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Title: Lanthanide replacement in organic synthesis : calcium-mediated Luche-type reduction of α,β-functionalised ketones
Author: Forkel, Nina
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Complexes of alkaline earth metals (Ca, Sr, and Ba) exhibit lanthanide-like reactivity and coordination behaviour, thus it is not surprising that such alkaline earth metals are also often compared to early f-block lanthanides. Attention has been focused on calcium-catalysed reactions as calcium, the fifth most abundant element in the Earth's crust, is not only a cheaper alternative to lanthanide salts but is also less toxic, due to its high biocompatibility. As a result, the use of calcium complexes to catalyse a broad range of reactions in organic synthesis has increased tremendously over the past two decades. One such reaction where catalyst modification is suitable is the Luche reduction. The Luche reduction is one of the standard protocols for the selective reduction of α,β-unsaturated ketones to form allylic alcohols; however, the use of cerium chloride as a stoichiometric additive is not desirable for industrial-scale reactions. Successful reaction conditions for the calcium-mediated selective 1,2-reduction of challenging enones have been developed. Even the challenging substrate 2-cyclopentenone was reduced to its corresponding allylic alcohol in high 92:8 selectivity (allylic alcohol.:saturated alcohol). The developed conditions were employed to a large variety of enone substrates. Our chemistry showed high selectivity, in some cases the selectivity was even better than the selectivity obtained under classic Luche conditions. Preliminary studies have also shown that the stereoselective reduction of α,β-epoxy and α,β-aziridinyl ketones to the corresponding alcohols in the presence of calcium triflate resulted in excellent diastereoselectivity.
Supervisor: Fuchter, Matthew Sponsor: Pfizer Ltd
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available