The preparation of a 10-membered ring macrolactone by selective ozonolysis and the role of the dihydropyran-substituent on the MCPBA-oxidation reaction profile of beta-lapachone phenazines

The benzophenazine from beta-lapachone was submitted to ozonolysis under conditions that selectively furnished the corresponding rigid macrocyclic lactone 7,7-dimethyl-7,8,9,10-tetrahydro-5H-benzo[3,4]oxecino[5,6-b]quinoxaline-5,10-dione in an yield of 52%. The effect of substituents located at the dihydropyrane moiety of the phenazines, namely C2'-OH, C2'-Br and C2'-I, in the oxidation with MCPBA, was also investigated.