Journal of Organic Chemistry vol:58 issue:3 pages:690-695
This report describes the synthesis of the title compound 7 and its conversion into 2,7-substituted octahydro-2H-pyrido[1,2-a]pyrazines, i.e., bicyclic analogues of the monocyclic piperazine drug lidoflazine. The synthesis of 7 is based on a 3-fold amino substitution of methyl 6-chlor-5-oxohexanoate (12), initiated by displacement of chlorine with N-benzyl-N'-trityl-1,2-ethanediamine. The required trielectrophile 12 was prepared readily from commercially available diethyl 2-acetyl-glutarate. The 7-position of compound 7 was functionalized through reaction of the lactam anion with benzophenone electrophiles. Further elaboration into the target compounds 8-10 involved dehydration, reduction of the lactam group, and different modes of N-debenzylation. Conformational aspects for lactam compounds 17 and 18 and the modes of ring fusion for the diastereomeric amines 9 and 10 were examined by using proton NMR and infrared spectroscopy.