| Summary: | 碩士 === 國立東華大學 === 化學系 === 95 === α-Phenylseleno ketones are of considerable importance in synthetic chemistry. They have been commonly used as the substrates for the preparation of α,β-unsaturated carbonyl compounds via an oxidative elimination operation. Besides, many of them have been applied as the elaborated precursors in promoting different radical-mediated processes. In addition to their synthetic versatility, a specific series of α-phenylseleno ketones have been shown to exhibit interesting glutathione peroxidase-like antioxidant properties, indicating that these compounds may potentially serve as anticancer, antiviral, antihypertensive, anti-inflammatory, and immunosuppressive agents.
While numerous methods for the preparation of α-phenylseleno ketones are available at the present time, the efficient control over the regioselectivity yet represents as a frequent problem for those unsymmetrical ketones when the α and the α′carbons to a ketone carbonyl are both susceptible to selenenylation. In this thesis, we describe an efficient procedure for the regiocontrolled generation of α-phenylseleno ketones from the corresponding α-cyano ketones, utilizing the lithium naphthalenide induced reductive selenenylation as a key operation. Our approach is based on the reductive decyanation of α-cyano ketones promoted by LN, followed by the trap of the resulting enolates with phenylselenyl bromide. Through this method, a great variety of α-phenylseleno ketones was prepared in good to excellent yields with the complete control of the regioselectivity. In addition, we also observed that the α-phenylseleno ketones thus formed in situ, without isolation, could be directly converted into the corresponding α,β-unsaturated ketones upon the one-pot treatment with hydrogen peroxide with high regio- and stereoselectivity in respect to the formation of C=C double bond. The preferential formation of the exo double bond in some cases was rationalized on the basis of the lithium coordination.
In addition, the application of the aforementioned reductive selenenylation procedure into the synthesis of α,α-dialkyl α-phenylseleno acetates also met with a great success. The results from the study will be also described in this thesis.
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