Abstract
A new route to the title benzo-fused angular tricyclic amides 3,3a,4,5-tetrahydropyrrolo- and 2,3,4,4a,5,6-hexahydro-1H-pyrido[1,2-a]quinolin-1-ones is reported from 1-(tert-butyl) 6-ethyl 3-oxohexanedioate and 1-(tert-butyl) 7-ethyl 3-oxoheptanedioate. Alkylation of these β-keto diesters with a series of 2-nitrobenzyl bromides followed by acid hydrolysis and decarboxylation gives ethyl 6-(2-nitrophenyl)-4-oxohexanoates and ethyl 7-(2-nitrophenyl)-5-oxoheptanoates, respectively. Reductive amination under hydrogenation conditions followed by ester hydrolysis and condensative ring closure affords the final lactam products. The reactions proceed cleanly and only two chromatographic purifications are required.
Key words
benzo-fused lactams - alkylation–decarboxylation - β-keto diesters - reductive amination - ester hydrolysis - lactamization
