TiCl4-mediated reduction of 1,3-diketones with BH3-pyridine complex: A highly diastereoselective method for the synthesis of syn-1,3-diols

[GRAPHICS] 1,3-Diketones can be reduced in high yields and with excellent diastereosel ectivity to the corresponding syn-1,3-diols by carrying out the reaction wi th BH3-pyridine complex in CH2Cl2 at -78 degrees C in the presence of an eq uivalent of TiCl4 and 0.1 equiv of pyridine. This protocol shows a general character: excellent results are obtained when the groups bound to the carb onylic functions are linear or branched carbon chains and aromatic or benzy lic frameworks as well.