Oxidative Cyclization of Unsaturated Aminoquinones. Synthesis of Quinolinoquinones. Palladium-Catalyzed Synthesis of Pyrroloindoloquinones

Article abstract of DOI:10.1021/jo00222a016

2-Allyl-3,6-diamino-5-methyl-1,4-benzoquinone (1) underwent a facile oxidative cyclization to produce quinolinoquinone 3 in the presence of a variety of oxidizing agents, including palladium(II) salts.Chloranil was the most efficient oxidizing agent and produced 3 in high yield.Under hydrolysis conditions, (hydroxyethyl)benzobis(oxazole) 4 underwent a retroaldol reaction, followed by an aldehyde amine condensation and an electrocyclic cyclization to form quinolinoquinones.In contrast, 2-allyl-3,6-bis(benzylamino)-5-methyl-1,4-benzoquinone (13) underwent smooth, palladium(II)-catalyzed cyclization to form the corresponding indoloquinone.The corresponding bis(allylamino)benzoquinone 17 underwent a similar cyclization, followed by an olefin insertion reaction to form pyrroloindoloquinones 20 and 21.