The catalytic asymmetric aryl addition of aldehydes has attracted much attention because the chiral diaryl alcohols are important intermediates to many biologically active compounds. After the asymmetric addition of diphenylzinc to aldehyde, the mixed reagnts of Ph2Zn/Et2Zn and arylboronic acid/Et2Zn as aryl sources were developed to improve the enantioselectivity of the aryl transfer. Recently we have reported asymmetric additions of AlAr3 (THF) to aldehydes or ketones catalyzed by the titanium (IV) complexes of (R)-H8-BINOL or (S)-BINL. In this study, we develop a series of arylauminum reagents for asymmetric arylation to aldehydes. The aluminum reagents include AlPh3 (OEt2), AlPh3 (DMAP), AlPh3 (OPPh3), AlEtPh2 (DMAP), AlEtPh2 (OPPh3), and AlEt2Ph (THF). AlEt2Ph (THF) in solution is actually a mixture fo AlET3 (THF), AlEt2Ph (THF), AlEtPh2 (THF) and AlPh3 (THF). Distillation of the above mixture gave AlEt3 (THF) and AlPh3 (THF). The asymmetric additions of the aluminum reagents to 1-naphthaldehyde were studied. Results showed that the supplemental ligands have a strong influence on the reactivity and enantioselectivity in the asymmetric arylation reactions.
