Synthesis of Spiro[pyrazolin-3,3′-oxindoles] and 3-Arylcarbonylmethyl Substituted Ylideneoxindoles by 1,3-Dipolar Cycloadditions of 3-Ylideneoxindoles and In-Situ-Generated α-Diazoketones

Al-Hussain S, E. A. Zaki M, H. Asghar B, A. Muhammad Z. Synthesis of spiropyrazoles under organic and nonorganic catalysis

Abstract:

Spiropyrazoles display many biological biological activities such as antitumor, vasodilation, analgesic, phosphodiesterase inhibitors, aldosterone antagonistic, anabolic, androgenic, anti-inflammatory, progestational and salt-retaining activities and they also exert neuroprotection in dopaminergic cell death. Many efforts have been made to obtain these derivatives with high yield and excellent regio-, diastereo- and enantioselectivities. Most of the spiroprazole synthesis methods were proceeded in good to excellent yield in the presence of organic catalysts as for examples squaramide, NHC pre-catalyst, pyrrole derivatives, bis-oxazoline, DMAP, DABCO, thiourea derivatives, DBU, acetic acid and quinoline catalysts. In addition, the inorganic and organo-metallic catalysts have been proven their efficiency in synthesis of various types of spiro-pyrazoles in excellent yield. Thus, in this review we have compiled all citations for the synthesis of spiropyrazoles in the presence of various types of catalysts such as organic, inorganic, and metalorganic catalysts in the range 2020 to 2012. This review article is a useful compilation for researchers interested in the synthesis of spiropyrazole derivatives and will assist them in selecting appropriate catalysts for preparation of their spiropyrazoles.

Diastereoselective trans Cyclopropanation of 3-Alkylidene Oxindoles with In Situ Generated α-Diazo Carbonyls or α,β-Unsaturated Diazo Compounds

An efficient diastereoselective trans cyclopropanation of 3-alkylidene oxindoles with in situ generated α-diazo carbonyl compounds or α,β-unsaturated diazo compounds under metal-free conditions has been developed to synthesize 3-spirocyclopropyl-2-oxindole derivatives. The procedure is based on the 1,3-dipolar character of the corresponding diazo compounds under base-catalyzed conditions. The method has a wide substrate scope and uses easily available starting materials.

Synthesis of spiro-4H-pyrazole-oxindoles and fused 1H-pyrazoles via divergent, thermally induced tandem cyclization/migration of alkyne-tethered diazo compounds

A thermally induced, substrate-dependent reaction of alkynyl diazo compounds has been developed. This transformation produces spiro-4H-pyrazole-oxindoles and fused 1H-pyrazoles in good to high yields from the corresponding alpha-cyano and alpha-sulfonyl diazo compounds. The salient features of this reaction include excellent chemoselectivity and atom-economy, mild reaction conditions, simple purification and potential for large scale production.

Solvent-Controlled, Tunable Domino Reaction of 3-Ylideneoxindoles with in Situ-Generated α-Aryldiazomethanes: A Facile Access to 3-Spirocyclopropyl-2-oxindole and Pyrazoloquinazolinone Scaffolds

A mild and efficient solvent-controlled, metal-free switchable 1,3-dipolar cycloaddition/ring contraction or ring expansion domino reaction of 3-ylideneoxindoles with in situ-generated α-aryldiazomethanes has been developed. This domino reaction provided a series of aryl-substituted 3-spirocyclopropyl-2-oxindoles and pyrazoloquinazolinones with excellent regio- and diastereoselectivity from common substrates under varying solvent conditions.

NHC-catalyzed [4+2] cycloaddition reactions for the synthesis of 3′-spirocyclic oxindoles via a C–F bond cleavage protocol

A chiral NHC-catalyzed cycloaddition of γ-fluoroenals is developed. The nucleophilic γ-carbon generated via C–F bond cleavage undergoes highly enantioselective cycloaddition (up to >99% ee) to isatins and provides 3′-spirocyclic oxindoles in good yields (up to 91%).

Bromide-catalyzed electrochemical trifluoromethylation/cyclization of N-arylacrylamides with low catalyst loading

An electro-generated trifluoromethyl radical mediated by a bromide ion is efficiently applied to the trifluoromethylarylation/cyclization of N-arylacrylamides.