Aromatization Of Nitrogen-Containing Heterocycles And Its Application In Total Syntheses Of Several β-Carboline Alkaloids

This dissertation discussed the aromatization of3,4-dihydro-β-carbolines,1,2,3,4-tetrahydro-β-carbolines, imidazolines, and1,4,5,6-tetrahydro-pyrimidines. Futhermore, total syntheses of several β-carboline alkaloids by applying the above aromatization method have also been performed. It contains four parts as described below:(1) Aromatization of3,4-dihydro-β-carbolines and1,2,3,4-tetrahydro-β-carbolines:3,4-Dihydro-β-carbolines with electron-withdrawing substituted groups were converted into corresponding P-carbolines in76-93%yields via aerobic oxidative aromatization with DBU as the base in DMSO at room temperature. In contrast,3,4-dihydro-p-carbolines without electron-withdrawing substituted groups were converted into corresponding β-carbolines in68-95%yields via copper-catalyzed aerobic oxidative aromatization with DBU as the base in DMSO at25℃or45℃. Specially, aromatization of1,2,3,4-tetrahydro-β-carbolines was also studied.1,2,3,4-Tetrahydro-β-carbolines were converted into corresponding-β-carbolines in66-95%yields via copper-catalyzed aerobic oxidative aromatization with DBU as the base in DMSO at25℃or45℃.(2) Aromatization of imidazolines:Imidazolines were converted into corresponding imidazoles in71-96%yields via copper-catalyzed aerobic oxidative aromatization with DBU as the base in DMF at room temperature.(3) Aromatization of1,4,5,6-tetrahydro-pyrimidines:An efficient, mild, benign and practical method for the conversion of N-tosyl-1,4,5,6-tetrahydro-pyrimidines into pyrimidines was studied. N-Tosyl-1,4,5,6-tetrahydro-pyrimidines were prepared and treated with1.5equivalents of sodium hydroxide in dimethyl sulfoxide (DMSO) under air at60℃. A total of twenty four desired pyrimidines were obtained in70-95%yields via cascade β-elimination and aromatization.(4) Application of aromatization of3,4-dihydro-β-carbolines and1,2,3,4-tetrahydro-β-carbolines in total syntheses of β-carboline alkaloids such as eudistomins Y1-Y7, cordysinins C&D, eudistomin U, eudistomin I, and alangiobussinine:The first total synthesis of eudistomin Y7and novel total syntheses of eudistomins Yi-Ye were described. An efficient room-temperature conversion of1-benzyl-3,4-dihydro-β-carbolines into1-benzoyl-β-...