Highly enantioselective hetero-Diels–Alder reaction between trans-1-methoxy-2-methyl-3-trimethylsiloxybuta-1,3-diene and aldehydes catalyzed by (R)-BINOL–Ti(IV) complex

An efficient enantioselective approach to 2,5-disubstituted dihydropyrones was developed. Some easily accessible inexpensive diol ligand metal complexes were employed, and [(R)-BINOL]2–Ti(OiPr)4 complex was found to be the most effective catalyst (up to 99% yield and 99% ee in the presence of 5 mol% catalyst) for the hetero-Diels–Alder reaction between trans-1-methoxy-2-methyl-3-trimethylsiloxybuta-1,3-diene () and aldehydes. The potential and generality of this catalyst were evaluated by a variety of aldehydes including aromatic, heteroaromatic, α,β-unsaturated and aliphatic aldehydes. Based on the isolated intermediate from the reaction of benzaldehyde being confirmed by 1H, 13C NMR and HRMS data, the mechanism was proposed as a Mukaiyama aldol pathway.