Intramolecular cyclization reactions of pyrimidinium cations

✍ Scribed by A.E. Frissen; G. Geurtsen; A.T.M. Marcelis; H.C. van der Plas

• Publisher: Elsevier Science
• Year: 1990
• Tongue: French
• Weight: 858 KB
• Volume: 46
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)85440-5

✦ Synopsis

N-alkylpyrimidinium cations carrying a dienophilic side-chain at the 2-or 5position undergo intramolecular inverse electron demand Diels-Alder reactions into the corresponding annelated pyridine derivatives under considerably milder conditions than the corresponding neutral pyrimidines. Protonation of the p imidine ring also facilitates the intramolecular Diels-Alder reaction. Protonation o r less activated pyrimidines leads, however, to products resulting from an intramolecular coplanar cycloamination reaction.