Organocerium additions to chiral α,α-dialkoxy hydrazones: Asymmetric synthesis of JV-protected a-amino acetals and α-amino aldehydes

A general and selective procedure for the diastereoselective additions of organocerium reagents to chiral α,α-dialkoxy hydrazones has been developed. The best reagent combination-involved a 6:1 composition of RMet to CeCl3. Excellent yields and high selectivities were obtained after trapping as the uo-butyl carbamates. Lithium-ammonia cleavage of the N-N bond followed by hydrolysis with TMSI afforded the protected ot-amino aldehydes.