Synthesis of α-carbolines and β-carbolinones via intramolecular Diels-Alder reactions of 2(1 H)-pyrazinones

2(1 H)-Pyrazinones bearing a X-( o-C 6H 4)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...

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Bibliographic Details
Published in:Tetrahedron 1998-10, Vol.54 (43), p.13211-13226
Main Authors: Tahri, Abdellah, Buysens, Kris J., Van der Eycken, Erik V., Vandenberghe, Didier M., Hoornaert, Georges J.
Format: Article
Language:English
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Summary:2(1 H)-Pyrazinones bearing a X-( o-C 6H 4)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. Thermolysis of precursors 2 in different solvents gives α-carbolines 3 and β-carbolinones 4.
ISSN:0040-4020
1464-5416
DOI:10.1016/S0040-4020(98)00802-3