Cu(acac)₂ Immobilized in Ionic Liquids: A Novel and Recyclable Catalytic ­System for Aziridination of Olefins Using PhI=NTs as Nitrene Donor

Abstract

Copper(II) acetylacetonate immobilized in ionic liquids efficiently catalyzes aziridination of olefins in good yields at a ­faster rate than the earlier reported methods using PhI=NTs as a ­nitrene donor with easy catalyst/solvent recycling.

copper acetylacetonate - ionic liquids - aziridination - olefins - PhI=NTs

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Typical Experimental Procedure: Cu(acac)₂ (0.010 g, 7.7 mol%), styrene (0.56 ml, 5 mmol) and PhI=NTs (0.372 g, 1 mmol) were added to the ionic liquid (1 mL) and the reaction mixture was stirred at r.t. for 25 min. The reaction was monitored by the disappearance of PhI=NTs. After completion of the reaction, the product was extracted with Et₂O (3 × 4 mL) by simple decantation and purified by column chromatography on silica gel with petroleum ether and EtOAc (95:5) as eluent. The ionic liquid containing Cu(acac)₂ was dried under vacuum for the next run. The resulting products were analyzed by NMR. Yield: 0.240 g, 88%. ¹H NMR (400 MHz, CDCl₃): δ = 7.86 (d, J = 8.3 Hz, 2 H, Ar-H), 7.27 (m, 7 H, Ar-H), 3.77 (dd, J _cis = 7.2 Hz,
J _trans = 4.5 Hz, 1 H, CHPh), 2.98 (d, J = 7.8 Hz, 1 H, cis-CH-aziridine) 2.43 (s, 3 H, Ar-Me), 2.38 (d, J = 4.4 Hz, 1 H, trans-CH-aziridine).