New optically active aminoalcohols have been prepared from CeCl3-activated (+)-camphor and (-)-fenchone and N-functionalized organolithium compounds. The aminoalcohols obtained catalyze the addition of diethylzinc to benzaldehyde in high yields and enantioselectivities up to 64%. (~) 1997 Elsevier Science Ltd
The synthesis of optically active aminoalcohols and their application as catalysts for enantioselective addition reactions of dialkylzinc compounds to aldehydes has been a topic of increased interest in recent years I . Noyori and co-workers have demonstrated one of the most effective ligands as catalysts, (-)-3-exo-(dimethylamino)isoborneol (DAIB), and have suggested an explanation for its catalytic activity and efficiency 2. The synthesis and application of some other camphor derived aminoalcohols have also been described 3,4 showing the potential importance of the camphor skeleton as a source of chiral information.
The addition of organometallic reagents to (+)-(1R)-camphor 1 and (-)-lR-fenchone 2 has been the key step in our investigations concerning the synthesis of optically active alcohols 5a,b, diols 5c,d and epoxyalcohols 5e. In most of the cases the use of highly active anhydrous CeC13, prepared by an improved procedure, was necessary for the activation of these ketones, providing an excellent addition of a variety of organometallics 5a,6. With the addition of N,N-dimethylaminopropyl lithium 3 to 1 and 2 we demonstrated 5a a useful one-step synthetic procedure for the preparation of aminoalcohols 8 and 13 (Scheme 1). In this paper we report on the preparation of new chiral aminoalcohols via the addition