Oxydehydrogenative aromatization of fused 3-aminopyran-2-ones on carbon surfaces: a simple approach towards 3-amino-5-hydroxycoumarin derivatives
摘要:
Aromatization of selected 3-acylamino-5,6,7,8-tetrahydro-2H-1-benzopyran-2,5-diones, yielding the corresponding 3-acylamino-5-hydroxycoumarins, was achieved by dehydrogenation with molecular oxygen in the presence of activated carbon. The use of nonpolar solvents and high temperatures was crucial for attaining satisfactory conversions. The 3-benzoylamino-5,6,7,8-tetrahydrocoumarin without a 5-keto group and the 8-oxo analogue as well as the 5-oxo-5,6,7,8-tetrahydrocoumarins containing a free 3-amino group were less efficiently aromatized..
Diels−Alder Reactions of Fused Pyran-2-ones with Maleimides: Efficient Syntheses of Benz[<i>e</i>]isoindoles and Related Systems
作者:Krištof Kranjc、Slovenko Polanc、Marijan Kočevar
DOI:10.1021/ol034852q
日期:2003.8.1
N-substituted maleimides (2a-c) leading to fused isoindole derivatives (5a-n, 7) or, in a few cases, to bridged double cycloadducts (fused bicyclo[2.2.2]octene derivatives) (6a-f) is presented. When X = CO, the first efficient, substituent-driven aromatization of an intermediary-formed cycloadduct was observed, resulting in substituted benz[e]isoindoles (5a-k). The same type of aromatization can also
Effect of Ring Size on the<i>Exo</i>/<i>Endo</i>Selectivity of a Thermal Double Cycloaddition of Fused Pyran-2-ones
作者:Kris̆tof Kranjc、Franc Perdih、Marijan Koc̆evar
DOI:10.1021/jo9011199
日期:2009.8.21
A study of an unusual effect of the size of the ring fused to 2H-pyran-2-ones on the exo/endo selectivity of a thermal double cycloaddition of N-substituted maleimides or maleic anhydride yielding bicyclo[2.2.2]octene derivatives is presented. With subtle variations of starting compounds and reaction conditions exclusively exo,exo or exo,endo products can be prepared.
Intensification of a Reaction by the Addition of a Minor Amount of Solvent: Diels-Alder Reaction of 2H-Pyran-2-ones with Alkynes
作者:Krištof Kranjc、Marijan Kočevar
DOI:10.1135/cccc20060667
日期:——
Diels-Alder transformation of substituted 3-benzoylamino-2H-pyran-2-ones 1 with a variety of alkynes 2 under microwave (MW) irradiation in a closed system can be intensified in a novel way by addition of a minor amount of butan-1-ol. When the reagents are not volatile under the used conditions, the reactions do not seem to be influenced by the addition of butan-1-ol, as demonstrated by the cycloaddition of a fused 2H-pyran-2-one 5 with N-ethylmaleimide (6) giving adduct 7.