Vilsmeier and Mannich reactions on (4S)-N2-substituted 4-methyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones

✍ Scribed by María Fernandez; María L. Heredia; Elena de la Cuesta; Carmen Avendaño

• Book ID: 104209132
• Publisher: Elsevier Science
• Year: 1998
• Tongue: French
• Weight: 351 KB
• Volume: 54
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(98)83013-5

✦ Synopsis

The enamine character of the CH2-C(lla)=N(ll) fragment in the title compounds was studied. Congxatmds I gave l-dimethylaminomethylene products $ after Vilsmeier reaction. The l-formyl derivatives, obtained by alkaline hydrolysis of 5, were isolated as enol tautome~s and were vea'y unstable in acid medic On the other hand, acid-promoted elimination of dimelhylamine from the Mannich reaction products 7 gave 1-methylene derivatives 8, which showed an interesting reactivity. Thus, 8a dimerized in acid to the ethylidene derivative 9a. 1,4-Dialkyl-compounds 7 and 9a showed a 1,4-syn-stereochemistry.