Facile, efficient, and environmentally friendly α- and aromatic regioselective chlorination of toluene using KHSO5 and KCl under catalyst-free conditionsElectronic supplementary information (ESI) available. See DOI: 10.1039/c5nj00118h

Toluene was subjected to room-temperature chlorination with the KHSO 5 -KCl system in organic solvent-water mixtures. In a typical reaction, the amounts of toluene, KHSO 5 , and KCl were 1.0, 5.0 and 7.5 millimoles, respectively. The reaction mixtures, consisting of an organic solvent (2.50 mL) and water (1.50 mL), were rather multiphase like slurry. Depending on the nature of the organic solvent present in the solvent mixtures, either α-chlorination or aromatic chlorination of toluene was favoured. The chlorinated solvents CH 2 Cl 2 , CHCl 3 , and CCl 4 favoured the α-chlorination, yielding >81% benzyl chloride selectivity in 38-59% toluene conversions in 1 hour. The water miscible polar solvents C 2 H 5 OH, CH 3 OH, and CH 3 CN favoured the aromatic chlorination, yielding 61-86% chlorotoluene selectivity in >98% toluene conversions in 1 hour. Reactions carried out in all solvent mixtures yielded only chlorinated toluene products. The method presented here for the regioselective chlorination of toluene meets the goals of green chemistry as well in a number of ways: (a) catalyst-free conditions; (b) nontoxic, green, safe, stable, and inexpensive reagents; (c) low environmental impact; (d) no heating or cooling; (e) simple and cheap operation; and (f) high regioselectivity. The nontoxic, green, safe, stable, and inexpensive reagents Oxone and KCl were employed in the non-catalyzed chlorination of toluene at room temperature.