Asymmetric α-Aminoxylations of Stoichiometric Ketones Using 2-Nitrosotoluene

Abstract

Asymmetric aminoxylations of a stoichiometric amount of ketones were accomplished through O-nitrosoaldol reactions of 2-nitrosotoluene catalyzed by a proline-based tetrazole. The advantages of 2-nitrosotoluene and the tetrazole over nitrosobenzene and proline, respectively, were demonstrated.

Key words

aminoxylations - O-nitrosoaldol reactions - α-aminoxy cyclic ketones - proline-based tetrazole - nitrosotoluene

References and Notes

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10

Typical Experimental Procedure
2-Nitrosotoluene (1.0 mmol, 121 mg) in DMF (1 mL) was added over 3 h via syringe pump to a solution of the tetrazole catalyst (0.1 mmol, 14 mg) and the cyclic ketone (1.0 mmol) in DMF (1 mL) cooled to 0 ˚C. After completion of the addition, the mixture was stirred at 0 ˚C for a further 5 h. Saturated aq NHCl₄ was added and the mixture extracted with AcOEt. The crude product was chromatographed on silica gel to give a mixture of the mono- and bisamin-oxylation products.

11

2-Isopropylnitrosobenzene was prepared in high purity by oxidation of 2-isopropylaniline with Oxone in H₂O at 0 ˚C.