Synthesis of Densely Substituted Sulfonylfurans and Dihydrofurans via Cascade Reactions of α‑Functionalized Nitroalkenes with β‑Ketosulfones

The reaction of β-ketosulfones with different α-functionalized nitroalkenes affords diversely substituted sulfonylfurans and dihydrofurans. Furthermore, β-ketosulfones react with α-bromonitroalkenes and α-hydrazinonitroalkenes via a cascade Michael addition-cyclization protocol to afford nitrodihydrofurans and hydrazinodihydrofurans, respectively, bearing a key sulfonyl group, in excellent yields with a broad substrate scope. Application of these products has been demonstrated by the synthesis of pyrroles and pyrazoles in good yields. The reaction of β-ketosulfones with nitroallylic acetates yields tetrasubstituted sulfonyl furans through a cascade SN2′-intramolecular Michael reaction, followed by aromatization. The gram-scale synthesis of a representative example of sulfonylfurans was carried out to demonstrate the synthetic efficiency of the methodology.β-酮砜（β-ketosulfones）与不同α-官能化硝基烯烃（α-functionalized nitroalkenes）发生反应，可得到多种取代的磺酰基呋喃（sulfonylfurans）与二氢呋喃（dihydrofurans）。此外，β-酮砜可通过迈克尔加成-环化级联反应策略，分别与α-溴代硝基烯烃（α-bromonitroalkenes）和α-肼基硝基烯烃（α-hydrazinonitroalkenes）反应，得到带有关键磺酰基团的硝基二氢呋喃（nitrodihydrofurans）与肼基二氢呋喃（hydrazinodihydrofurans），该方法产率优异且底物适用范围广泛。通过以良好产率合成吡咯（pyrroles）与吡唑（pyrazoles），验证了上述产物的应用价值。β-酮砜与硝基烯丙基乙酸酯（nitroallylic acetates）发生反应，通过SN2'-分子内迈克尔加成级联反应并随后芳构化，得到四取代磺酰基呋喃。通过克级规模合成一例代表性磺酰基呋喃产物，验证了该合成方法的高效性。