Du Y, Li Q, Wang T, Wang YQ. Enantioselective Synthesis of Biphenyl-Bridged ϵ-Sultams by Organocatalytic Mannich Reactions of Cyclic N-Sulfonylimines with Unactivated Ketones.
Chemistry 2024;
30:e202302904. [PMID:
37936501 DOI:
10.1002/chem.202302904]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 11/06/2023] [Accepted: 11/07/2023] [Indexed: 11/09/2023]
Abstract
A highly enantioselective Mannich reaction of biphenyl-bridged seven-membered cyclic N-sulfonylimines with methyl alkyl ketones is disclosed in this study. The reaction was performed under organocatalysis by using a quinine-derived primary amine as the catalyst in combination with a Brønsted acid as the co-catalyst. High yields (up to 89 %) and excellent enantioselectivities (up to 97 % ee) were observed. For methyl alkyl ketones containing a larger alkyl substituent, specific regioselective addition to the C=N bond is favored at the methyl group. On the contrary, ketones containing a smaller alkyl substituent or hydroxyacetone substrates gave major syn selective Mannich products at the methylene group.
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