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Dissertation Information for Xiaohu Deng

NAME:
- Xiaohu Deng

DEGREE:
- Ph.D.

DISCIPLINE:
- Chemistry

SCHOOL:
- Emory University (USA) (2001)

ADVISORS:
- Lanny S. Liebeskind

COMMITTEE MEMBERS:
- Albert Padwa
- Dennis C. Liotta

MPACT Status: Fully Complete

Title: Part I. Synthesis of aryl or alkenyl sulfides via copper(I) mediated cross-coupling of disulfides and aryl alkenyl halides. Part II. Design of molecular switches: Novel 2,3-bisheteroaryl-quinone switch and its applications

Abstract: "A general method was developed to synthesize unsaturated sulfides via Cu(I) carboxylate mediated cross-coupling reaction between disulfides and aryl or alkenyl halides. The reaction took place under neutral conditions at relatively low temperatures. Aryl, heteroaryl and alkenyl halides (iodides or bromides) reacted with different disulfides to afford the corresponding sulfides in good to excellent yields. The reaction is stereospecific and both sides of the disulfide are utilized.

A novel molecular switch system based upon the 2,3-bisthienylquinone core was developed. It was proved that redox properties of the quinone moiety influenced the switch open-close process. Strong protic and Lewis acids have a unique effect on this system; they catalyze a ring-closing reaction to generate a switch-closed state in good yield and in large quantity. Study on the mechanism suggested that this reaction went through a bissulfonium salt intermediate. Reversion to the switch-opened state occurs with visible light.

The scope and limitations of this acid-induced ring-closing reaction were studied. It was found that the thiophenes could be replaced by other heterocycles. 2,3-bisfurylquinones, 2,3-bispyrrolylquinones and unsymmetrical 2-pyrrolyl-3-thienylnaphthoquinones all underwent the acid-induced ring-closing reaction to afford the switch-closed compounds in good yields. The influence of the ethene moiety of the 1,2-bisthienylethene switch system was also studied. For 1,2-bisthienylperfluoro-cyclopentene, acids facilitated the ring-opening reaction of the switch-closed compound to afford the switch-open compound in good yields. With 3,4-bisthienyl-3-cyclobuten-1,2-dione and 2,3-bisthienyl-2-cyclohexenone switch system, no acid-induced cyclization reactions could be observed, which suggested that aromaticity of the intermediate might play a key role.

Based on the 2,3-bisthienylquinone switch system, some interesting systems were designed. 2,3,5,6-Tetrabisthienylbenzoquinones, which incorporated two 2,3-bisthienylquinone switches in one molecule, were synthesized utilizing Stille-coupling reaction in decent yields. Some diporphyrins, linked by a 1,2-bisthienylperfluoro-cyclopentene switch or by 2,3-bisthienylquinone, were synthesized. Finally, some linear and macrocyclic compounds incorporating 2,3-bisthienylquinone switches were prepared successfully. These systems may find potential applications in electron transfer studies or novel molecular devices. Further study on the properties of these compounds is needed."

MPACT Scores for Xiaohu Deng

A = 0
C = 0
A+C = 0
T = 0
G = 0
W = 0
TD = 0
TA = 0
calculated 2008-04-07 08:14:27

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