Abstract
A series of chiral oxidovanadium(V) methoxides were prepared from 3-disubstituted (included methoxy, methyl, and phenyl, etc.) aromatic substituted-5-nitro-N-salicylidene L-tert-butylglycinates and vanadyl sulfate in oxygen-saturated methanol. These complexes serve as highly enantioselective catalysts for asymmetric 1,4-conjugate addition. We used benzyl 2-oxocyclopentanecarboxylate as a major Michael donor. Besides, we also used Benzyl 2-oxo-1-indanecarboxylate, which is rarely mentioned in literature, as a Michael donor. For Michael acceptor, we used methyl vinyl ketone, cyclohexanyl vinyl ketone, tetraethyl ethylidene bisphosphonate of phosphate compounds, methyl ethylnl ketone and phenyl ethylnl ketone of alkynyl ketones, vinyl phenyl sulfone and vinyl phenyl selenone etc. The best results were obtained from 2-oxocyclopentanecarboxylate and methyl vinyl ketone, when using 1a as a chiral catalyst for asymmetric 1,4-conjugated addition, affording the Michael adduct in 75% yields and up to 82% ee.