Han SB, Wei JY, Peng XC, Liu R, Gong SS, Sun Q. Hf(OTf)
4 as a Highly Potent Catalyst for the Synthesis of Mannich Bases under Solvent-Free Conditions.
Molecules 2020;
25:E388. [PMID:
31963465 PMCID:
PMC7024362 DOI:
10.3390/molecules25020388]
[Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 01/10/2020] [Accepted: 01/12/2020] [Indexed: 12/04/2022] Open
Abstract
Hf(OTf)4 was identified as a highly potent catalyst (0.1-0.5 mol%) for three-component Mannich reaction under solvent-free conditions. Hf(OTf)4-catalyzed Mannich reaction exhibited excellent regioselectivity and diastereoselectivity when alkyl ketones were employed as substrates. 1H NMR tracing of the H/D exchange reaction of ketones in MeOH-d4 indicated that Hf(OTf)4 could significantly promote the keto-enol tautomerization, thereby contributing to the acceleration of reaction rate.
Collapse