The palladium catalyzed multicomponent synthesis of imidazoles and imidazole-containing [pi]-conjugated polymers /

The primary goal of this study is to develop novel metal catalyzed multicomponent reaction methods to generate imidazoles and their derivatives. This is directed towards the assembly of poly-substituted imidazoles, imidazolones and imidazole-containing pi-conjugated polymers. These products are generated in one-pot from such basic components as imines, acid chlorides, carbon monoxide, and/or organostannanes, via the use of palladium catalysis.In Chapter 2, the design of a new palladium catalyzed synthesis of highly substituted imidazoles from imines and acid chlorides is described. This reaction involves the palladium catalyzed generation of 1, 3-oxazolium-5-oxides (Munchnones); which are trapped with N-tosyl substituted imines via a 1, 3 dipolar cycloaddition reaction to form the final products. Overall, this provides a one step method to assemble imidazoles from imines and acid chlorides with excellent regiochemical control. The versatility of this process is demonstrated by the assembly of diversely substituted imidazoles, including those with aryl, alkyl, heterocyclic and vinyl substituents.Chapter 3 describes a new, palladium catalyzed, five component coupling of imines, chloroformates, organotin reagents, carbon monoxide and ammonium acetate to form imidazolones. The key step in this process is the efficient formation of ketocarbamates via the carbonylative cross coupling type reaction of imines, chloroformates and organostannanes. These products can be easily converted into imidazolones via a cyclocondensation with ammonium acetate.The synthesis of pi-conjugated imidazole-containing polymers is described in Chapter 4. This process is designed based upon our previous studies on palladium catalyzed multicomponent synthesis of imidazoles, developed in Chapter 2. It is shown that bifunctional monomers such as di-imines, di-acid chlorides and di-N-tosylimines can be coupled together to assemble pi-conjugated imidazole-containing oligomers and polymers utilizing this same palladium catalyzed reaction. This approach was used to create a novel library of conjugated imidazole polymers. By modifying the substituents on the polymer structures, the UV-vis absorbance and fluorescence excitation/emission spectra of these compounds are varied over a range of 150 nm.In Chapter 5, the palladium catalyzed multicomponent polymerization is discussed in more detail. This includes the analysis of the end groups on the polymer backbone, as well as mechanistic studies into how the polymerization is terminated. These results suggest that the sulfinate anion liberated upon N-tosylimine cycloaddition may be non-innocent in this polymerization, and its presence could lead to termination of the growing polymer chain