Chiral Ion‐Pair Organocatalyst‐Promoted Efficient Enantio‐selective Reduction of α‐Hydroxy Ketones

Abstract

The enantioselective reduction of ahydroxy ketones with catecholborane has been developed employing 5 mol% of an 1,1'-bi-2-naphthol (BINOL)-derived ion-pair organocatalyst. This methodology provides a straightforward access to the corresponding aromatic 1,2-diols in high yields (up to 90%) with excellent enantioselectivities (up to 97%). Furthermore, the a-amino ketones also could be reduced with moderate ee values under mild reaction condition.

Recent Advances in Organocatalyzed Asymmetric Reduction of Prochiral Ketones: An Update

“…Figure 4 The structure of CPA catalyst and proposed transition state for asymmetric reduction of ketones Following this pioneering work, the group of Shi demonstrated in a 2018 report 29 that the similar catalyst system could be used for effective asymmetric reduction of aryl hydroxy ketones. Generally, high yields (74-90%) and excellent ees were obtained for a broad series of substrates (85-97% ee).…”

“…Following this pioneering work, Shi's group demonstrated in a 2018 report 28 that a similar catalyst system could be used for effective asymmetric reduction of aryl hydroxy ketones. Generally, high yields (74-90%) and excellent ee values (85-97%) were obtained for a broad series of substrates.…”

Organocatalytic hydroboration of carbonyl compounds promoted by choline-based ionic liquids

“…Similarly, P-containing heterocycles such as 1,3,2-diazaphospholene, 22 phosphenium triflate, 23 triazaphospholene halides (TAP) 24 or carbodiphosphorane 25 have been applied in boron-hydrogen bond addition to C=O bonds. Moreover, the use of binol-derived phosphoric acids 26,27 or thioureaamine complex 28 allows the enantioselective reduction of ketones. However, in most cases of organocatalytic hydroboration of carbonyl compounds, the catalysts were not commercially available, their preparation was not trivial, or the process itself had to be carried out in an inert atmosphere.…”