216104-96-0Relevant academic research and scientific papers
Divergent pathways in the intramolecular Diels-Alder reaction of 2(1H)- pyrazinones substituted at the 3-position with a phenylalkyne containing side chain
Tahri,De Borggraeve,Buysens,Van Meervelt,Compernolle,Hoornaert
, p. 14675 - 14684 (2007/10/03)
2(1H)-Pyrazinones bearing an X-(o-C6H4)-C≡C-R moiety (X=O or NH; R=H, Ph or TMS) at position 3 were subjected to intramolecular Diels-Alder reaction. For the ether compounds (X=O) cycloaddition-elimination occurred readily to produce either benzofuro[2,3-c]pyridin-1(2-H)-ones or benzofuro[2,3-b]pyridines. For the aniline derivatives (X=NH, R=H or TMS) thermolysis in acetic anhydride resulted in a similar product distribution of β-carbolinones and α-carbolines which, however, differed from that obtained previously in refluxing tetrahydronaphthalene. This result is explained by the cycloaddition proceeding from the aniline NH-acetylated precursor. However, the aniline derivatives with Ph as the acetylenic end group (X=NH, R=Ph) reacted via a divergent pathway to produce N-(2-oxopyrazin-3-yl)-2-Ph- substituted indoles.
Synthesis of α-carbolines and β-carbolinones via intramolecular Diels- Alder reactions of 2(1H)-pyrazinones
Tahri, Abdellah,Buysens, Kris J.,Van Der Eycken, Erik V.,Vandenberghe, Didier M.,Hoornaert, Georges J.
, p. 13211 - 13226 (2007/10/03)
2(1H)-Pyrazinones bearing a X-(o-C6H4)-C≡C-R moiety (X=NH, NAc) are shown to undergo an intramolecular cycloaddition-elimination reaction on thermolysis in refluxing bromobenzene yielding α-carbolines or β- carbolinones. The product distribution depends strongly on the substitution pattern of the pyrazinone precursors and the solvent used for thermolysis. A high yield and selective formation of β-carbolinones is possible when heating in tetrahydronaphthalene at reflux. Use of acetic anhydride as solvent facilitated the reaction and made it possible to realise a carbolin(on)e unaccessible by thermolysis in the previously mentioned solvents.
