Highly Enantioselective Conjugate Addition of AlMe_3 to Linear Aliphatic Enones by a Designed Catalyst

摘要

2-Hydroxy-2'-alkylthio-1,1'-binaphthyl compounds are catalytic promoters of teh 1,4-addition of AlMe_3 to linear aliphatic enones in THF at - 40 to -48 deg C in the presence of [Cu(MeCN)_4]BF_4. At ligand loadings of 5-20 mol%, enantioselectivities of 80-93% are realised for most substrates. To attain these values, the use of highly pure AlMe_3 is mandatory. The presence of methylalumoxane (MAO), derived by hydrolysis, leads to reduced enantioselectivity and a conjugate addition product.