A solution of A1 (1 eq.) and Cs2CO3 (0.5 eq) in EtOH was stirred for 30 min at RT and then concentrated under reduced pressure. 2-Bromoacetophenone (1 eq.) was added to the resulting salt in DMF and the mixture was stirred for 1 h at RT under N2. The DMF was removed by azeotroping with xylene. EtOAc was added, the mixture was filtered and the residue was washed with EtOAc. The combined filtrates were concentrated under reduced pressure. A solution of the resulting oil and ammonium acetate (20 eq.) in xylene was heated at reflux (150° C. bath temperature) for 3 h. The mixture was cooled to RT, diluted with EtOAc and washed with water (×2), sat. aq. NaHCO3 solution and brine. The solution was dried (Na2SO4), concentrated under reduced pressure and the resulting brown oil was purified by chromatography on silica gel eluting with EtOAc/petrol ether (1.5:1) to obtain the imidazole A2 as a colourless oil. 1H NMR (300 MHz, CDCl3) δ: 10.50-9.60 (1H, m), 7.82-7.40 (2H, m), 7.38-7.29 (2H, m), 7.22-7.15 (2H, m), 5.13 (1H, br. s), 4.68-4.55 (1H, m), 2.39 (2H, t, J=7.2 Hz), 2.22-2.06 (4H, m), 1.99-1.80 (1H, m), 1.60-1.50 (2H, m), 1.43 (9H, s), 1.40-1.27 (4H, m). MS (ES) C22H31N3O3 requires: 385, found: 386 (M+H)+.
