Synthesis and regioselectivity of the [3,3]-sigmatropic rearrangement of substituted 2-allylthio- and 2-allylseleno-1,4-dihydropyridines
摘要:
The reaction of 3-cyano-1,4-dihydropyridine-2-thiolates and the corresponding selenolates with allyl bromide gave 2-allylthio- and 2-allylseleno-3-cyano-1,4-dihydropyridines, which, upon heating in various solvents or in the solid state, undergo [3,3]-sigmatropic rearrangement to give 3-cyano-3-allyl-1,2,3,4-tetrahydropyridine-2-thiones and the corresponding selenones. The resultant pyridinethiones are alkylated by alkyl halides at the sulfur atom and are oxidized by iodine to give disulfides.
Cross-linked polystyrene-TiCl4 complex as a reusable Lewis acid catalyst for solvent-free Knoevenagel condensations of 1,3-dicarbonyl compounds with aldehydes
作者:Ali Rahmatpour、Niloofar Goodarzi
DOI:10.1016/j.catcom.2018.11.001
日期:2019.5
in the range of (50–80 mesh size) were prepared by a new method, characterized and functionalized with titaniumtetrachloride to afford the corresponding polystyrene‑titaniumtetrachloridecomplex in one step reaction and characterized by FT-IR, UV, TGA, DSC, XRD, SEM, BET. This polymer metal complex (PS/TiCl4) was used as a heterogeneous, recoverable, reusable Lewis acid for solvent-free Knoevenagel
utilized as an efficient heterogeneous recyclable catalyst for Knoevenagel condensationbetween poorly reactive β-diketones and aldehydes under solvent-free conditions. This protocol also works well with more reactive β-ketoesters. The condensation is efficient, clean, and mild. The scope and generality of the Knoevenagel condensation were investigated. The procedure led only to the Knoevenagel product,
A simple method for the preparation of functionalized trisubstituted alkenes and α,β,γ,δ-unsaturated carbonyl compounds by using natural amino acid l-tryptophan
作者:Ying Hu、Yan-Hong He、Zhi Guan
DOI:10.1016/j.catcom.2010.01.016
日期:2010.3
reactive acetylacetone and ethyl acetoacetate. The reactions were carried out at room temperature and gave good yields. It is a convenient entry for preparation of functionalizedtrisubstituted alkenes and α,β,γ,δ-unsaturated carbonyl compounds.
Biocatalytic Knoevenagel reaction using alkaline protease from<i>Bacillus licheniformis</i>
作者:Bang-Hua Xie、Zhi Guan、Yan-Hong He
DOI:10.3109/10242422.2012.662961
日期:2012.3
condensations of aromatic, hetero-aromatic and α;β-unsaturated aldehydes with less reactive acetylacetone or ethyl acetoacetate. The reactions were performed in organic solvent in the presence of water. The functionalized trisubstituted alkenes and α,β,γ,δ-unsaturated carbonylcompounds could be obtained in moderate to good yields with E/Z selectivities up to >99:1. This biocatalytic reaction provided an alternative
Enzyme catalytic promiscuity: The papain-catalyzed Knoevenagel reaction
作者:Wen Hu、Zhi Guan、Xiang Deng、Yan-Hong He
DOI:10.1016/j.biochi.2011.09.018
日期:2012.3
Knoevenagel reactions in DMSO/water. A wide range of aromatic, hetero-aromatic and α,β-unsaturated aldehydes could react with less active methylene compounds acetylacetone and ethyl acetoacetate. The products were obtained in moderate to excellent yields with Z/E selectivities of up to 100:0. This case of biocatalytic promiscuity not only widens the application of papain to new chemical transformations