Catalysis via Transition Metal-Mediated Carbene Transfer to Sulfides

2 Catalysis via Transition Metal-Mediated Carbene Transfer to Sulfides 

However, attempts to use sulfide 18b in this process gave the desired epoxides in low yields, which may be resulted from the decomposition of the catalyst under these conditions. The more stable sulfide 19 proved to be the catalyst of choice for this protocol it can be prepared in four steps from camphor sulfonyl chloride. The combination of lmol% Rh2(OAc)4 and 5mol% sulfide can promote the epoxidation reaction of a range of aromatic and heteroaromatic aldehydes with high enanhoselectivity (up to 94% ee), with the exception of pyridine carboxalde-hyde [31]. 

The sulfide-catalyzed enantioselective epoxidation reaction is the most extensively studied transformation in ylide catalysis, and two ylide generation methods (aUcylation/deprotonation and carbene transfer) have been developed. Compared with conventional methods for epoxidation via oxygen transfer to the carbon-carbon double bond, such as the Sharpless epoxidation, Jacobsen-Katsuki epoxidation, and Shi epoxidation, the yhde approach can be regarded as an alkyUdene transfer reaction to carbonyl groups (C=0), providing a different retrosynthetic analysis for the construction of epoxides. In particular, in the synthesis of vinyl epoxides, the ylide route has priority over conventional oxidation methods, since the issue of regjoselectivity in the epoxidation of dienes will not be present [32]. 

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