Stereoselective synthesis of hydrazinodihydrofuransviacascade Michael addition–substitution involving the reaction of curcumin and other β-dicarbonyls with α-hydrazinonitroalkenes

Abstract

Reaction of 1,3-dicarbonyls with α-hydrazinonitroalkenes leads to 2-hydrazino-2,3-dihydrofurans with high stereoselectivity in the presence of a tert-leucine derived squaramide and K2CO3 in aqueous THF.

Squaramide Catalyzed Asymmetric Synthesis of Five‐ and Six‐Membered Rings

“…Namboothiri and co‐workers reported chiral squaramide Y and inorganic base assisted cascade reaction between cyclic 1,3‐dione 85 (cyclohexa‐1,3‐dione and dimedone) and α ‐hydrazino nitroalkenes 288 [118] . The reaction started with chiral catalyst Y promoted stereoselective Michael addition of the enolate form of 86 to hydrazino nitro alkenes to form chiral intermediate 290 .…”

“…Namboothiri and co-workers reported chiral squaramide Y and inorganic base assisted cascade reaction between cyclic 1,3-dione 85 (cyclohexa-1,3-dione and dimedone) and αhydrazino nitroalkenes 288. [118] The reaction started with chiral catalyst Y promoted stereoselective Michael addition of the enolate form of 86 to hydrazino nitro alkenes to form chiral intermediate 290. Subsequent elimination of nitro group generates hydrazonium intermediate 291 which undergoes intramolecular 5-exo-trig annulation promoted by K 2 CO 3 to deliver 2,3-disubstituted dihydrobenzofurans 289 as final products with moderate yields and enantioselectivities (Scheme 77).…”

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

“…21−29 These include O-heterocycles such as furans and pyrans 21 using 1,3-dicarbonyls/phenols; N-heterocycles such as pyrroles, 22 imidazoles, 23 imidazopyridines, 24 picolinate, 25 diazepines, 26 and indolizines 27 using 1,3-dicarbonyls, amidines, 2-aminopyridines, sulfamidate imines, thiourea, and 2-mercaptopyridne, respectively; S-heterocycles, for example, benzimidazothiazines 28 using 2-mercaptobenzimidazole; as well as other multiheteroatom-containing ones, for example, benzoxacinones 29 using 2-aminophenol. Similarly, reactions of α-hydrazinonitroalkenes with 1,3-binucleophiles such as phenols/naphthols 30 and 1,3-dicarbonyls 31 for the synthesis of (dihydro)furans, as well as with thioindoles for the synthesis of thienoindoles, 32 have been reported. The 1,2bielectrophilic reactivity of α-bromonitroalkenes with 1,3binucleophiles such as 1,3-dicarbonyls and amidines, respectively, has been exploited for the synthesis of dihydrofurans and imidazoles.…”

Enantioselective Desymmetrization of Curcumins with 3‐Olefinic Oxindoles for the Synthesis of Spirocyclohexanoneoxindoles

“…Synthesis of highly functionalized cyclohexanones and dihydrofurans via cascade double-Michael or Michael-intramolecular O-alkylation methods by treating curcumins with nitroalkenes [17][18][19][20] and chalcones [21] has been reported by us and others. Other reports on the reactivity of curcumins as Michael donors include a single Michael addition of curcumins to nitroalkenes under chiral tertiary amine-thiourea catalysis, [22] double-Michael addition of curcumins to 2-arylidene-1,3-indanediones in the presence of quinine for the enantioselective synthesis of spiroindanediones [23] and double-Michael addition of curcumins to oxindolylidene malononitrile for the synthesis of racemic spiro-oxindoles under DMAP catalysis (Scheme 1a).…”