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Experimental protocols to obtain compounds 4a–d and 5a–d. Reagents and reaction conditions: (a) cold concentrated sulfuric acid as a solvent, equimolar amount of sulfonitric mixture, T = −10 °C, magnetic stirring, 15 min; (b) anhydrous dichloromethane as a solvent, AlCl3 (30 mmoles excess), ice-salt bath; magnetic stirring, r.t., overnight; quenching with a cold 5% H2SO4 solution.
