p-TSA catalyzed 6-endo-trig/dig cyclization of 5-aminopyrazoles and 3°/2°-propargylic alcohols: access to pyrazolo[1,5-a]dihydropyrimidines and pyrazolo[3,4-b]pyridines.
{"title":"<i>p</i>-TSA catalyzed 6-<i>endo-trig</i>/<i>dig</i> cyclization of 5-aminopyrazoles and 3°/2°-propargylic alcohols: access to pyrazolo[1,5-<i>a</i>]dihydropyrimidines and pyrazolo[3,4-<i>b</i>]pyridines.","authors":"Nagaraju Medishetti, Bhanu Prasad Banda, Krishnaiah Atmakur","doi":"10.1039/d4ob01255k","DOIUrl":null,"url":null,"abstract":"<p><p>A facile, straightforward synthesis of fused pyrazolo[1,5-<i>a</i>]dihydropyrimidines and pyrazolo[3,4-<i>b</i>]pyridines is accomplished by using 5-aminopyrazoles, 3°/2°-propargylic alcohols and ynones in the presence of <i>p</i>-TSA. The reaction proceeds through allenylation (<i>N</i>-alkylation)/propargylation (<i>C</i>-alkylation) of 5-aminopyrazoles, followed by intramolecular 6-<i>endo-trig</i>/<i>dig</i> cyclization leading to the title products with the formation of new C-N and C-C bonds. Operationally simple reaction conditions, inexpensive reagents, better yields, and gram-scale synthesis are the advantages of this protocol.</p>","PeriodicalId":96,"journal":{"name":"Organic & Biomolecular Chemistry","volume":null,"pages":null},"PeriodicalIF":2.9000,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Organic & Biomolecular Chemistry","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1039/d4ob01255k","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, ORGANIC","Score":null,"Total":0}
引用次数: 0
Abstract
A facile, straightforward synthesis of fused pyrazolo[1,5-a]dihydropyrimidines and pyrazolo[3,4-b]pyridines is accomplished by using 5-aminopyrazoles, 3°/2°-propargylic alcohols and ynones in the presence of p-TSA. The reaction proceeds through allenylation (N-alkylation)/propargylation (C-alkylation) of 5-aminopyrazoles, followed by intramolecular 6-endo-trig/dig cyclization leading to the title products with the formation of new C-N and C-C bonds. Operationally simple reaction conditions, inexpensive reagents, better yields, and gram-scale synthesis are the advantages of this protocol.