Figure 2: Regioselective and enantiospecific S–M cross-coupling of heterocyclic allylic boronates 3 and 4.

By making use of antipodes of the chiral ligand TANIAPHOS in the catalytic enantioselective borylation of achiral enol triflates 1 and 2, both enantiomers of 3 and 4 can be obtained in high selectivity. On a catalyst-controlled regiodivergent and stereospecific cross-coupling process, both 2- and 4-substituted regioisomeric products can be formed and isolated independently. The entire process thus lends access to all four possible isomeric piperidine and pyran isomers.