New methods for transition metal-mediated and transition metal-catalyzed organic synthesis

This dissertation is divided into three parts. The first part describes the preparation of organometallic substrates and their evaluation in free radical reactions. Two methods of radical generation were investigated in these studies. The first method is the tributyltin hydride-mediated radical reduction of a series of homologous ferrocenylalkyl halides and thiocarbamates. It was found, in general, that a shorter tether between the ferrocene ring and the radical precursor tend to give a larger proportion of simple reduction products, while the longer-tethered compounds engaged in dimerization reactions more readily than reduction. The halides tended to favor reduction products, while thiocarbamates gave a higher incidence of dimerization. Radical cyclizations were also attempted, using terminally functionalized ferrocenoylalkenes under samarium iodide conditions. These alkenes were prepared by olefin cross-metathesis with the second-generation Grubbs' catalyst. This improved catalyst allowed for high-yielding preparation of compounds with electron-withdrawing substituents at the alkene terminus. The cyclization reactions proceed well when the alkene substituent is strongly electron withdrawing. Terminal alkenes or those with weaker electron withdrawing groups undergo simple reduction instead of cyclization.; The second part describes the application of a palladium-catalyzed aryl amidation reaction for the preparation of chiral, non-racemic aryl lactams. Using the conditions of Buchwald and Hartwig, electron-deficient aryl bromides were successfully coupled with a protected pyrroglutamate derivative in up to 95% yield. This new methodology for preparation of N-aryl lactams has subsequently been used in our group in the total synthesis of the Martinella alkaloids.; The third part encompasses the use of fluorinated tris(pyrazolyl)borato copper(I) and silver(I) complexes as catalysts for nitrene and carbene transfer. The copper complexes represent a new class of highly fluorinated, air-stable aziridination catalysts. These complexes were successfully used at 5 mol% loading to catalyze the aziridination of alkenes with a nitrene source in low to excellent yield (18--99%). The silver-based systems have been employed in carbene transfer processes, and it was found that these complexes possess the ability to catalyze reactions that are not possible or are difficult with other known catalysts. The carbene transfer reactions that were surveyed include cyclopropanation, the Buchner reaction, carbene insertion into carbon-halogen bonds, and insertion into unactivated carbon-hydrogen bonds.