Recent Advances in the Synthesis of Pyrazoles. A Review

Divergent Synthesis and Evaluation of Inhibitory Activities against Cyclooxygenases-1 and -2 of Natural Withasomnines and Analogues

“…Remaining two natural 1b and 1c could be prepared in good yields using 4-hydroxyphenyl-and 4-methoxyphenylboronic acids, respectively (entries 2, 3). Further applications to unnatural withasomnine analogues 1d-l were also demonstrated via the reaction between 16 and various arylboronic acids (entries [4][5][6][7][8][9][10][11][12]. The easy access to these analogues from the common intermediate 16 proved to be an advantage of our synthetic method compared to recent approaches by other research groups, 35,36) since all arylboronic acids appearing in Table 3 are commercially available.…”

“…[20][21][22] The isolation of withasomnines from Elytraria acaulis (Acanthaceae) 23) and Discopodium penninervium (Solanaceae) 24) was also reported in 2001 and 2008, respectively. Withasomnine 1a exhibited central nervous and circulatory system depressions, mild analgesic activity, 25,26) and TBL 4 , cyclooxygenase-1 (COX-1), and COX-2 inhibitory activities. 24) Because of these interesting biological activities, several reports of the synthesis of 1a were disclosed.…”

“…1,2) Of the many available methods for the synthesis of the pyrazole ring, the reaction of hydrazines with 1,3-dicarbonyl compounds is probably the most general and versatile. [3][4][5][6][7] In contrast, synthetic methods using the direct functionalization of pyrazoles have been little reported.…”

Recyclization of methyl 1-aryl-3-cinnamoyl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates in reaction with monosubstituted hydrazines

“…[1][2][3][4] The syntheses of pyrazoles have drawn considerable attention from organic chemists because of their diverse bioactivities. [5][6][7][8] Recyclization of 1H-pyrrole-2,3-diones by the action of monosubstituted hydrazines is a convenient method of synthesis of polyfunctional pyrazoles. These recyclization proceeds with the carbonyl group of acyl substituent at the С Compounds 3a-f are the colorless or light yellow crystals readily soluble in dimethylsulfoxide (DMSO) and dimethylformamide (DMF), hardly soluble in alcohols, ethers, chlorinated solvents, aromatics and insoluble in saturated hydrocarbons and water.…”

Silica gel-Supported Palladium Catalyst for the Acyl Sonogashira Reaction

“…By far the most common synthetic method for the preparation of substituted pyrazoles involves cyclocondensation of an appropriate hydrazine, which acts as a bidentate nucleophile, with other threecarbon units featuring two electrophilic carbons in a 1, 3-relationship. 25 Yet as shown earlier, an expedient, simple, and general method for the synthesis of pyrazoles is still being needed. Due to good activity of the Pd-SH-SILICA catalyst in acyl Sonogashira reaction, we further extended one-pot three component reactions.…”