Chiral borated esters in asymmetric synthesis: 1. the first asymmetric reaction catalyzed by chiral spiroborated esters with an O₃BN framework

The first asymmetric reaction catalyzed by chiral spiroborated esters with an O₃BN framework was reported. In the presence of 0.1 equivalent of (R,S)-1 or (S,S)-1, acetophenone was reduced by 0.6 equivalent of borne in THF at 0–5 °C for 2 h to give (R)-1-phenylethanol of up to 76% ee and 73% isolated yield. Influence of reaction conditions on the stereoselectivity of the reduction was investigated and a possible catalytic mechanism of the chiral spiroborated esters toward the reduction was also suggested.