Thiamine is an essential vitamin that possesses the important ability to form acyl anion equivalents for C-C bond formation. This ability is conserved even in the absence of an enzyme and a variety of other carbene precursors have been found to catalyze transformations similar to their in vivo counterparts. This catalytic manifold is best exemplified by the benzoin and Stetter reactions generating α-hydroxyketones and 1,4-dicarbonyl products, respectively. Severe limitations to the scope of these reactions have hindered their broad application. Our progress in improving the scope as well as application to the synthesis of two natural products will be presented. In parallel, we have also embarked on the preparation of molecules of fundamental interest. One class of such compounds is represented by 10-membered hydrocarbons bearing fused cyclopropanes. Although nominally aromatic, their properties and even their existence under ambient conditions has remained unknown for nearly three decades. Our recent success in synthesizing some of these intriguing compounds will be discussed.