Practical Enantioselective Reduction of Ketones Using Oxazaborolidine Catalysts Generated In Situ from Chiral Lactam Alcohols

Oxazaborolidine catalyst (CBS catalyst) has been extensively used for catalytic borane reduction with a predictable absolute stereochemistry and high enantioselectivity. However, the use of isolated CBS catalyst sometimes has the drawback of low reproducibility due to the aging of the CBS catalyst during storage. Therefore, we investigated a more reliable and practical method for the reduction of a variety of ketones including challenging substrates, primary aliphatic ketones, α,β-enones, and trifluoromethyl ketones. This review surveys the developments in borane reduction using oxazaborolidine catalysts generated in situ from chiral lactam alcohols and borane.

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Enantioselective Reduction of Ketones by in situ Generated Borane and Cbs Catalyst: Economical Alternative to Bh3-Thf

Synthetic Communications ◽

10.1080/00397919908085756 ◽

1999 ◽

Vol 29 (2) ◽

pp. 189-192 ◽

Cited By ~ 10

Author(s):

Alan Ford ◽

Simon Woodward

Keyword(s):

Enantioselective Reduction ◽

Economical Alternative ◽

Reduction Of Ketones

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Practical Enantioselective Reduction of Ketones Using Oxazaborolidine Catalyst Generated in situ from Chiral Lactam Alcohols and Borane.

ChemInform ◽

10.1002/chin.200405047 ◽

2004 ◽

Vol 35 (5) ◽

Author(s):

Yasuhiro Kawanami ◽

Shinichi Murao ◽

Takahiko Ohga ◽

Nobuyo Kobayashi

Keyword(s):

Enantioselective Reduction ◽

Reduction Of Ketones

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Enantioselective reduction of trifluoromethyl ketones using an oxazaborolidine catalyst generated in situ from a chiral lactam alcohol

Tetrahedron Asymmetry ◽

10.1016/j.tetasy.2011.08.006 ◽

2011 ◽

Vol 22 (13) ◽

pp. 1464-1466 ◽

Cited By ~ 7

Author(s):

Yasuhiro Kawanami ◽

Katsuhiro Hoshino ◽

Wataru Tsunoi

Keyword(s):

Enantioselective Reduction ◽

Trifluoromethyl Ketones

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Enantioselective Reduction of Aliphatic Ketones Using Oxazaborolidine Catalyst Generated In Situ from Chiral Lactam Alcohol and Phenoxyborane

Chemistry Letters ◽

10.1246/cl.2009.722 ◽

2009 ◽

Vol 38 (7) ◽

pp. 722-723 ◽

Cited By ~ 15

Author(s):

Yasuhiro Kawanami ◽

Yudai Mikami ◽

Katsuhiro Hoshino ◽

Mikiko Suzue ◽

Izumi Kajihara

Keyword(s):

Enantioselective Reduction ◽

Aliphatic Ketones

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Practical enantioselective reduction of ketones using oxazaborolidine catalyst generated in situ from chiral lactam alcohol and borane

Tetrahedron ◽

10.1016/j.tet.2003.08.064 ◽

2003 ◽

Vol 59 (42) ◽

pp. 8411-8414 ◽

Cited By ~ 23

Author(s):

Yasuhiro Kawanami ◽

Shinichi Murao ◽

Takahiko Ohga ◽

Nobuyo Kobayashi

Keyword(s):

Enantioselective Reduction ◽

Reduction Of Ketones

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Chiral Aminoalcohols and Squaric Acid Amides as Ligands for Asymmetric Borane Reduction of Ketones: Insight to In Situ Formed Catalytic System by DOSY and Multinuclear NMR Experiments

Molecules ◽

10.3390/molecules26226865 ◽

2021 ◽

Vol 26 (22) ◽

pp. 6865

Author(s):

Yana Nikolova ◽

Georgi M. Dobrikov ◽

Zhanina Petkova ◽

Pavletta Shestakova

Keyword(s):

Catalytic System ◽

Room Temperature ◽

Squaric Acid ◽

15N Nmr ◽

Mechanistic Insight ◽

15N Nmr Spectroscopy ◽

Mixture Prior ◽

Borane Reduction ◽

Reduction Of Ketones

A series of squaric acid amides (synthesized in 66–99% isolated yields) and a set of chiral aminoalcohols were comparatively studied as ligands in a model reaction of reduction of α-chloroacetophenone with BH3•SMe2. In all cases, the aminoalcohols demonstrated better efficiency (up to 94% ee), while only poor asymmetric induction was achieved with the corresponding squaramides. A mechanistic insight on the in situ formation and stability at room temperature of intermediates generated from ligands and borane as possible precursors of the oxazaborolidine-based catalytic system has been obtained by 1H DOSY and multinuclear 1D and 2D (1H, 10/11B, 13C, 15N) NMR spectroscopy of equimolar mixtures of borane and selected ligands. These results contribute to better understanding the complexity of the processes occurring in the reaction mixture prior to the possible oxazaborolidine formation, which play a crucial role on the degree of enantioselectivity achieved in the borane reduction of α-chloroacetophenone.

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