{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T00:12:35Z","timestamp":1759968755523,"version":"build-2065373602"},"reference-count":26,"publisher":"Wiley","issue":"10","license":[{"start":{"date-parts":[[2023,8,29]],"date-time":"2023-08-29T00:00:00Z","timestamp":1693267200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["aces.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Asian J Org Chem"],"published-print":{"date-parts":[[2023,10]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>Pyrimido[5,4\u2010<jats:italic>d<\/jats:italic>]pyrimidines are biologically important compounds with diverse activity depending on the substituent groups around the heterocycle. The 3,4\u2010dihydropyrimido[5,4\u2010<jats:italic>d<\/jats:italic>]pyrimidines are efficiently converted to the aromatic derivatives by Dimroth rearrangement promoted by reaction with piperidine, in a very slow process. Subsequently, the aromatic derivatives are converted to new 4,8\u2010disubstituted\u2010pyrimido[5,4\u2010<jats:italic>d<\/jats:italic>]pyrimidine derivatives by reaction with aldehydes in an acidic medium. The 4,8\u2010disubstituted\u2010pyrimido[5,4\u2010<jats:italic>d<\/jats:italic>]pyrimidines are also obtained much more efficiently by a tandem reaction between the 3,4\u2010dihydropyrimido[5,4\u2010<jats:italic>d<\/jats:italic>]pyrimidines, piperidine and a variety of aldehydes. The cascade reaction approach has a broad application since phenyl, haloaryl, alkoxy\u2010aryl, hydroxy\u2010aryl, and heteroaryl aldehydes are compatible with the reaction conditions. The reactions were studied by <jats:sup>1<\/jats:sup>H NMR. These studies support the reaction mechanisms proposals. The tandem approach involves the formation of ionic reactive intermediates that allows explain this approach's efficiency.<\/jats:p>","DOI":"10.1002\/ajoc.202300251","type":"journal-article","created":{"date-parts":[[2023,8,22]],"date-time":"2023-08-22T07:42:33Z","timestamp":1692690153000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["A Tandem Reaction in the Synthesis of New 4,8\u2010Disubstituted\u2010pyrimido[5,4\u2010<i>d<\/i>]pyrimidine Derivatives"],"prefix":"10.1002","volume":"12","author":[{"given":"Ashly","family":"Rocha","sequence":"first","affiliation":[{"name":"Centre of Chemistry, Departamento de Qu\u00edmica, Escola de Ci\u00eancias Universidade do Minho  Campus de Gualtar 4710-057 Braga Portugal"}]},{"given":"Andr\u00e9","family":"Lopes","sequence":"additional","affiliation":[{"name":"Centre of Chemistry, Departamento de Qu\u00edmica, Escola de Ci\u00eancias Universidade do Minho  Campus de Gualtar 4710-057 Braga Portugal"}]},{"given":"Sofia","family":"Teixeira","sequence":"additional","affiliation":[{"name":"Centre of Chemistry, Departamento de Qu\u00edmica, Escola de Ci\u00eancias Universidade do Minho  Campus de Gualtar 4710-057 Braga Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8666-0362","authenticated-orcid":false,"given":"M. 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