The sodium hydride/dibenzo-18-crown-6 ether system was found to be an effective base for the synthesis of 1,3-diketones by the Claisen condensation. The use of potassium fluoride (with or without crown ether) as the base in diazo-transfer reactions extends this reaction to the synthesis of hindered diazo diketones. In the case of isomeric 1,3-diketones, the stereoselectivity of the process considerably rises.
氢化
钠/二苯并-
18-冠-6醚体系被发现是通过克莱森缩合合成1,3-二酮的有效碱。使用
氟化
钾(有或没有
冠醚)作为二氮转移反应中的碱,将该反应扩展到合成受阻的二氮二酮。在异构体1,3-二酮的情况下,反应的立体选择性显著提高。