Preparation of Z-α,β-unsaturated diazoketones from aldehydes. Application in the construction of substituted dihydropyridin-3-ones.

The stereoselective preparation of α,β-unsaturated diazoketones with Z geometry is described from aldehydes and a new olefination reagent. When prepared from amino aldehydes, these diazoketones could be converted to substituted dihydropyridin-3-ones in just one step, after an intramolecular N-H insertion reaction. The straightforward synthesis of a natural trihydroxylated piperidine demonstrates the utility of these unsaturated diazoketones for the rapid construction of piperidines.