Synthesis of Indeno[1,2-d]azepine Derivatives

Abstract

Abstract 4-Ethoxyindeno[1,2-d]azepine(18) and 10-bromo-4-ethoxyindeno[1,2-d]azepine were prepared by O-ethylation of indeno[1,2-d]azepin-4-ol(12ab) and 10-bromoindeno[1,2-d]azepin-4-ol(13ab) with Et3OBF4 in 62 and 69% yields, respectively. 12ab was obtained by bromination of 1,2,3,4,5,10-hexahydro-4-indeno[1,2-d]azepine(3) or 1,2,3,4-tetrahydroindeno[1,2-d]azepin-4-one with NBS, and subsequent dehydrobromination of the corresponding bromide formed in situ on basic alumina in 10% yield. When the bromination time was over 20 h, only 13ab was isolated in 20% yield. Direct dehydrogenation of 3 with DDQ gave 10-chloroindeno[1,2-d]azepin-4-ol in 27% yield. The NMR and electronic spectra of 18 indicated the presence of a fully conjugated 14-pi ring system in it. We also investigated the possibility for dehydrogenation of 3-ethoxycarbonyl-1,2,3,4,5,5a,10,10a-octahydroindeno [1,2-d] azepin-10-one.