无溶剂硼酸高效合成螺杂双环衍生物

Efficient Solvent-free Synthesis of Spiro Heterobicyclic Derivatives with Boric Acid as Catalyst

在硼酸催化下,芳香醛、尿素和2,2-二甲基-1,3-二噁烷-4,6-二酮在无溶剂条件下合成了8种螺杂双环衍生物。当催化剂的用量为10%（摩尔分数）时,80℃反应2.0~4.0 h,收率为74%~93%。此外,还探讨了硼酸可能的催化机理。该方法具有条件温和,后处理工艺简单及收率高的优点。

Eight spiro heterobicyclic compounds were synthesized by the three component condensation reaction of aromatic aldehydes with urea and 2,2-dimethyl-1,3-dioxane-d ,6-dione using boric acid as catalyst under solvent-free conditions. The results indicate that the yields range from 84% to 94% at 80℃ for 2. 0 4.0 h using 10% molar fraction of boric acid （ relative to the substrate of 2,2-dimethyl-1,3-dioxane4,6- dione）. Furthermore, a mechanism for the reaction catalyzed by boric acid was proposed. The main advantages of the present procedure are mild conditions, short reaction time and high yields.