A general method for the preparation of 2,2-disubstituted 1-nitroalkenes
摘要:
A general and expeditious routs for the preparation of functionalized 2,2-disubstituted 1-nitroalkenes has been developed. Conjugate 1,4-addition of complex zinc cuprates (RCu(CN)ZnI) to easily obtained (E)-1-nitroalkenes, followed by trapping with phenylselenenyl bromide and subsequent oxidative elimination, afforded the corresponding 2,2-disubstituted 1-nitroalkenes in good yields. 2-Alkyl-2-aryl- and 2,2-dialkyl nitroalkenes 4b-g were prepared in 76-88% yield and obtained as E/Z isomeric mixtures, slightly favoring the Z isomer (approximately 1.0:1.5, E/Z).
Reductive biotransformation of nitroalkenes via nitroso-intermediates to oxazetes catalyzed by xenobiotic reductase A (XenA)
作者:Katharina Durchschein、Walter M. F. Fabian、Peter Macheroux、Klaus Zangger、Gregor Trimmel、Kurt Faber
DOI:10.1039/c0ob01216e
日期:——
A novel reductive biotransformation pathway for β,β-disubstituted nitroalkenes catalyzed by flavoproteins from the Old Yellow Enzyme (OYE) family was elucidated. It was shown to proceed via enzymatic reduction of the nitro-moiety to furnish the corresponding nitroso-alkene, which underwent spontaneous (non-enzymatic) electrocyclization to form highly strained 1,2-oxazete derivatives. At elevated temperatures the latter lost HCN via a retro-[2 + 2]-cycloaddition to form the corresponding ketones. This pathway was particularly dominant using xenobiotic reductase A, while pentaerythritol tetranitrate-reductase predominantly catalyzed the biodegradation via the Nef-pathway.
A modularsugar-based phosphoroamidite L1–L5a–g and phosphite L6–L9a–g ligandlibrary was tested in the asymmetric Cu-catalyzed 1,4-conjugate addition reactions of β-substituted (cyclic and linear) and β,β′-disubstituted (cyclic) enones. The selectivity depended strongly on the configuration of carbon atom C-3, the size of the sugar backbone ring, the flexibility of the ligand backbone, the substituents
Building the buildingblocks: A highly enantioselective hydrogenation of β‐aryl‐β‐alkyl disubstituted nitroalkenes 1 has been developed. This method results in enantiomericallypure nitroalkanes 2, which are versatile precursors for chemical synthesis.
mild and chemodivergent transformation involving nitroalkanes has been developed. Under optimized reaction conditions, in the presence of trichlorosilane and a tertiary amine, aliphatic nitroalkanes were selectively converted into amines or nitriles. Furthermore, when chiral β-substituted nitrocompounds were reacted, the stereochemical integrity of the stereocenter was maintained and α-functionalized
Boosting Conjugate Addition to Nitroolefins Using Lithium Tetraorganozincates: Synthetic Strategies and Structural Insights
作者:Marzia Dell'Aera、Filippo Maria Perna、Paola Vitale、Angela Altomare、Alessandro Palmieri、Lewis C. H. Maddock、Leonie J. Bole、Alan R. Kennedy、Eva Hevia、Vito Capriati
DOI:10.1002/chem.202001294
日期:2020.7.17
We report the first transition metal catalyst‐ and ligand‐free conjugateaddition of lithium tetraorganozincates (R4ZnLi2) to nitroolefins. Displaying enhanced nucleophilicity combined with unique chemoselectivity and functional group tolerance, homoleptic aliphatic and aromatic R4ZnLi2 provide access to valuable nitroalkanes in up to 98 % yield under mild conditions (0 °C) and short reaction time