Synthesis, Structure, and E−Z Isomerization of β-(Hetero)aryl-α-nitro-α,β-enals
| Autor: | Ricardo Alonso, Krzysztof Kierus, Luis F. Roa, Marta Fernández-González, Juan Carlos Ortiz-Lara, Lidia Ozores-Viturro, Fernando Cagide-Fagín, Patricia Martínez-Bescos |
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| Rok vydání: | 2008 |
| Předmět: | |
| Zdroj: | The Journal of Organic Chemistry. 73:3745-3753 |
| ISSN: | 1520-6904 0022-3263 |
| Popis: | (Chemical Equation Presented) The first general methodology for the gram-scale preparation of previously overlooked β-(hetero)aryl-α- nitro-α,β-enals (3) is reported. Condensation of (hetero)aromatic aldehydes with 2-nitroethanol gave the E-isomers of uncommon β-(hetero)aryl-α-hydroxymethyl-α,β-unsatured-nitroalkenes (2), as determined by NOE and X-ray studies. α-Nitro-α,β-enals 3 were subsequently obtained by hypervalent iodine oxidation of 2 as E-Z-mixtures in solid form. They showed varied stability and solvent-dependent thermal-promoted and photopromoted E-Z interconversion. Starting with furfural, experimental conditions were developed to prepare the corresponding nitroenal 3a enriched in either the E or the Z isomer: E-3a/Z-3a ≈ 90/10 and 20/80, respectively. In contrast with other structurally related compounds, nitroenals 3 have their (hetero)aryl-vinyl unit and their formyl and nitro groups all in a planar arrangement, both in solid form and in solution; accordingly, they are colored compounds with predicted high dipole moments. As deduced from solution-NMR and X-ray data, the C=C and the C=O double bonds in 3 are exclusively s-cis-oriented; this disposition corresponds in fact to the DFT-computed most stable conformer. © 2008 American Chemical Society. |
| Databáze: | OpenAIRE |
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