Cycloaddition Routes to Azaanthraquinone Derivatives. 1. Use of Azadienophiles

Article abstract of DOI:10.1021/jo00361a014

The mono- and diazanaphthoquinones underwent facile cycloaddition with cyclic and alicyclic dienes, and in the majority of these cycloadditions the initial 1:1-cycloadducts or their tautomers and intermediate products formed in the oxidation procedure leading to the final azaanthraquinones were isolated.Quinoline-5,8-dione and 1-methoxy-1,3-cyclohexadiene gave the 8-methoxy isomer in an essentially regiospecific cycloaddition; isoquinoline-5,8-dione, however, gave both the 5- and 8-methoxy isomers in a 2.8:1 ratio.These structural assignments were verified by alternative syntheses of the possible isomers using heteroatom-directed lithiation procedures.