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A catalytic system to synthesize α-amino amides from isocyanates and ketimines has been developed using visible light iridium photoredox catalysis via umpolung reactivity of ketimines. Cross-couplings between diverse ketimine and isocyanate substrates have been evaluated, affording the desired α-amino amide products in good yields. In addition, a metal-free catalytic system using perylene and N,N-diisopropylethylamine has been developed. Finally, single-step synthesis of the psychoactive drug benzodiazepine-2-one analogue from one of the coupling products has been achieved, indicating the great application potential of the synthetic method developed herein.

Herein, we report a highly efficient and practical method for pyridine-derived heterobiaryl synthesis through palladium-catalyzed electrophilic functionalization of easily available pyridine-derived quaternary phosphonium salts. The nice generality of this reaction was goes beyond arylation, enabling facile incorporation of diverse carbon-based fragments, including alkenyl, alkynyl, and also allyl fragments, onto the pyridine core. Notably, the silver salt additive is revealed to be of vital importance for the success of this transformation and its pivotal role as transmetallation mediator, which guarantees a smooth transfer of pyridyl group to palladium intermediate, is also described.

Organosilicon compounds have attracted synthetic organic chemists because they have a potential to be used as the organometallic reagents which are stable in the air and water. As the recent transition metal-catalyzed reactions developed, catalytic reactions with organosilicon compounds have been also studied. However, most of the reported transition metal-catalyzed reactions with organosilicon compounds require the addition of at least a stoichiometric amount of fluoride salt and/or the introduction of heteroatom such as halogen or alkoxy group on the silicon atom. These activation methods are not economical because fluoride sources are expensive. Introduction of a heteroatom on the silicon atom makes the reagents unstable against hydrolysis and self-condensation. Thus synthetic organic chemists have studied on the methods to activate C–Si bonds of tetraorganosilicon compounds without adding any additional reagents. In this thesis, the author describes a novel synthetic reaction of tetraorganosilicon compounds, triorgano(vinyl)- and triorgano(acyl)silanes, catalyzed by a rhodium complex. DOCTOR OF PHILOSOPHY (SPMS)

A visible-light-promoted oxo-sulfonylation of ynamides with sulfonic acids is reported, giving rise to a collection of functionalized α-sulfonylated amides in a straightforward manner. The reaction proceeds sequentially through a cascade of electrophilic addition and photoinduced sulfonyl radical-sustained skeleton rearrangement. The high atom economy, mild reaction conditions, and wide substrate scope comprised the merits of this synthetic transformation.

Systematic synthesis of a number of new phenolic compounds with structures similar to vitamin E led to the identification of several sterically hindered compounds that when electrochemically oxidised in acetonitrile in a -2e(-)/-H(+) process formed phenoxonium diamagnetic cations that were resistant to hydrolysis reactions. The reactivity of the phenoxonium ions was ascertained by performing cyclic voltammetric scans during the addition of carefully controlled quantities of water into acetonitrile solutions, with the data modelled using digital simulation techniques.

The electrochemical behavior of vitamins D 2 and D 3 were examined by performing cyclic voltammetry (CV), rotating disk electrode voltammetry, controlled potential electrolysis and chemical oxidation in aprotic organic solvents. Both vitamins were electrochemically oxidized in dichloromethane and acetonitrile ( E p ox ∼ +0.8 vs. (Fc/Fc + )/V, where E p ox is the anodic peak potential and Fc = ferrocene) via a one-electron chemically irreversible process on the short voltammetric time scale (≤ seconds). Varying the scan rate (0.1 V s −1 to 20 V s −1 ) and temperature (233 K to 293 K) did not strongly affect the voltammetric response recorded on platinum and glassy carbon electrode surfaces with the oxidation process remaining chemically irreversible over the range of scan rates and temperatures tested, indicating that the initially formed cation radical was not long-lived. Repetitive CV experiments indicated that the oxidized product partially adsorbed onto the electrode surface, resulting in diminishing peak currents with multiple scans. Bulk controlled potential electrolysis of the vitamin D compounds performed by alternating several cycles of oxidative electrolysis and reductive pulsed stripping proved to be effective in stripping the adsorbed species off the electrode surfaces. Longer time scale bulk electrolysis experiments led to the detection of a new oxidation peak appearing at less positive potentials as the electrolysis progressed, suggesting that the compounds underwent oxidation on long time scales (minutes to hours) via a two electron process. The vitamins were most likely initially oxidized via one-electron (E-step) to form a cation radical, which reacts homogeneously in two chemical steps (C-steps) where one chemical step is fast ( 1 s). On the electrolysis timescale, the oxidized product then undergoes a second electron transfer (E) at less positive potentials, so the overall mechanism is an ECCE process. Chemical oxidation of vitamin D 3 with 2 mol equiv of the one-electron oxidant, NO + SbF 6 − in acetonitrile/dichloromethane 1:4 ratio (v/v) resulted in the complete oxidation of the starting material in an overall two-electron process, with NMR analysis of the reaction mixture indicating that the triene moiety is absent from the products.

The electrochemical behavior of bisphenol A (BPA) was examined using cyclic voltammetry, bulk electrolysis and chemical oxidation in aprotic organic solvents. It was found that BPA undergoes a chemically irreversible voltammetric oxidation process to form compounds that cannot be electrochemically converted back to the starting materials on the voltammetric timescale. To overcome the effects of electrode fouling during controlled potential electrolysis experiments, NO + was used as a one-electron chemical oxidant. A new product, hydroxylated bisdienone was isolated from the chemical oxidation of BPA with 4 mol equiv of NO + SbF 6 − in low water content CH 3 CN. The structure of the cation intermediate species was deduced and it was proposed that BPA is oxidized in a four-electron/two-proton process to form a relatively unstable dication which reacts quickly in the presence of water in acetonitrile (in a mechanism that is similar to phenols in general). However, as the water content of the solvent increased it was found that the chemical oxidation mechanism produced a nitration product in high yield. The findings from this study provide useful insights into the reactions that can occur during oxidative metabolism of BPA and highlight the possibility of the role of a bisdienone cation as a reactive metabolite in biological systems.

Retinal (R) can be sequentially voltammetrically reduced in CH3CN in two one-electron processes to form first the anion radical (R(•-)) at -1.75 (±0.04) V vs Fc/Fc(+) (Fc = ferrocene) then the dianion (R(2-)) at -2.15 (±0.04) V vs Fc/Fc(+). The anion radical undergoes a reversible dimerization reaction to form the dianion (R2(2-)) with a forward dimerization rate constant k(dim) = 8 × 10(2) L mol(-1) s(-1) and a reverse monomerization rate constant k(mon) = 2 × 10(-2) s(-1) at 295 K. All three anion species (anion radical, dianion, and dimer dianion) undergo hydrogen-bonding interactions with water that is present at millimolar levels in the solvent. As the water content of the solvent increases, the fate of the reduced compounds is determined by chemically irreversible hydrolysis reactions with H2O and decomposition reactions of the highly charged R(2-). Bulk-controlled potential electrolysis experiments combined with NMR analysis of the reaction solutions indicate that the reduction occurs at the aldehyde group of retinal. The electrochemical data obtained under a range of experimental conditions (varying voltammetric scan rates, temperatures, H2O content of solutions, and retinal concentrations) were modeled by digital simulation techniques to determine the kinetic and thermodynamic parameters associated with all of the homogeneous reactions.

1,3-Diene-2,3-diyl diesters are synthesized by rhodium-catalyzed homocoupling of (1-acyloxyvinyl)silanes. Double transmetalation between vinylsilane and rhodium intermediate in a single catalytic cycle is the key in this reaction. From the homocoupling products, symmetrical α-diketone and its monoacetal are easily synthesized.