Cobalt mediated cyclotrimerization of alkyne and isocyanate to form 2-pyridones new linkage chemistry for RNA mediated nanoparticle growth on gold surface /

by 1976- Wu, Tong

WU, TONG. Cobalt Mediated Cyclotrimerization of Alkyne and Isocyanate to Form 2- Pyridones; New Linkage Chemistry for RNA Mediated Nanoparticle Growth on Gold Surface. (Under the direction of Professor Bruce E. Eaton). Cobalt (I) mediated cyclotrimerization is a powerful synthesis methodology to construct six member carbocyclic and heterocyclic aromatic rings. A new cobalt (I) catalyst, CpCF3CoCOD, was synthesized successfully. The X-ray crystal structure analysis revealed special structure features, which could be feasible to the associative Cp ring slippage mechanism. Examination of cyclotrimerization of alkyne showed CpCF3CoCOD was a very active catalyst. Kinetic data indicated that the reaction rate shows a first order dependence on the concentration of alkyne. Cyclotrimerization between alkyne and isocyanate has been investigated with new cobalt catalyst, CpCF3CoCOD. It was found that 2-pyridones could be formed under mild experimental conditions with excellent yield and chemospecificity. The yield and product distribution depends greatly on the substituents of alkyne and isocyanate. Cylcotrimerizing diyne and isocynante gave moderate to good yields. The yield of diyne conversion to 2-pyridones was controlled by the Thorpe – Ingold effect. An associative Cp ring slippage mechanism has been proposed for cyclotrimerization of alkyne and isocyanate. In order to maintain RNA’s folded structure to afford shape-controlled nanoparticles, it was of interest to test a linker to connect RNA to the gold surface. Two linker strategies were examined to achieve this goal. One strategy assembles linker onto gold surface firstly, and then 5’-phosphorothioate-modified RNA will introduce to couple with the linker. The other strategy uses chemical or enzymatic methods to bind the linker with RNA molecules firstly; then, Linker and RNA molecule were introduced onto gold surface as a single molecule. The synthetic routes for both linkers were established. Gold slides were prepared according to these strategies and were examined by SEM. In both cases, well-shaped hexagonal Pd nanoparticles were observed. The second strategy provided cleaner background. SEM images also showed that particle density appeared dependence on RNA concentration. Cobalt Mediated Cyclotrimerization of Alkyne and Isocyanate to Form 2-Pyridones; New Linkage Chemistry for RNA Mediated Nanoparticle Growth on Gold Surface by Tong Wu A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirement for the Degree of Doctor of Philosophy Chemistry Raleigh 2006 Approved By: __________________________ Bruce E. Eaton Chair of Advisory Committee __________________________ Daniel L. Feldheim __________________________ __________________________ T. Brent Gunnoe Bruce M. Novak