Stereoselective synthesis of 5-(1-aminoalkyl)-2-pyrrolidones and 1,7-diazaspiro[4.5]decane-2,8-diones from chiral N-tert-butanesulfinyl imines and ethyl 4-nitrobutanoate

The reaction of N-tert-butanesulfinyl imines with ethyl 4-nitrobutanoate under basic conditions produced nitro amine derivatives. The resulting β-nitroamine derivatives, isolated as a 1:1 mixture of epimers, were easily transformed into 5-(1-aminoalkyl)-2-pyrrolidones, upon reduction of the nitro group with concomitant γ-lactam formation. On the other hand, selective removal of the sulfinyl group in the β-nitroamine derivatives led to 5-nitropiperidin-2-ones in reasonable yields. From these compounds, and following a two-step process, involving conjugative addition to ethyl acrylate and final reduction of the nitro group, 1,7-diazaspiro[4.5]decane-2,8-diones were accessed in a highly stereoselective fashion.