Site-selectivity control in hetero-Diels-Alder reactions of methylidene derivatives of lawsone through modification of the reactive carbonyl group: an experimental and theoretical study
| Autor: | Evangelos G. Bakalbassis, Luis R. Domingo, Maria Tsanakopoulou, Marina A Tzani, Erifili Tsovaltzi, Elizabeth Malamidou-Xenikaki, Periklis Selevos |
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| Rok vydání: | 2019 |
| Předmět: |
Tandem
010405 organic chemistry Chemistry Site selectivity Organic Chemistry Acetal 010402 general chemistry 01 natural sciences Biochemistry Medicinal chemistry 0104 chemical sciences Catalysis Lawsone chemistry.chemical_compound Derivative (finance) Knoevenagel condensation Reactivity (chemistry) Physical and Theoretical Chemistry |
| Zdroj: | Organicbiomolecular chemistry. 17(3) |
| ISSN: | 1477-0539 |
| Popis: | A new perspective on the reactivity of hydroxyquinones was revealed as an acetal derivative of lawsone was synthesized, isolated, and used in tandem Knoevenagel/hetero-Diels-Alder reactions catalyzed by S-proline. The intermediate alkylidene-1,3-diones that were formed in situ reacted with electron rich alkenes to predominantly afford pyrano-1,2-naphthoquinone (β-lapachone) derivatives along with the isomeric pyrano-1,4-naphthoquinone (α-lapachone) derivatives in high to excellent total yields. Interestingly, the highly reactive arylidene-1,3-dione derivatives were found to be stable and isolable. DFT calculations suggest that these hetero-Diels-Alder reactions have a high polar character, taking place through a two-stage one-step mechanism. An analysis of the conceptual DFT indices allows explaining the remarkable site-selectivity observed. |
| Databáze: | OpenAIRE |
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