Probing Regio- and Enantioselectivity in the Formal [2 + 2] Cycloaddition of C(1)-Alkyl Ammonium Enolates with β- and α,β-Substituted Trifluoromethylenones
| Autor: | Wang, Yihong, Young, Claire Mary, Cordes, David Bradford, Slawin, Alexandra Martha Zoya, Smith, Andrew David |
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| Přispěvatelé: | EPSRC, University of St Andrews. School of Chemistry, University of St Andrews. EaSTCHEM, University of St Andrews. Institute of Behavioural and Neural Sciences |
| Rok vydání: | 2023 |
| Předmět: | |
| Zdroj: | The Journal of Organic Chemistry. |
| ISSN: | 1520-6904 0022-3263 |
| DOI: | 10.1021/acs.joc.2c02688 |
| Popis: | Funding: UK Engineering and Physical Sciences Research Council - EP/S019359/1; China Scholarship Council. The isothiourea-catalyzed regio- and enantioselective formal [2 + 2] cycloaddition of C(1)-alkyl and C(1)-unsubstituted ammonium enolates with β- and α,β-substituted trifluoromethylenones has been developed. In all cases, preferential [2 + 2]-cycloaddition over the alternative [4 + 2]-cycloaddition is observed, giving β-lactones with excellent diastereo- and enantioselectivity (34 examples, up to >95:5 dr, >99:1 er). The regioselectivity of the process was dictated by the nature of the substituents on both reaction components. Solely [2 + 2] cycloaddition products are observed when using α,β-substituted trifluoromethylenones or α-trialkylsilyl acetic acid derivatives; both [2 + 2] and [4 + 2] cycloaddition products are observed when using β-substituted trifluoromethylenones and α-alkyl-α-trialkylsilyl acetic acids as reactants, with the [2 + 2] cycloaddition as the major reaction product. The beneficial role of the α-silyl substituent within the acid component in this protocol has been demonstrated by control experiments. Publisher PDF |
| Databáze: | OpenAIRE |
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