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Synthesis of N-neterocycles via intramolecular reductive cyclizations of nitroalkenes
(2007) Merisor, Elena; Beifuss, Uwe
The current work describes a new triethyl phosphite mediated domino reaction of ω-nitro-alkenes which in one step cyclize to the corresponding saturated N-heterocycles. The one-step domino reaction described in this work includes a three-step reaction, a nitroso-ene reaction being coupled with two reduction reactions. A new C-N bond is formed and saturated N-heterocycles are synthesized. The microwave irradiation of the ω-nitroalkenes has been developed as an alternative protocol, having the advantage that the formation of byproducts can be suppressed and the reaction times reduced. The reductive cyclization reaction mediated by triethyl phosphite allows preparation of a series of saturated N-heterocycles such as substituted 3,4-dihydro-2H-1,4-benzoxazines, 1,2,3,4-tetrahydroquinoxalines and 1,2,3,4-tetrahydroquinolines. The newly developed domino reaction can also occur under CO pressure using metal catalysts, allowing the formation of saturated N-heterocycles. Since the reductive cyclizations reported in this work are transition metal-catalyzed domino processes without precedent, they could be of significant interest to the field of synthetic chemistry and ?Life Sciences?.