Aldol condensations in pyrazino[2,1-b]quinazolines. Fast access to seco-ardeemin derivatives

作者：Cledera Pilar; Villacampa Mercedes; Avendano Carmen; Carlos Menendez J

来源：ARKIVOC, 2011, 72-98.

• Aldol condensation
• pyrazino[2,1-b]quinazolines
• diastereoselectivity
• catalytic hydrogenation
• benzene hydrogenation

The reaction between 2-alkylpyrazino[2,1-b]quinazoline-3,6-diones and aromatic aldehydes in the presence of KO(t)Bu afforded the corresponding 1-arylmethylene derivatives, preferently as the Z isomers. This diastereoselectivity was the result of thermodynamic control, as shown by ab initio calculations. These aldol reactions proceeded with partial racemization of the C-4 stereocenter, in contrast with the condensations of the related 2-acetylpyrazino[2,1-b]quinazoline-3,6-diones. Catalytic hydrogenation of the 1-arylmethylene derivatives obtained through these condensations afforded cis-1,4-disubstituted pyrazino[2,1-b]quinazoline-3,6-diones, normally with complete diastereoselectivity, but these reactions had compounds from partial reduction of the benzene ring as side products.

• 出版日期2011