作者:Jens Christoffers、Miriam Penning、Enno Aeissen
DOI:10.1055/s-0034-1379976
日期:——
Three regioisomeric thieno[c]azocine derivatives were prepared in six steps from bromothiophene carboxylic acids. The reaction sequence started with an esterification with isopropyl alcohol. The resulting esters were submitted to a Heck reaction with tert-butyl acrylate followed by catalytic hydrogenation. Subsequent Dieckmann condensation gave cyclopentathiophenes with a cyclic -oxo ester motif, which were -alkylated with phenacyl bromide to furnish 1,4-diketones. The latter were converted in the key step, a bismuth-catalyzed ring transformation with methylamine, yielding the racemic eight-membered ring lactams, that is, tetrahydrothieno[2,3-c]-, [3,2-c]-, and -[3,4-c]azocine derivatives in overall yields of 25%, 16% and 12%, respectively.