The major reducing species operative when an equimolar proportion of AlCl3 is added over a short period of time to an ether solution of equimolar proportions of LiAlH4 and acetal or ketal

Abstract

The relative ease of hydrogenolysis of ether solutions of acetals or ketals is much greater with AlH2Cl than with AlH3. Conversion of the species [Formula: see text] one into the other is fast, and is accomplished by the addition of the appropriate quantity of AlCl3 or LiAlH4 to solutions of AlH3 or AlHCl2, respectively. Gradual addition of an equimolar proportion of AlCl3 in ether to an ether solution of equimolar proportions of LiAlH4 and acetal or ketal first forms AlH3, which is rapidly converted into AlH2Cl as more AlCl3 is added. During the time of this addition (≤ 10 min) little reduction by AlH3 takes place. Most of the reduction is done by the species AlH2Cl when the AlCl3 is completely added.