Synthesis and application of chiral hydrobenzoin

Hydrobenzoin (1,2-diphenyl-1,2-ethanediol) and its derivatives have been used in various areas of chiral chemistry and have broadened their range of applications in synthetic chemistry. Hydrobenzoin has a long history from the beginning of chiral chemistry; and recent advance in preparation method of chiral hydrobenzoin dramatically improved its availability and expanded its application in organic synthesis. In the early days, chiral hydrobenzoins had been prepared by optical resolution . But along with the development of asymmetric oxidation and reduction technology, asymmetric synthesis from stilbenes or benzoins has been widely explored. Recently, direct synthesis by asymmetric pinacol coupling from benzaldehydes is under development. Chiral hydrobenzoins had been used mainly as chiral auxiliary or other stoichiometric use during several decades. However, catalytic application is increasing recently. This review summarizes the synthesis and application of chiral hydrobenzoin, and focus on the chemistry of hydrobenzoin and its derivatives and cover the historical background to its updated utilization.