Synthesis of 2,3-dihydroimidazo[1,2-a]pyrimidin-5(1H)-ones by the domino Michael addition retro-ene reaction of 2-alkoxyiminoimidazolidines and acetylene carboxylates
作者:Jarosław Sączewski、Zdzisław Brzozowski、Maria Gdaniec
DOI:10.1016/j.tet.2005.03.063
日期:2005.5
2-Alkoxyiminoimidazolidines 2–3 react with acetylene dicarboxylates and ethyl phenylpropiolate to give 8-alkoxy-imidazo[1,2-a]pyrimidin-5(3H)-ones C, which subsequently undergo a sterically induced multihetero-retro-ene fragmentation to give imidazo[1,2-a]pyrimidin-5(1H)-ones 4–7 together with formaldehyde or benzaldehyde. On the other hand, a similar reaction of 2–3 with ethyl propiolate gives corresponding
2- Alkoxyiminoimidazolidines 2 - 3与乙炔二羧酸酯和乙基苯基丙,得到8 -烷氧基-咪唑并做出反应[1,2一]嘧啶5(3 ħ) -酮Ç,其随后经历空间诱导multihetero复古烯碎片得到咪唑并[1,2一]嘧啶5(1 ħ) -酮4 - 7与甲醛或苯甲醛在一起。在另一方面中,一个类似的反应2 - 3与丙炔酸乙酯给出对应8 -烷氧基-咪唑并[1,2一]嘧啶5(3 ħ) -酮8 - 10。未取代的咪唑并[1,2 - a ]嘧啶-5(1 H)-one 11可以通过在回流乙醇中长时间加热9的逆烯反应来制备。据报道,使用DMF /磺酰氯作为新的Vilsmeier型N-甲酰化试剂,直接合成1-甲酰基-7-苯基-咪唑并[1,2- a ]嘧啶-5(1 H)-one 14的方法。