Synthetic Challenges in the Construction of 8- to 10-Membered Pyrazole-Fused Rings via Ring-Closing Metathesis

CuI-Catalyzed Coupling Reactions of 4-Iodopyrazoles and Alcohols: Application toward Withasomnine and Homologs

“…All reactions were Scheme 1. Versatile intermediate 4-allyloxy-1H-tritylpyrazole (4a), developed in our previous works (adapt from references [22][23][24][29][30][31]).…”

“…4-Allyloxy-1H-1-tritylpyrazole 4a (Scheme 1), derived from 4-iodopyrazole (1), played a key role as a versatile intermediate in our previous studies for the total synthesis of the pyrazole alkaloid, withasomnine (7) [22,23], and its six-membered homolog 11 [23][24][25][26][27], which were reported to exhibit COX-2 inhibitory activities [23,27,28]. Compound 4a was also extensively utilized as an important intermediate for the construction of new pyrazolefused heterobicyclic molecules 9 via ring-closing metathesis (RCM) (Scheme 1) [29][30][31]. However, the synthesis of compound 4a requires six steps from commercially available pyrazole, through 4-iodopyrazole (1), 4-iodo-1H-1-tritylpyrazole (2a), and aldehyde 3.…”

Novel family of bis-pyrazole coordination complexes as potent antibacterial and antifungal agents

“…More specically, pyrazole-based ligands have proven their efficiency for the construction of coordination complexes with useful applications in several elds not only in catalysis, 1 agricultural biotechnology, 2 corrosion inhibition, antimicrobial activity 3 and biology, 4 but also in pharmaceutical and medical research, 5 leading for instance to anti-inammatory 6,7 and anti-cancer agents. 8 According to recent literature reports, 9,10 the preparation of pyrazole based ligands with multiple coordination sites remains a challenging task. Such ve-membered heterocyclic ligands associated with hydrogen bonding as well as p-p interactions can lead to interesting features, such as exibility, ductility and chelation properties for the resulting coordination complexes.…”

3-Trifluoromethanesulfonyloxy-4,7-dihydropyrazolo[1,5-a]pyridine via Ring-Closing Metathesis: Synthesis and Transformation to Withasomnine Homologs

“…8 We have studied functionalization of pyrazoles at the C4-position via several types of metal-catalyzed coupling reactions, including the synthesis of oxygen-containing pyrazole heterobicyclic systems 4 (Scheme 1), which was developed using ring-closing metathesis (RCM) as the cyclization step. [9][10][11] In those studies, the N-1 position of the pyrazole ring was protected by a trityl or benzyl group. Provided the N-1 position was protected by an appropriate substituent group, RCM would, thus, enable the construction of various different types of pyrazole-fused hetero-bicyclic compounds.…”