Diastereoselective Zinc-Catalyzed Conjugate Addition of Alkynes
摘要:
[GRAPHICS]The conjugate addition of in situ generated zinc alkynylides is reported. The use of chiral, ephedrine derived acceptors provides access to enantiomerically enriched beta-alkynyl acids in good yields.
Asymmetric Synthesis Based on (2<i>R</i>,3<i>S</i>)-3,4-Dimethyl-2-phenylperhydro-1,4-oxazepine-5,7-dione. Synthesis of Highly Optically Active β-Substituted Alkanoic Acids
A general method was worked out for the preparation of highly optically pure β-substituted alkanoic acids from aldehydes with use of (2R,3S)-6-alkylidene-3,4-dimethyl-2-phenylperhydro-1,4-oxazepine-5,7-diones(2) as key intermediates. Oxazepines(2) were prepared in high yields by treating aldehydes with (2R,3S)-3,4-dimethyl-2-phenylperhydro-1,4-oxazepine-5,7-dione(1) in the presence of titanium tetrachloride