The electrochemical reduction mechanisms of 2 synthesized flavins (Flox) were examined in detail in deoxygenated solutions of DMSO containing varying amounts of water, utilizing variable scan rate cyclic voltammetry (ν = 0.1-20 V s(-1)), controlled-potential bulk electrolysis, and UV-vis spectroscopy. Flavin 1, which contains a hydrogen atom at N(3), is capable of donating its proton to other reduced flavin species. After 1e(-) reduction, the initially formed Fl(•-) receives a proton from another Flox to form FlH(•) (and concomitantly produce the deprotonated flavin, Fl(-)), although the equilibrium constant for this process favors the back reaction. Any FlH(•) formed at the electrode surface immediately undergoes another 1e(-) reduction to form FlH(-), which reacts with Fl(-) to form 2 molecules of Fl(•-). Further 1e(-) reduction of Fl(•-) at more negative potentials produces the dianion, Fl(2-), which can also be protonated by another Flox to form FlH(-) and Fl(-). Flavin 2, which is methylated at N(3) (and therefore has no acidic proton), undergoes a simple chemically reversible 1e(-) reduction process in DMSO provided the water content is low (<100 mM). Further 1e(-) reduction of Fl(•-) (from flavin 2) at more negative potentials leads to the dianion, Fl(2-), which is protonated by trace water in solution to form FlH(-), similar to the mechanism of flavin 1 at high scan rates. Addition of sufficient amounts of water to nonaqueous solvents results in protonation of the anion radical species, Fl(•-), for both flavins, causing an increase in the amount of FlH(-) in solution. This behavior contrasts with what is observed for quinones, which are also reduced in two 1e(-) steps in aprotic organic solvents to form the radical anions and dianions, but are able to exist in hydrogen-bonded forms (with trace or added water) without undergoing protonation.

An efficient silver triflate-catalyzed tandem hydroamination/hydroarylation cascade generating 1'-allylspiro[indene-1,2'-indolin]-3'-ones from 1-(2-allylamino)phenyl-4-hydroxy-but-2-yn-1-ones is described. The reaction conditions are mild and general in scope and proceed to highly functionalized spiro-targets in high yield. This novel class of molecule possesses both the privileged indene and indolin-3-one scaffold, which may lead to possible pharmacological applications.

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.

Flavin derivatives with an extended π-conjugation were synthesized in moderate to good yields from aryl bromides via a Buchwald-Hartwig palladium catalyzed amination protocol, followed by condensation of the corresponding aromatic amines with violuric acid. The electronic properties of the new compounds were investigated by absorption and emission spectroscopy, cyclic voltammetry, density functional theory (DFT) and time dependent density functional theory (TDDFT). The compounds absorb up to 550 nm and show strong luminescence. The photoluminescence quantum yields ϕPL measured in dichloromethane reach 80% and in PMMA (poly(methyl methacrylate)) 77%, respectively, at ambient temperature. The electrochemical redox behaviour of π-extended flavins follows the mechanism previously described for the parent flavin.

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