Organic Dye-Photocatalyzed Acylnitroso Ene Reaction

Rose bengal, an inexpensive and readily available organic dye, is demonstrated to be a photoredox catalyst for the formation of transient acylnitroso intermediates under visible light irradiation. This method is operationally simple and uses air as the terminal oxidant. Reactions of acylnitroso with a range of functionalized alkenes give intermolecular acylnitroso ene products in moderate to good yields. This is an environmentally friendly allylic amination methodology that avoids the use of metal catalysts and stoichiometric amount of oxidants. A plausible reaction mechanism is proposed on the basis of singlet oxygen and fluorescence quenching studies.