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

Abstract

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 S N 2′-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.

Recent Advances for the Synthesis of N‐Unsubstituted Pyrroles

“…Group of Sampak Samanta have investigated a new method for the synthesis of fused‐dihydropyrroles by the selective cyclization of N ‐sulfonyl ketimines with ethenesulfonyl fluorides [112] . The pharmacologically important 2‐pyrrolyl phenol 367 could be prepared separately from 363 or 364 by desulfonylation process (method A or B) with high yields (81‐90 %).…”

“…Group of Sampak Samanta have investigated a new method for the synthesis of fused-dihydropyrroles by the selective cyclization of N-sulfonyl ketimines with ethenesulfonyl fluorides. [112] The pharmacologically important 2-pyrrolyl phenol 367 could be prepared separately from 363 or 364 by desulfonylation process (method A or B) with high yields (81-90 %). On the other hand, the direct synthesis of 2-pyrrolyl phenol was performed via a sequential reaction of 365 with ChemistrySelect 366 in DMSO using DBU in 58 % yield, followed by the addition of potassium tert-butoxide (method C) (Scheme 122).…”

A Molecular Iodine-Mediated Synthesis of Cyclopenta[c]furo[3,2-b]furan-5,6-diones: Assembly of an Angular Dioxatriquinane Core

“…Bromonitrostyrenes are useful reagents in the synthesis of heterocyclic compounds . The bromo and nitro groups in β-bromo-β-nitrostyrenes can behave as good leaving groups in nucleophilic substitution reactions in comparison with bromoalkenes or nitroalkenes. − …”

DBU Promoted Polysubstituted Arene Formation via a Michael Addition/Cyclization/Elimination Cascade Reaction

“…Recently, the easily accessible α-brominated and chlorinated nitrostyrenes 1 and 2 [ 13 , 14 ] were emerged as powerful C 2 synthons in the synthesis of different ring systems ( Figure 1 a). In particular, with the utilization of different C 3 synthons, a series of polysubstituted heteroarenes were constructed through (3 + 2) cyclization process, including furans [ 15 , 16 , 17 , 18 ], pyrazoles [ 19 , 20 , 21 ], imidazoles [ 22 ], triazoles [ 23 , 24 , 25 ], and pyrroles [ 26 , 27 , 28 , 29 , 30 ]. The versatilities of nitrostyrenes 1-2 were based on the electron deficiency of the double bound and the high reactivity of the leaving group X (X= Cl, Br) [ 31 , 32 , 33 ].…”