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  4. The Application of Radical Cyclization Reactions of Carbonyl Compounds and the Study of Controlled Living Radical Polymerizations
 
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The Application of Radical Cyclization Reactions of Carbonyl Compounds and the Study of Controlled Living Radical Polymerizations

Date Issued
2007
Date
2007
Author(s)
Chang, Che-Chien
DOI
en-US
URI
http://ntur.lib.ntu.edu.tw//handle/246246/51858
Abstract
ENGLSIH ABSTRACT This thesis is divided into two parts, one is the application of radical cyclization reactions of carbonyl compounds, and the other is the study of controlled living radical polymerizations. In the first chapter, the intramolecular cyclization of the α-sulfenyl radical cyclization with acylsilane went through the cyclization-rearrangement-fragmentation pathway to afford silyl enol ethers. Thiophenol, generated from the reaction cycle, enhanced the efficiency of hydrogen abstraction. The best result of the product ratio (silyl enol ethers/ reduction products = 2/1, determined by NMR integration) was obtained by the addition of allyltributyltin as an additive. Unfortunately, α-sulfonyl radical did not cyclize to acylsilanes. Second, we have developed a procedure that could convert carbohydrates to functionalized carbocycles. A successful method to construct α-oxygenated carbohydrate-derived acylsilanes was also explored. Three different acylsilanes, derived from arabinose, lyxose, and ribose were converted to functionalized silyloxy carbocycles. These results are the first examples of radical cyclization reactions of acyclic sugars, which could give one additional hydroxyl group or silylated hydroxyl group on the newly formed carbocyclic rings. 6-Exo cyclization reaction of mannose-derived acylsilane was not successful due to the formation of a particularly stable radical intermediate stabilized by the captodative effect. The cyclization precursor, bearing α-oxygenated tin-xanthate moiety, was also prepared in order to study the 1,3-stannyl shift in carbohydrate system. α-Oxygenated tin-xanthate moiety is a labile functional group during the preparation. The six-membered ring α-acylamino radical precursor accessed from a monosaccharide and a simple saturated aliphatic acylsilane were prepared. Tin-mediated cyclization reaction to construct indolizidinone is not so efficient. Very low yield was obtained. In the second part of this thesis, the styryl-TEMPO-mediated styrene polymerization can be accelerated upon using efficient alkoxyamines as additives. For additives with equilibrium constants that are 3 orders of magnitude larger than K of styryl-TEMPO, an increase of the conversion by about a factor of 2 can be achieved. Good results can be obtained with only 25% of the alkoxyamine additive with respect to styryl-TEMPO. The results are further supported by numerical simulations. We have also showed that the ring-enlarged alkoxyamine 99 is a more efficient initiator/regulator for controlled living radical polymerization of styrene than its lower homologue 84. The equilibrium constant K of 99 is about 3 times larger as compared to the K-value of 84, clearly documenting the benefit of the ring-enlargement by the insertion of an NH moiety.
Subjects
自由基環合反應
活性自由基聚合反應
Radical Cyclization Reactions
Controlled Living Radical Polymerizations
Type
thesis
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