1.1: 83 percent / aq. HCl / tetrahydrofuran / 11 h / 20 °C 2.1: 95 percent / 3-ethyl-5-(2-hydroxyethyl)-4-methyl thiazolium bromide; DBU / 2-methyl-propan-2-ol / 0.5 h / 40 °C 3.1: H2 / Pd/C / toluene / 1.5 h / 20 °C 3.2: 75 percent / air / toluene / 5 h / 110 °C 4.1: 86 percent / aq. H2SO4 / dioxane; methanol / 96 h / 20 °C View Scheme