Nitrogen bridgehead compounds. Part 30. Vilsmeier-Haack formylation of 6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-4-ones

Ágnes Horváth, István Hermecz, Lelle Vasvári-Debreczy, Kálmán Simon, Marianne Pongor-Csákvári, Zoltán Mészáros, Gábor Tóth

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Abstract

Depending on the substituents at C(3) and on the reaction conditions, Vilsmeier - Haack formylation (POCl3 - DMF) of 6,7,8,9-tetrahydro-4H- pyrido[1,2-a]pyrimidin-4-ones (I) led to 9-(dimethylamino-methylene)- or 9-(ethoxymethylene)-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidines (II) and (IV), respectively, or 9-formyl-1,6,7,8-tetrahydro-4H-pyrido[1,2-a]pyrimidines (III). Compounds (II) may be converted into (III) or (IV). Owing to the enhanced activity of their 9-CH2 group, the 3-carboxylic acid derivatives of (I) form compounds (II) even on the action of dimethylformamide diethyl acetal, and compounds (IV) on the action of triethyl orthoformate in Ac2O. Compounds (III) may be converted back into (I) by hydrolysing the 9-formyl group. Their spectral data show that compounds (II) and (IV) exist exclusively in the E-configuration, and compounds (III) predominantly in the 1,6,7,8-tetrahydro-tautomeric form.

Original languageEnglish
Pages (from-to)369-377
Number of pages9
JournalJournal of the Chemical Society, Perkin Transactions 1
Publication statusPublished - Dec 1 1983

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  • Chemistry(all)

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