Jacobsens Catalyst Family

During the usual course of catalyst development several closely related candidates are synthesized and evaluated. In this way certain structural changes with beneficial effect on catalysis can be identified, and incorporated in the final catalyst 

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Figure 12.12 Selected examples fr om the Jacobsen catalyst family.

The synthesis of the tetrasubstituted dihydroquinoline portion of siomycin Di, which belongs to the thiostrepton family of peptide antibiotics, was achieved in the laboratory of K. Hashimoto. The Jacobsen epoxidation was utilized to introduce the epoxide enantioselectively at the C7-C8 position. The olefin was treated with 5 mol% of Jacobsen s manganese(lll)-salen complex (R =f-Bu) and 4% aqueous NaOCI solution in dichloromethane. To enhance the catalyst turnover, 50 mol% of 4-phenylpyridine-A/-oxide was added to the reaction mixture. The desired epoxide was obtained in 43% yield and with 91% ee. 

In 2004 Can Li published a seminal review in which the weak interactions between the surface of the support and the heterogenized catalyst were analyzed with respect to their influence on the transition state of the enantioselective transformation, exploiting the concept of the confinement effect. " A series of examples were considered including a variety of epoxidation systems such as the Sharpless Ti catalyst for the epoxidation of allylic alcohols or the Jacobsen family of catalysts for the epoxidation of simple alkenes, all prepared by grafting, encapsulation and... 

Eric N. Jacobsen of Harvard University has devised a family of catalysts for the enantioselective Pictet-Spengler reaction of tryptamine 21. He has now (Organic Lett. 2008, 10, 745) used this approach to prepare the triene 22 in 94% ee. The Diels-Alder cyclization of 22 proceeded with high diastereocontrol to give 23, the immediate precursor of (-)-yohimbine 24. 

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