Asymmetric catalysis by chiral titanium perchlorate for carbonyl-ene cyclization
摘要:
The chiral binaphthol-derived titanium perchlorate (or triflate) is shown to serve efficiently as an asymmetric catalyst for the ene cyclization of type {3, 4}exo,exo and {2, 4}exo',exo involving alpha-alkoxy aldehyde as an internal enophile to afford the 6- and 7-membered cyclic ethers in high enantiomeric purity.