Regio- and Diastereoselective Cross-Dehydrogenative Coupling of Tetrahydropyridines with 1,3-Dicarbonyl Compounds.

A regio- and diastereoselective cross-dehydrogenative coupling of N-carbamoyl tetrahydropyridines with a variety of 1,3-dicarbonyl compounds is described. The method exhibits good functional group tolerance, diastereoselectively generating cis-2,6- or cis-2,4-substituted tetrahydropyridines by using different types of 1,3-dicarbonyls. Moreover, a two-step sequence involving diastereoselective cross-dehydrogenative coupling followed by epimerization was also developed, allowing facile access to trans-2,6-substituted tetrahydropyridines as single isomers. Applications in natural product synthesis and divergent analogue preparation were further demonstrated.