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