SUSTAINABLE TWO-PHASE BROMINATION OF TOLUENE WITHH₂O₂/KBr CATALYZED BY MO(VI) AND V(V)

Years ago, inspired by the mode of action of V-dependent haloperoxidases enzymes, we developed a synthetic procedure for the bromination of organic substrates in a two-phase system (H₂O/CHCl₃).^1,2 Excellent results in terms of yields and selectivities were obtained, both with V(V) and Mo(VI) catalysts, with different substrates: aromatics, alkenes and alkynes.³ Subsequently the chlorinated phase was substituted with Ionic Liquids obtaining an even more performing procedure in particular with double and triple bonds.^3,4

Recently, we have applied our procedure to the bromination of toluene.

Substrate consumption and products formation in the V-catalyzed bromination of Toluene with H₂O₂/KBr in a two-phase system (H₂O/CH₂Cl₂) at r.t.

The reaction proceeds under very mild conditions, and interestingly the substrate can be used also in the absence of any other solvent. Products distribution fluctuates as function of experimental conditions, always being the a-bromotoluene the major product. Comparison of the catalytic activity of the two catalysts in the title reaction has been carried out.

Preliminary mechanistic studies have been also performed and will be discussed.

1. V. Conte, F. Di Furia, S. Moro, Tetrahedron Lett., 35, 1994,7429-7432.

2. M. Andersson,V. Conte, F. Di Furia, S. Moro, Tetrahedron Lett., 37, 1996, 8609-8612.

2. V. Conte, B. Floris, Inorg. Chim. Acta, 363, 2010, 1935-1946.

3. V. Conte, B. Floris, P. Galloni, A. Silvagni, Adv. Synth. Catal., 347, 2005, 1341-1344.