MODERATE ENANTIOSELECTIVITY PROMOTED BY CYCLODEXTRINS IN THE ZN-BARBIER ALLYLATION REACTION OF ALDEHYDES IN AQUEOUS-MEDIUM

The effects exerted by native and trimethylated (-cyclodextrins in the Zn-Barbier allylation reaction of aldehydes in aqueous solution has b een studied. The rates of conversion were, generally, depressed in the presence of the cyclodextrins, especially TMCD, but the chemical yiel ds of the products were very satisfactory, in all cases. Moderate enan tioselectivity effects were also obtained in the presence of TMCD, whe reas native (CD showed to be practically inactive. The results can be rationalised in terms of formation of inclusion complexes between the substrates and the CDs and of their interaction with the surface of th e metal.