A highly chemo- and stereo-selective cleavage of acetals derived from (−)(2R,4R)-2,4-pentanediol with organoaluminum and organotitanium reagents has been demonstrated. The reactions proceed under mild conditions with excellent yields and high chemoselectivities to give, after removal of the auxiliary, chiral alcohols of high enantiomeric purities.
Reductive cleavages of homochiral acetalsusing Lewis acid-hydride systems and of alkynyl acetalsusingorganoaluminumreagents are described. Stereochemical outcomes are found to be the opposite compared with our previous results on the aluminum hydride reduction of the acetal.