We have been exploring novel catalytic methods for the asymmetric synthesis of epoxides and have developed a new catalytic cycle for their synthesis from carbonyl compounds and diazocompounds (scheme 1).[1-3] These reactions are mediated by catalytic quantities of rhodium acetate and by catalytic quantities of dimethyl sulfide. In this catalytic cycle, the diazocompound is decomposed by rhodium acetate to a metallocarbene and this is picked up by the sulfide to give a sulfur ylide which then reacts with the aldehyde to give an epoxide and returns the sulfide back into the catalytic cycle.
Dimethyl sulfide has been substituted by chiral sulfides and non-racemic epoxides obtained.
The scope of the catalytic cycle has been probed. Substituting the aldehyde for an imine in the catalytic cycle provides aziridines in high yield and substituting the aldehyde for an enone in the catalytic cycle provides cyclopropanes in high yield. Diazoacetamides also work well in our catalytic cycle providing glycidic amides in good yield. Further details on our progress in this area will be described.
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