Regio- and Stereodivergent Allylic Reductions of Bicyclic Piperidine Enecarbamate Derivatives

The
particular nature of tetrahydro­pyrido­[4,3-e]-1,4,2-dioxazines of type 1 allows the regio-
and stereoselective obtainment of substituted N-carbamoyl
tetrahydro­pyridines by common reducing agents. A completely
novel, biologically active, bicyclic 1,3-diaza-4-oxa-[3.3.1]-nonene
scaffold can be generated by the use of lithium triethylborohydride
through unprecedented cascade syn-SN2′
reduction/carbamate reduction/cyclization reactions. The remarkable
regioselectivity switches in the allylic reduction process have been
rationalized with the aid of computational studies.