title: A way to avoid using precious metals: the application of high-surface activated carbon for the synthesis of isoindoles via the Diels-Alder reaction of 2H-pyran-2-ones.
abstract: The application of activated carbon (Darco KB) for the acceleration and direction of the transformation of various 2H-pyran-2-ones with N-substituted maleimides toward isoindole derivatives through the reaction sequence cycloaddition/elimination/dehydrogenation is described. In this reaction, the catalyst mainly influences the dehydrogenation step, which is essential to avoid the formation of bicyclo[2.2.2]octenes as the other possible products. We found that the combination of Darco KB, as the metal-free catalyst, and decalin, as the solvent in a closed vessel, represents the most successful conditions. A comparison of the effect of various dehydrogenation catalysts and reaction conditions is also presented. In addition, we have proven that the aromatization occurs via a hydrogen transfer from the cyclohexadiene intermediate to the maleimide derivative (therefore producing succinimides). This transfer is facilitated by the active surface of the heterogeneous carbon-based catalyst.
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana, Slovenia.
authors.forename: Marko
authors.initials: M
authors.lastname: Krivec
authors.forename: Martin
authors.initials: M
authors.lastname: Gazvoda
authors.forename: Krištof
authors.initials: K
authors.lastname: Kranjc
authors.forename: Slovenko
authors.initials: S
authors.lastname: Polanc
authors.forename: Marijan
authors.initials: M
authors.lastname: Kočevar
mesh_terms: D002244:Carbon / Q000737:chemistry*; D003500:Cyclization; D054833:Isoindoles / Q000138:chemical synthesis* / Q000737:chemistry*; D008670:Metals / Q000737:chemistry*; D015394:Molecular Structure; D011753:Pyrones / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D054833:Isoindoles; D008670:Metals; D011753:Pyrones; D002244:Carbon