Synthesis of Dihydro Diols and Epoxides of Benzoquinoline

Article abstract of DOI:10.1021/jo00368a001

The syntheses of two non-K-region trans dihydro diols 21 and 30 and three diol epoxides 23, 26, and 36 of benzoquinoline (1) are described.The dihydro diols 21 and 30 were obtained from 7,8,9,10-tetrahydrobenzoquinoline (3) via the trans-7,8-diacetoxy-7,8,9,10-tetrahydrobenzoquinoline (14) and its trans 9,10-diacetoxy isomer (15) by benzylic bromination followed by dehydrobromination.The trans tetrahydro diacetates 14 and 15 were obtained through the alkenes 6 and 7 and their epoxide derivatives 10 and 11.The oxidation of dihydro diol 21 with m-CPBA failed to produce anti diol epoxide 2.The presence of N-oxides 22 and 23 in the reaction mixture indicated that the oxidation preferentially occurred at nitrogen of 21.On the other hand, cis diol epoxide 26 was obtained by treatment of diacetate 26 with NBA followed by cyclization with Amberlite resin and hydrolysis of the resulting diacetoxy epoxide 25.Reaction of 29a with NBA produced a mixture of two stereoisomeric bromohydrins 32 and 33 which did not cyclize with Amberlite resin.Therefore, tetra-n-butylammonium hydrogen sulfate was employed as ring closing agent. 1H NMR, UV, and mass spectra of benzoquinoline derivatives are reported.