Transition Metal-Free De Novo Synthesis of Sulfonated Pyrazoles from Sulfonyl Hydrazides, 1,3-Diketones, and Sodium Sulfinates at Room Temperature

Abstract

A transition metal-free method for de novo construction of diverse sulfonated pyrazoles from readily available sulfonyl hydrazides, 1,3-diketones, and sodium sulfinates was established under mild conditions. Pyrazoles bearing two different sulfonyl groups were obtained in one step. The method features a diversity of substituents of the pyrazole products and a remarkably simple work-up.

Electrochemical Synthesis of Polysubstituted Sulfonated Pyrazoles via Cascade Intermolecular Condensation, Radical–Radical Cross Coupling Sulfonylation, and Pyrazole Annulation

“…Cyclic voltammograms were recorded on a CHI 660E potentiostat. Compounds 3a – 3b , 3d , 3f – 3g , 3m – 3n , 3r – 3t , 3v , 3x – 3zc , 5a , 5c – 5n , 5p – 5r , 8 , 9 , 10 , 12 , 13 , 17 , 18 , 20 , and 21 are known, and their spectroscopic features are in good agreement with those reported in the literature.…”

“…However, the use of stoichiometric amounts of exogenous additives/oxidants and the scope of sulfonyl hydrazide have also limited the applicability of these methods. Moreover, Ma et al developed a molecular iodine-promoted three-component reaction for the synthesis of fully substituted sulfonated pyrazoles from sulfonyl hydrazides, 1,3-diketones, and sodium sulfonates using K 2 HPO 4 ·3H 2 O as an additive, sulfonyl hydrazides as the ring component, and sodium sulfonates as the sulfonyl precursor . In addition, in recent years, novel and efficient methods for the synthesis of various polysubstituted pyrazoles have been intensively developed .…”

Facile One-Pot Preparation of 5-Substituted 4-Iodo-1-tosylpyrazoles from N-Propargyl-N′-tosylhydrazines through Iodocyclization

“…1 and 2). Recent examples of pyrazoles prepared in the absence of transition metals are as follows: 4 1-aryl-4-iodopyrazoles­ from the reaction of N -aryl- N ′-(α-alkynyl)­hydrazones with molecular iodine (I 2 ) and NaHCO 3 ; 4a 3-substituted pyrazoles from the reaction of propargylamines with m CPBA and then with hydrazines; 4b 3,5-disubstituted 1-arylpyrazoles from the reaction of α,β-unsaturated aldehydes with arylhydrazines and I 2 ; 4c 1-arylpyrazole-4-carboxylate esters from the reaction of α-[( tert -butoxycarbonyl)oxy]methylacrylate esters with N -arylazosulfones and Bu 3 P; 4d 5-amino-3-aryl-1-tosylpyrazoles from the reaction of N -tosylhydrazones with isocyanides, t BuOOH, and I 2 ; 4e ethyl 1-aryl-5-(acetylmethyl)pyrazole-4-carboxylates from the reaction of ethyl acetoacetate with arylhydrazines and NaOEt; 4f 1-aryl-5-hydroxy-4-thioarylpyrazoles from the reaction of arylhydrazines with ethyl acetoacetate, arenethiols, and I 2 ; 4g 1,5-diaryl-4-iodo-3-(trifluoromethyl)pyrazoles from the reaction of N -arylhydrazones of arylethynyl trifluoromethyl ketones with I 2 ; 4h 1,4-bis(arenesulfonyl)pyrazoles from the reaction of β-amino-α,β-unsaturated ketones­ with arenesulfonylhydrazines, t BuOOH, and I 2 ; 4i 5-amino-1-arylpyrazoles from the reaction of 3-aminocrotonitrile with arylhydrazine and 1 M HCl under microwave irradiation; 4j 1,3-diarylpyrazoles from the reaction of hydrazonyl chlorides with benzyl vinyl ether and Et 3 N; 4k 1,3-di­aryl-5-(bromomethyl)pyrazoles from the reaction of hydrazonyl chlorides with dimethyl propargylsulfonium and K 2 CO 3 ; 4l 1,4-bis(arenesulfonyl)pyrazoles from the reaction of 1,3-diketones with arenesulfonylhydrazines, arenesulfinate salts, and I 2 ; 4m and 1-aryl-4-selenoarylpyrazoles from the reaction of 1,3-diketones with arylhydrazines and diaryl diselenides by electrochemical method. 4n Examples of pyrazoles prepared in the presence of transition metals are as follows: 5 1-benzylpyrazole-4-carboxylates from the reaction of 2,3-allenoates with benzylamine in the presence of Cu(OAc) 2 ; 5a 1,4-diarylpyrazoles from the reaction of N -arylsydnone with terminal alkynes in the presence of silica-supported Cu(OAc) 2 ; 5b 1,5-diaryl-3-(trifluoromethyl)pyrazoles from the reaction of alkynyl trifluoromethyl ketones and arylhydrazines in the presence of AgOTf; 5c 1-aryl-3,5-dimethylpyrazoles from the reaction of arylhydrazines with Cu(acac) 2 under microwave irradiation; 5d 1,3,5-triaryl-4-selenophenylpyrazoles from the reaction of chalcones with arylhydrazines in the presence of CuBr; 5e 1-tosyl­pyrazole-4-boronate esters from the reaction of N -tosyl-(α-alkynyl)hydrazones with B -chlo...…”

Iodine‐Promoted Tandem Pyrazole Annulation and C−H Sulfenylation for the Synthesis of C4‐Sulfenylated Pyrazoles

“…al established the preparation of diverse sulfonated pyrazoles bearing two different sulfonyl groups from sulfonyl hydrazides, 1,3-diketones, and sodium sulfinates (Scheme 1g). [18] Lee et.al synthesized 3,5-dimethyl-4-(phenylthio)-1H-pyrazole by a two-step reaction. Namely, the reaction of 3-chloro-2,4-pentanedione and benzenethiol in the presence of piperidine to form 3-(phenylthio)pentane-2,4-dione, followed by the cyclization with hydrazine hydrate to yield pyrazole thioether derivatives (Scheme 1h).…”

“…Similarly, Ma et. al established the preparation of diverse sulfonated pyrazoles bearing two different sulfonyl groups from sulfonyl hydrazides, 1,3‐diketones, and sodium sulfinates (Scheme 1g) [18] . Lee et.al synthesized 3,5‐dimethyl‐4‐(phenylthio)‐1 H ‐pyrazole by a two‐step reaction.…”