Facile Synthesis of (3,5-(CF3)2C6H3)2BX (X = H, OMe, F, Cl, Br): Reagents for the Introduction of a Strong Boryl Acceptor Unit

The reaction of (3,5-(CF3)2C6H3)Li ((Fxyl)­Li) with BH3·SMe2 in Et2O furnishes Li­[(Fxyl)­BH3] in an essentially quantitative yield. Hydride abstraction with Me3SiCl followed by the addition of a second equivalent of (Fxyl)Li gives Li­[(Fxyl)2BH2] in 71% yield. Treatment of Li­[(Fxyl)2BH2] with 1 equiv of Me3SiCl and a subsequent targeted methanolysis provide access to the methoxyborane (Fxyl)2BOMe. The latter compound serves as starting material for the synthesis of the haloboranes (Fxyl)2BX (X = F, Cl, Br) through the reaction with KHF2/Me3SiCl, BCl3, and BBr3, respectively. All three haloboranes, as well as key synthesis intermediates, have been structurally characterized by X-ray crystallo­graphy.