Asymmetric Transfer Hydrogenation of Aryl Heteroaryl Ketones using Noyori‐Ikariya Catalysts. Issue 20 (18th August 2021)

• Record Type: Journal Article
• Authors: Zheng, Ye; Martinez‐Acosta, Jaime A.; Khimji, Mohammed; Barbosa, Luiz C. A.; Clarkson, Guy J.; Wills, Martin
• Is Part Of: ChemCatChem. Volume 13:Issue 20(2021)
• Page Start: 4384
• Page End: 4391
• Publication Date: 2021-08-18
• Subjects: asymmetric -- transfer -- hydrogenation -- heterocycle -- alcohol; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.202101027
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: A range of ketones flanked by a combination of an aromatic and a heterocyclic ring (furan, thiophene, N ‐methylimidazole) were reduced under asymmetric transfer hydrogenation (ATH) conditions. Using a range of [(arene)Ru(TsDPEN)Cl] precatalysts, including tethered derivatives, the reduction enantioselectivity was high (up to 99 % ee) in cases where the aromatic ring contained an ortho ‐substituent. The enantioselectivity is influenced by a combination of steric and electronic factors which for the furan and thiophene series, follow literature precedents. In the case of the N ‐methylimidazole‐containing ketones, an unexpected switch in enantioselectivity took place upon variation of the opposing aromatic group. Pyrrole‐ containing ketones were resistant to reduction. This study demonstrates the asymmetric transfer hydrogenation (ATH) of a range of hindered heterocyclic ketones, in high conversion and ee, using Noyori‐Ikariya catalysts. Abstract : A systematic study of the asymmetric transfer hydrogenation (AH), using [arene/Ru(II)/TsDPEN] pre‐catalysts, of a range of heterocyclic ketones is described. The products are formed in very high ee in cases where an ortho‐ substituted aromatic ring opposes the heterocycle on the ketone group. This provides a practical and selective access to a range of hetereocyclic alcohols in high ee, for the by ATH using Noyori‐Ikariya catalysts.