Synthesis and Reactions of Bicyclo[1.1.0]butanes

This dissertation describes methods for the synthesis of bicyclo[1.1.0]butanes and their reactions. The bicyclo[1.1.0]butyl skeleton was first assembled by intramolecular, amide directed Simmons-Smith cyclopropanation of propargyl amides and cyclopropenes. However, a more general approach applicable to the synthesis of amines, alcohol, esters, and amides was developed. This method is based on the generation of bicyclo[1.1.0]butyllithium from gem-dibromocyclopropanes via sequential transmetallation reactions with alkyllithium reagents and addition to electrophilic acceptors.Studies on the reaction of bicyclo[1.1.0]butanes were focused on thermal and metal-catalyzed transformations. Bicyclo[1.1.0]butanes activated by an aromatic group underwent highly chemo- and diastereoselective intramolecular pericyclic reactions under mild conditions. The outcome of these processes was controlled by the selection of the allylating reagents, and N-allyl amides gave exclusively formal ene products. On the other hand, cinnamyl amides participated in an intramolecular cycloaddition reaction. The postulated presence of radical in the mechanism of these reactions was supported by chemical and spectroscopic (ESR) studies.In the metal-catalyzed cycloisomerization reactions, an intramolecular cyclopropanation of allyl amides catalyzed by complexes of Rh(I) is described. These reactions proceeded via metal carbene intermediates, which were selectively generated by applying phosphine additives with different steric and electronic properties. Based on the mechanistic proposal, the synthesis of pyrroles from bicyclo[1.1.0]butanes was achieved using a Rh(I)/bidentate ligand catalytic system and hindered amides. Finally, cycloisomerization reactions of propargyl amides and ethers as well as electron-deficient bicyclo[1.1.0]butanes catalyzed by Pt(II) are described. These reactions proceeded via a series of carbene intermediates to give polycyclic nitrogen- and oxygen-containing heterocycles, which could be of utility in research and development