Un-catalyzed tandem Knoevenagel–Michael reaction for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) in aqueous medium

1,3,5-Tris(hydrogensulfato) Benzene: A New and Efficient Catalyst for Synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol) Derivatives

“…Recently, several different three component one-pot condensation reactions have been reported between 1-phenyl-3-methylpyrazol-5-one and a variety of different aldehydes for the construction of 4,4'-(arylmethylene)bis(1H-pyrazol-5-ol) derivatives [6, 20−32]. Several different catalysts have been reported to promote this reaction, including ceric ammonium nitrate (CAN) [6], sodium dodecyl sulfate (SDS) as a surfactant catalyst [20], ETBA [21], NaBr [22], [Cu(3,4-tmtppa)](MeSO 4 ) 4 [23], silica-bonded S-sulfonic acid (SBSSA) [24], silica sulfuric acid (SSA) [25], H 2 O [26], sulfuric acid ([3-(3-silicapropyl)sulfanyl] propyl)ester (SASPSPE) [27], xanthan sulfuric acid [28], PEG-SO3H [29], ionic liquid [HMIM]HSO4 [30], 3-minopropylated silica gel (AP-SiO2) [31], and phosphomolybdic acid [32].…”

An efficient and green one-pot three-component synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol)s catalyzed by 2-hydroxy ethylammonium propionate

“…The condensation of aldehydes with two equivalents of 3-methyl-1-phenyl-5-pyrazolone is a known used route for synthesizing 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol)s. Xanthan sulfuric acid (4), phosphomolybdic acid (5), silica sulfuric acid (6), 3-aminopropylated silica gel (7), sodium dodecyl sulfate (8), tetramethyl-tetra-3,4-pyridinoporphyrazinato copper(II) methyl sulfate (9), poly(ethylene glycol)-bound sulfonic acid (10), cellulose sulfuric acid (11), lithium hydroxide monohydrate (12), 1,3,5-tris(hydrogensulfato) benzene (13), sulfuric acid ([3-(3-silicapropyl)sulfanyl]propyl)ester (14), ethylenediammonium diacetate (15), 2-hydroxy ethylammonium acetate (16), N-(3-silicapropyl)-N-methyl imidazolium hydrogen sulfate (17), benzyltriethylammonium chloride (18), ceric ammonium nitrate (19), silica-bonded S-sulfonic acid (20), 1,3-disulfonic acid imidazolium tetrachloroaluminate (21), and 1-sulfopyridinium chloride (22) can be used as catalysts for this transformation. Hasaninejad et al reported the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol)s by the condensation of aldehydes with two equivalents of 3-methyl-1-phenyl-5-pyrazolone in the absence of catalyst (23)(24)(25). Elinson et al applied the electrocatalytic procedure to this transformation (26).…”