A methylenation–cyclization reaction, employing cyclic enaminones with primary aromatic amines and two molecules of CO₂, furnishing fused-tetrahydropyrimidines, is discussed. In this Cs₂CO₃ and ZnI₂ catalyzed one-pot two-step procedure, two molecules of CO₂ were selectively converted to methylene groups. The multi-component reaction might proceed through the formation of bis(silyl)acetal which was followed by condensation and further aza-Diels–Alder reaction. Hydroquinazoline, hydrocyclopenta[d]pyrimidine and hydroindeno[1,2-d]pyrimidine derivatives could be prepared with CO₂ as the C1 source, effectively.

中文翻译：

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稠合四氢嘧啶的合成：利用两分子 CO2 的一锅亚甲基化环化。

讨论了使用环状烯胺酮与伯芳香胺和两个 CO ₂分子，提供稠合四氢嘧啶的亚甲基化-环化反应。在这个Cs ₂ CO ₃和ZnI ₂催化的一锅两步法中，两个CO ₂分子被选择性地转化为亚甲基。多组分反应可能通过形成双（甲硅烷基）缩醛进行，然后是缩合和进一步的氮杂-狄尔斯-阿尔德反应。氢喹唑啉、氢环戊二烯[ d ]嘧啶和氢茚并[1,2- d ]嘧啶衍生物可以以CO ₂作为C1源有效地制备。