Nucleophilic cleavages of acetals using organotitanium reagents. A new synthesis of chiral alcohols

A highly chemo- and stereoselective cleavage of acetals derived from (?)-(2R,4R)-2,4-pentanediol with organotitanium reagents has been demonstrated. The reaction proceeds under mild conditions in excellent yield and high chemoselectivity to give, after removal of auxiliary, the chiral alcohols of high enantiopurities. In addition, complexation of chiral acetals and TiCl₄ followed by treatment with n-butyllithium also results in formation of the corresponding $\text{n}$-butylated alcohols with high stereoselectivity.