Photochemistry of N-aryl and N-alkyl dibenzothiophene sulfoximines.

N-phenyl dibenzothiophene sulfoximine has been demonstrated to produce phenyl nitrene and dibenzothiophene S-oxide upon irradiation with UV-A light, and dibenzothiophene S-oxide upon further irradiation releases triplet atomic oxygen. Thus, N-phenyl dibenzothiophene sulfoximine exhibits a rare dual-release capability in its photochemistry. In this work, N-substituted dibenzothiophene sulfoximine derivatives are irradiated with UV-A light to compare their photochemistry and quantum yield of dibenzothiophene S-oxide production with that of N-phenyl dibenzothiophene sulfoximine.

Insights into the Mechanism of O(P)-Mediated Oxidation of Alkenes through Kinetic Isotope Effects and Computational Modeling.

Photodeoxygenation of aryl sulfoxides, such as dibenzothiophene -oxide (DBTO), produces atomic oxygen [O(P)] in solution. The mechanism of alkene oxidation with O(P) remains uncertain. To address this, the current study utilized kinetic isotope effects (KIEs) and computational approaches to study the reaction of O(P) with styrene and its isotopologues.

Comparison of Low-Density Lipoprotein Oxidation by Hydrophilic O( P)-Precursors and Lipid-O( P)-Precursor Conjugates.

Lipid oxidation by reactive oxygen species (ROS) provide several different oxidation products that have been implicated in inflammatory responses. Ground state atomic oxygen [O( P)] is produced by the photodeoxygenation of certain heterocyclic oxides and has a reactivity that is unique from other ROS. Due to the reactive nature of O( P), the site of O( P)-generation is expected to influence the products in heterogenous solutions or environments.

Effects of photodeoxygenation on cell biology using dibenzothiophene S-oxide derivatives as O(P)-precursors.

Photodeoxygenation of dibenzothiophene S-oxide and its derivatives have been used to generate atomic oxygen [O(P)] to examine its effect on proteins, nucleic acids, and lipids. The unique reactivity and selectivity of O(P) have shown distinct oxidation products and outcomes in biomolecules and cell-based studies. To understand the scope of its global impact on the cell, we treated MDA-MB-231 cells with 2,8-diacetoxymethyldibenzothiophene S-oxide and UV-A light to produce O(P) without targeting a specific cell organelle.

Identifying cysteine residues susceptible to oxidation by photoactivatable atomic oxygen precursors using a proteome-wide analysis.

The reactivity profile of atomic oxygen [O(P)] in the condensed phase has shown a preference for the thiol group of cysteines. In this work, water-soluble O(P)-precursors were synthesized by adding aromatic burdens and water-soluble sulphonic acid groups to the core structure of dibenzothiophene--oxide (DBTO) to study O(P) reactivity in cell lysates and live cells. The photodeoxygenation of these compounds was investigated using common intermediates, which revealed that an increase in aromatic burdens to the DBTO core structure decreases the total oxidation yield due to competitive photodeoxygenation mechanisms.

Photochemistry of N-Phenyl Dibenzothiophene Sulfoximine.

Sulfoximines are popular scaffolds in drug discovery due to their hydrogen bonding properties and chemical stability. In recent years, the role of reactive intermediates such as nitrenes has been studied in the synthesis and degradation of sulfoximines. In this work, the photochemistry of N-phenyl dibenzothiophene sulfoximine [5-(phenylimino)-5H-5λ -dibenzo[b,d]thiophene S-oxide] was analyzed.

Photo-oxidation and Thermal Oxidations of Triptycene Thiols by Aryl Chalcogen Oxides.

Oxidation of thiols yield sulfenic acids, which are very unstable intermediates. As sulfenic acids are reactive, they form disulfides in the presence of thiols. However, sulfenic acids also oxidize to sulfinic acids (-SOH) and sulfonic acids (-SOH) at higher concentrations of oxidants.

Synthesis of triphenylphosphonium dibenzothiophene S-oxide derivatives and their effect on cell cycle as photodeoxygenation-based cytotoxic agents.

Photodeoxygenation of Dibenzothiophene-S-oxide (DBTO) in UV-A light produces atomic oxygen [O(P)] and the corresponding sulfide, dibenzothiophene (DBT). Recently, DBTO has been derivatized to study the effect of UV-A light-driven photodeoxygenation in lipids, proteins, and nucleic acids. In this study, two DBTO derivatives with triphenylphosphonium groups were synthesized to promote mitochondrial accumulation.

oxidations of low-density lipoprotein and RAW 264.7 cells with lipophilic O(P)-precursors.

A beneficial property of photogenerated reactive oxygen species (ROS) is the capability of oxidant generation within a specific location or organelle inside a cell. Dibenzothiophene -oxide (DBTO), which is known to undergo a photodeoxygenation reaction to generate ground state atomic oxygen [O(P)] upon irradiation, was functionalized to afford localization within the plasma membrane of cells. The photochemistry, as it relates to oxidant generation, was studied and demonstrated that the functionalized DBTO derivatives generated O(P).

Dibenzothiophene Sulfone Derivatives as Plasma Membrane Dyes.

Dibenzothiophene 5,5-dioxide (DBTOO) derivatives have recently been shown to processes utility as fluorescent cell dyes. In an effort to extend the functionality of DBTOO-based dyes to include the visualization of cellular membranes, two lipophilic DBTOO were synthesized and their ability to incorporate into the plasma membrane of HeLa cells was examined by fluorescent microscopy. The photophysical properties of the two new DBTOO derivatives were determined and both have good fluorescent quantum yields and a visible blue emission.

Evidence for diffusing atomic oxygen uncovered by separating reactants with a semi-permeable nanocapsule barrier.

Ground-state atomic oxygen [O(3P)] is an oxidant whose formation in solution was proposed but never proven. Polymer nanocapsules were used to physically separate dibenzothiophene S-oxide (DBTO), a source of O(3P), from an O(3P)-accepting molecule. Irradiation of polymer nanocapsules loaded with DBTO resulted in oxidation of the O(3P)-acceptor placed outside nanocapsules.

Asymmetric Dibenzothiophene Sulfones as Fluorescent Nuclear Stains.

Asymmetric dibenzothiophene S, S-dioxides (DBTOOs) were synthesized and their photophysical properties examined. Through examination, the molecules fluoresced at wavelengths between 371 and 492 nm with quantum yields of fluorescence nearing 0.59.

Thiol Reactivity toward Atomic Oxygen Generated during the Photodeoxygenation of Dibenzothiophene S-Oxide.

Aromatic heterocyclic oxides, such as dibenzothiophene S-oxide (DBTO), have been suggested to release ground state atomic oxygen [O(P)] upon irradiation, and as such, they have been used to create a condensed phase reactivity profile for O(P). However, thiols, which are highly reactive with O(P) in the gas phase, were not previously investigated. An earlier study of O(P) with proteins in solution indicated a preference for thiols.

Photodeoxygenation of dinaphthothiophene, benzophenanthrothiophene, and benzonaphthothiophene S-oxides.

Photoinduced deoxygenation of dibenzothiophene S-oxide (DBTO) has been suggested to release atomic oxygen [O((3)P)]. To expand the conditions and applications where O((3)P) could be used, generation of O((3)P) at longer wavelengths was desirable. The sulfoxides benzo[b]naphtho-[1,2,d]thiophene S-oxide, benzo[b]naphtho[2,1,d]thiophene S-oxide, benzo[b]phenanthro[9,10-d]thiophene S-oxide, dinaphtho[2,1-b:1',2'-d]thiophene S-oxide, and dinaphtho[1,2-b:2',1'-d]thiophene S-oxide all absorb light at longer wavelengths than DBTO.

Oxidation of Plasmalogen, Low-Density Lipoprotein and RAW 264.7 Cells by Photoactivatable Atomic Oxygen Precursors.

The oxidation of lipids by endogenous or environmental reactive oxygen species (ROS) generates a myriad of different lipid oxidation products that have important roles in disease pathology. The lipid oxidation products obtained in these reactions are dependent upon the identity of the reacting ROS. The photoinduced deoxygenation of various aromatic heterocyclic oxides has been suggested to generate ground state atomic oxygen (O[3P]) as an oxidant; however, very little is known about reactions between lipids and O(3P).

Redox switching of adenosine-5'-phosphosulfate kinase with photoactivatable atomic oxygen precursors.

Adenosine-5'-phosphosulfate kinase (APSK) catalyzes the phosphorylation of adenosine-5'-phospho-sulfate (APS) to 3'-phospho-APS (PAPS). In plants, this enzymatic activity is biochemically regulated through an intersubunit disulfide bond between Cys86 and Cys119 in the N-terminal loop of APSK. To examine if O((3)P) generated by the photodeoxygenation of 2,8-dihydroxymethyldibenzothiophene S-oxide could specifically oxidize APSK at its regulatory site, APSK was irradiated in the presence of 2,8-dihydroxymethyldibenzothiophene S-oxide.

Ultrafast spectroscopy and computational study of the photochemistry of diphenylphosphoryl azide: direct spectroscopic observation of a singlet phosphorylnitrene.

The photochemistry of diphenylphosphoryl azide was studied by femtosecond transient absorption spectroscopy, by chemical analysis of light-induced reaction products, and by RI-CC2/TZVP and TD-B3LYP/TZVP computational methods. Theoretical methods predicted two possible mechanisms for singlet diphenylphosphorylnitrene formation from the photoexcited phosphoryl azide. (i) Energy transfer from the (π,π*) singlet excited state, localized on a phenyl ring, to the azide moiety, thereby leading to the formation of the singlet excited azide, which subsequently loses molecular nitrogen to form the singlet diphenylphosphorylnitrene.

Computational investigation of the reaction mechanisms of nitroxyl and thiols.

Nitroxyl, or nitrosyl hydride, (HNO) is a pharmacologically relevant molecule whose physiological responses have been thought to result from modification of intracellular thiols. The reaction of HNO with thiols has been shown to lead to disulfides and sulfinamides. The free energies of reaction (DeltaG) and activation (DeltaG(++)) were determined for the reaction pathways of HNO and five different thiols using computational methods.

Computational study of the Curtius-like rearrangements of phosphoryl, phosphinyl, and phosphinoyl azides and their corresponding nitrenes.

The free energies of reaction (DeltaG) and activation (DeltaG) were determined for the Curtius-like rearrangement of dimethylphosphinoyl, dimethylphosphinyl, and dimethylphosphoryl azides as well as the corresponding singlet and triplet nitrenes by CBS-QB3 and B3LYP computational methods. From CASSCF calculations, it was established that the closed-shell configuration was the lower energy singlet state for each of these nitrenes. The triplet states of dimethylphosphinyl- and dimethylphosphorylnitrene are the preferred ground states.

Sulfur and selenium ylide bond enthalpies.

The bond dissociation enthalpies (BDEs) of sulfur and selenium ylides have been estimated by applying MP2/6-311++G(3df,2p)//MP2/6-31G(d,p), G3, and other computational methods. Computed sulfoxide bond enthalpies were compared to experimental results to ensure the reliability of the computational methods before extending to related compounds. The examined ylides include the following: sulfoxides, sulfilimines, S,C-sulfonium ylides, and selenoxides.

Aryl to aryl palladium migration in the Heck and Suzuki coupling of o-halobiaryls.

A novel 1,4-palladium migration between the o- and o'-positions of biaryls has been observed in organopalladium intermediates derived from o-halobiaryls. The organopalladium intermediates generated by this migration have been trapped either by a Heck reaction employing ethyl acrylate or by Suzuki cross-coupling using arylboronic acids. This palladium migration can be activated or deactivated by choosing the appropriate reaction conditions.

Ultrafast study of the photochemistry of 2-azidonitrobenzene.

[reaction: see text] Ultrafast time-resolved studies of the photochemistry of 2-azidonitrobenzene demonstrate that the lifetimes of excited singlet 2-azidonitrobenzene and 2-nitrophenylnitrene are 500 fs and 8.3 ps, respectively, in solution at ambient temperature. The singlet nitrene is a discrete intermediate but is too short lived to undergo bimolecular reactions.

Deoxygenation and other photochemical reactions of aromatic selenoxides.

Atomic oxygen O(3P) is a potent oxidant that has been well-studied in the gas phase. However, exploration of its reactivity in the condensed organic phase has been hampered by the lack of an appropriate source. Dibenzothiophene-S-oxide (DBTO) and related derivatives have been promoted as photochemical O(3P) sources but suffer from low quantum yields.