Maľučká LU, Vilková M. Spectral Assignment in the [3 + 2] Cycloadditions of Methyl (2
E)-3-(Acridin-4-yl)-prop-2-enoate and 4-[(
E)-2-Phenylethenyl]acridin with Unstable Nitrile N-Oxides.
Molecules 2024;
29:2756. [PMID:
38930822 PMCID:
PMC11206844 DOI:
10.3390/molecules29122756]
[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: 05/12/2024] [Revised: 06/06/2024] [Accepted: 06/06/2024] [Indexed: 06/28/2024] Open
Abstract
The investigation of cycloaddition reactions involving acridine-based dipolarophiles revealed distinct regioselectivity patterns influenced mainly by the electronic factor. Specifically, the reactions of methyl-(2E)-3-(acridin-4-yl)-prop-2-enoate and 4-[(1E)-2-phenylethenyl]acridine with unstable benzonitrile N-oxides were studied. For methyl-(2E)-3-(acridin-4-yl)-prop-2-enoate, the formation of two regioisomers favoured the 5-(acridin-4-yl)-4,5-dihydro-1,2-oxazole-4-carboxylates, with remarkable exclusivity in the case of 4-methoxybenzonitrile oxide. Conversely, 4-[(1E)-2-phenylethenyl]acridine displayed reversed regioselectivity, favouring products 4-[3-(substituted phenyl)-5-phenyl-4,5-dihydro-1,2-oxazol-4-yl]acridine. Subsequent hydrolysis of isolated methyl 5-(acridin-4-yl)-3-phenyl-4,5-dihydro-1,2-oxazole-4-carboxylates resulted in the production of carboxylic acids, with nearly complete conversion. During NMR measurements of carboxylic acids in CDCl3, decarboxylation was observed, indicating the formation of a new prochiral carbon centre C-4, further confirmed by a noticeable colour change. Overall, this investigation provides valuable insights into regioselectivity in cycloaddition reactions and subsequent transformations, suggesting potential applications across diverse scientific domains.
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