been successfully realized for the first time using 0.1 mol % of borane catalyst generated in situ by hydroboration of pentafluorostyrene with HB(C6F5)2 to afford a variety of chromanones and flavanones in 60–99% yields. An attempt for the asymmetric transformation with chiral diyne and HB(C6F5)2 gave chromanones and flavanones in high yields with up to 32% ee.
An efficient synthesis of bioactive chiralflavanones (1) was achieved through the Rh-catalyzed asymmetric1,4-addition of arylboronicacid to chromone. The reaction in toluene proceeded smoothly at room temperature in the presence of 0.5% Rh catalyst with electron-poor chiral diphosphine MeO-F12-BIPHEP. In this reaction, the 1,2-addition to (S)-1 frequently occurred to yield (2S,4R)-2,4-diaryl-4-chromanol
Enantioselective biomimetic cyclization of 2′-hydroxychalcones to flavanones
作者:Yan-Lei Zhang、Yong-Qiang Wang
DOI:10.1016/j.tetlet.2014.04.032
日期:2014.5
developed and shown to catalyze the direct and highly enantioselective cyclization of 2′-hydroxychalcones in imitation of the natural process of chalcone cyclization. The straightforward synthetic process occurs under mild reaction conditions, tolerates moisture and air, and gives an enantiomeric excess up to 99%. This approach provides a facile and efficient access to chiral flavanones.