This dissertation presents recent developments in the synthesis and chemistry of five-membered ring annulated imidazoles. Both cyclopentadienyl- and heterocycle-annulated systems are discussed. Chapter 1 introduces imidazol-2-ylidenes and their importance in chemistry: these molecules are the first stable "bottle-able" carbenes that can be used and stored as common reagents. The effect that different annulation patterns have on the carbene center is discussed. The synthesis and stability of 4,5-annulated imidazol-2-ylidenes and their metallic complexes is also presented. Chapter 2 details the synthesis and chemistry of new 4,5-cyclopentadienyl annulated imidazol-2-thiones. The chemistry of these systems allows the synthesis of different precursors of the corresponding imidazol-2-ylidenes. Chapter 3 focuses on the synthesis of 4,5-heterocycle annulated imidazoles. Precursors of the thiophene-annulated imidazol-2-ylidene and precursors of the bis(imidazol-2-ylidene) phospholes have been prepared. The bis(imidazol-2-thione)-phosphole synthesized is also the precursor of the corresponding bis(carbene) phosphorus radical. The first Nazarov cyclization involving a divinyl-phosphine derivative was also achieved.