, R 4 = Me (27%) R 1 = R 3 = Me, R 3 = R 4 = H (43%); R 1 = R 2 = R 3 = Me, R 4 = H (52%) R 1 = R 2 = R 4 = Me, R 3 = H (50%); R 1 = R 4 = Me, R 2 = Cl, R 3 = H (16%) R 1 = OMe, R 2 = R 4 = Me, R 3 = H (47%); R 1 = R 3 = Me, R 2 = OMe, R 3 = H (52%) (excess)…”