Stereoselective and Stereospecific Triflate-Mediated Intramolecular Schmidt Reaction: Ready Access to Alkaloid Skeletons*.

The stereoselectivity and stereospecificity of the triflate-mediated intramolecular Schmidt reaction of substituted 3-(1-azidocyclohexyl)propanol derivatives leading to octahydro-1H-pyrrolo[1,2-a]azepine, the structural skeleton of several important families of alkaloids such as the Stemona alkaloids, has been examined. The reaction involves an initial intramolecular S 2 reaction between the azide moiety and the triflate affording an intermediate spirocyclic aminodiazonoium salt that undergoes the expected 1,2-shift/N -elimination followed by hydride-mediated iminium salt reduction. Remarkably, chiral alcohols are converted to the azabicyclic derivative with no or limited racemization.