[様式－学 5]
Abstract of Doctoral Thesis
Development of Regioselective Introduction of Nucleophiles toward Quinone Derivatives by New Activation Method
Doctoral Program In Advanced Life Sciences Graduate School of Life Sciences
Ritsumeikan University
かみたなか とおる Kamitanaka Tohru
Quinone-type compounds are of importance in organic chemistry as synthetic intermediates and building blocks of functional compounds, such as pharmaceuticals, agrichemicals, and chemical industries. Regarding the reactivity, many types of reactions based on the unsaturated enone structure as versatile electrophiles, especially toward various nucleophiles, have been developed. However, some chemo- and regio-selective issues at all the electrophilic ring carbons arise due to the presence of the two carbonyl functionalities and enone units in the molecules, sometimes limiting the utility of quinones themselves in organic synthesis.
To achieve the regio-specific reactions, the author now focused on quinone monoacetals (QMAs), the mono-protected quinone compounds, which can be readily prepared by oxidation of phenols developed in our laboratory using hypervalent iodine reagents, such as phenyliodine(III) diacetate (PIDA) and phnyliodine(III) bis(trifluoroacetate) (PIFA). QMAs have high electrophlicity to show various reactivities due to their bifuntionalities, that is, α,β-unsaturated carbonyl and allylacetal moieties.
However, subustitution reactions toward allylacetal moiety were rarely reported, whereas a number of addition reactions toward enone moiety were reported. This thesis describes the developement of the emerging theme for the substitution chemistry, in which the general successes are listed below.
1) First, regioselective substitution reaction of aromatic nucleophiles toward QMAs via selective activation of allylacetal moiety has been developed. This new reaction is promoted by natural source of solid acid, i.e. montmorillonite clay, in the mixture of 1,1,1,3,3,3-hexafluoroisopropanol and dichloromethane, to smoothly result in the formation of various highly oxygenated biaryls.
2) Next, synthesis of highly regiocontrolled terphenyls by repeated oxidation/arylation sequences has been established as the application of our developed reaction. Moreover, further elongated oligoarenes were synthesized utilizing this strategy.
3) Finally, the reaction mechanism was investigated by comparison of our reaction with classic SN1 reaction, that is, hydrolysis of acetals. As a result, the author has found the reactions proceed via not only SN1-type mechanism but also SN2’-type mechanism depending on the substrates an
