Diels-Alder Reactions of 7-Azalumazines. Synthesis of Condensed Lumazines and 8-Deazalumazines

Article abstract of DOI:10.1021/jo00250a029

7-Azalumazines tethered at the C6 position with a series of dienophilic side chains undergo intramolecular Diels-Alder reactions to provide 6,7-annulated lumazines and 8-deazalumazines.The rates of these cycloaddition reactions are markedly faster than for previously reported cycloadditions of isomeric C7-tethered 6-azalumazines.On the other hand, 7-azalumazines do not undergo intermolecular Diels-Alder reactions with enamine dienophiles, whereas under identical conditions, 6-azalumazines react readily.Reasons for this striking reversal in reactivity observed for inter- and intramolecular Diels-Alder reactions of 6- vs 7-azalumazines are discussed.