An Efficient Intramolecular 1,3-Dipolar Cycloaddition Involving 2-(1,2-Dichlorovinyloxy)aryldiazomethanes: A One-Pot Synthesis of Benzofuropyrazoles from Salicylaldehydes

Abstract

A novel intramolecular 1,3-dipolar cycloaddition strategy for a rapid entry into benzofuropyrazoles is described. In a three-step sequence, (E)-2-(1,2-dichlorovinyloxy)aryldiazomethanes were generated in situ from the corresponding salicylaldehydes. Intramolecular cycloaddition followed by dehydrohalogenation garnered 3-chlorobenzofuropyrazoles in excellent yields. By careful choice of solvent, base, and reaction conditions, the entire sequence can be carried out in a one-pot procedure.

Interference of H-bonding and substituent effects in nitro- and hydroxy-substituted salicylaldehydes

“…Salicylaldehyde is a compound with well-recognized significance in many branches of chemistry. It undergoes a variety of chemical reactions, very often being a key precursor for new compounds exhibiting diverse molecular structures and properties [1][2][3]. It is worth mentioning that the salicylaldehyde moiety appears in many compounds exhibiting various biological activity, including reactants used in the design of new inhibitors of HIV-1 integrase [4], or compounds exhibiting antiviral activity [5], as well as in reactions resulting in new compounds with anticancer [6,7] or antimicrobial activity [8].…”

Acetonitrile Activation: An Effective Two‐Carbon Unit for Cyclization

“…Despite their significance, the direct incorporation of either ethylene or acetylene into cyclic compounds is still very limited because of the gas‐phase reactants. Alternatively, trihaloethenes were used as C2 building blocks in cycloaddition reactions, such as Diels–Alder reactions, [2+2] cycloadditions, and 1,3‐dipolar cycloadditions (Scheme a). However, the toxicity and the multiple‐step preparation of trihaloethene substrates restrict their further application.…”

Facile synthesis of 5-bromotropono[${c}$]-fused pyrazoles and isoxazole

“…39 Considering these results, we attempted to use the corresponding arylhydrazine hydrochloride as the reaction partner as shown in Scheme 2. To our delight, an improvement in terms of yields and reaction time was achieved, and the desired 1-aryl-5-bromo-3-methyltropono[c ]pyrazoles (10)(11)(12)(13)(14)(15) were obtained in satisfactory yields of 56%-77% after 12 h. The reaction results are summarized in the Table. As shown in the Table, all the desired products were obtained in satisfactory yields except for compounds 14 and 15 (entries 6 and 7). The products 14 and 15 were obtained in moderate yields of 60% and 52%, respectively, which we attributed to the strong electron-withdrawing effects of the CN and NO 2 groups, which rendered the condensation reaction unfavorable.…”

“…1,2 In particular, the important role of ring-fused pyrazoles in medicinal and pharmaceutical chemistry is indisputable and well reflected by a large number of recent publications, 3−6 including some excellent reviews. 7,8 Most fused pyrazole compounds reported in the literature comprise a common heterocyclic ring moiety, such as pyrazolopyrimidine, 9 pyrazolopyridine, 10 pyrazoloquinoline, 11 pyrazoloindol, 12 benzofuropyrazole, 13 benzopyranopyrazole, 14 and synthetic analogues thereof. In addition, as is well known, the ring-fused isoxazole skeleton is also an important structural unit that can be found in various bioactive compounds such as those with anti-HIV, 15 antifungal, 16 and nematicidal properties.…”