Eosin Y-Catalyzed Visible-Light-Mediated Aerobic Transformation of Pyrazolidine-3-One Derivatives

Abstract

By utilizing an underexplored reactivity of N1-substituted pyrazolidine-3-ones, we developed a visible-light-induced aerobic oxidation of N1-substituted pyrazolidine-3-one derivatives yielding the corresponding azomethine imines. The resulting azomethine imines can be further reacted with ynones in situ under copper catalyzed [3 + 2] cycloaddition reaction conditions yielding the corresponding pyrazolo[1,2-a]pyrazoles in good yields. The methodology can be extended to other 1-aryl-substituted pyrazolidinones which undergo endocyclic oxidation deriving the corresponding pyrazolones as single products.

Synthesis of 6,7-Dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles by Azomethine Imine-Alkyne Cycloadditions Using Immobilized Cu(II)-Catalysts

“…Active methylene compounds 1a – g , 3-aminopropyl silica gel ( 3 ) (for preparative chromatography, 40–63 µm, 0.9 mmol/g amino groups, pore size ~9 nm), 4-aminobenzoic acid ( 12 ), Cu(OAc) 2 ·H 2 O, N,N -dimethylformamide dimethylacetal (DMFDMA, for synthesis, ≥96%), tert -butoxy-bis(dimethylamino)methane (TBDMAM, technical grade), and 1,1′-carbonyldiimidazole (CDI) are commercially available (Sigma-Aldrich). Enaminones 2a [ 72 ], 2b [ 73 ], 2c [ 74 ], 2d [ 75 ], 2e [ 76 ], 2f [ 77 ], and 2g [ 78 ], bis-enaminones 9a , 9b [ 70 ], and 9c [ 71 ], and azomethine imines 6a , f [ 79 ], 6b , e [ 80 ], 6c [ 81 ], and 6d [ 82 ] were prepared following the literature procedures.…”

Eosin Y mediated photo-catalytic C–H functionalization: C–C and C–S bond formation

“…This strategy also worked smoothly for both electron-donating and -withdrawing groups and gave the final products in excellent yields (Scheme 53). 52…”

“…This strategy also worked smoothly for both electron-donating and -withdrawing groups and gave the final products in excellent yields (Scheme 53). 52 Recently the Yu group synthesized C-alkynyl glycosides via eosin-mediated photoinduced catalyzed reductive coupling between glycosyl bromides (117) and alkynyl bromides (118).…”

Photoinduced Ring Opening of Methyl 1-Aryl-5-oxo-6,7-dihydro-1H,5H-pyrazolo[1,2-a]pyrazole-2-carboxylates in the Presence of Diaryl Disulfides

“…Numerous methodologies for the synthesis and derivatization of pyrazoles have been reported and they continue to be developed [7]. For instance, we recently disclosed a photoredox-catalyzed oxidation of N1-substituted pyrazolidin-3-ones to azomethine imines [8], as well as the photoinduced selective preparation of highly functionalized pyrazoles from pyrazolo[1,2-a]pyrazolones (Scheme 1) [9]. In this study, we focused on the C7-N8 homolytic bond cleavage of pyrazolo [1,2-a]pyrazolones, which occurs upon the irradiation of the substrates with a 400 nm light source.…”