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Abstract Palladium‐catalyzed aryl amination and Heck arylation reactions are complementary transformations, generally requiring a suitable catalyst combination and a base. With substrates containing both an amino group and a vinyl moiety, control of C─N versus C─C reactivity can lead to regiodivergent functionalizations. With this focus, reactions of silyl‐protected 8‐vinyl 2'‐deoxyadenosine and adenosine with aryl bromides and iodides have been studied. Pd(OAc)₂, Pd₂(dba)₃, and preformed dichloro[1,1′‐bis(di‐t‐butylphosphino)ferrocene]palladium (II) (Pd‐118) were evaluated as metal sources. Ligands tested were Xantphos, DPEphos, BIPHEP, and DPPF, with Cs₂CO₃and K₃PO₄as bases. In toluene as solvent, the Pd(OAc)₂/Xantphos/Cs₂CO₃combination was uniquely capable of predominantN⁶arylation. Aryl bromides and iodides gave comparable product yields. Replacement of Cs₂CO₃with K₃PO₄redirected arylation from the nitrogen atom to the vinyl carbon atom, and all other catalyst, ligand, and base combinations gave C^vinylarylation as well. Simply switching from Pd(OAc)₂to Pd₂(dba)₃resulted in loss of theN⁶‐selectivity and C^vinylarylation was favored. Based upon these results, using two structurally similar catalytic systems sequential C^vinylandN⁶arylations of the nucleosides were accomplished. Some of the products were converted to other novel nucleoside analogues. Because some compounds were fluorescent, their photophysical properties were assessed experimentally and computationally. 

Abstract With interests in alkoxy radical formation on natural and artificial surfaces, a physical‐organic study was carried out with a Hammett series of triaryl phosphites (p‐MeO, H,p‐F, andp‐Cl) to trap adsorbed alkoxy radicals on silica nanoparticles. A mechanism which involves PhC (Me)₂O• and EtO• trapping in a cumylethyl peroxide sensitized homolysis reaction is consistent with the results. Thep‐F phosphite was able to indirectly monitor the alkoxy radical formation, and³¹P NMR readily enabled this exploration, but other phosphites of the series such as thep‐MeO phosphite were limited by hydrolysis reactions catalyzed by surface silanol groups. Fluorinated silica nanoparticles helped to suppress the hydrolysis reaction although adventitious water also plays a role in hindering efficient capture of the alkoxy radicals by the phosphite traps. 

Abstract The sensitized photooxidation ofortho‐prenyl phenol is described with evidence that solvent aproticity favors the formation of a dihydrobenzofuran [2‐(prop‐1‐en‐2‐yl)‐2,3‐dihydrobenzofuran], a moiety commonly found in natural products. Benzene solvent increased the total quenching rate constant (k_T) of singlet oxygen with prenyl phenol by ~10‐fold compared to methanol. A mechanism is proposed with preferential addition of singlet oxygen to prenyl site due to hydrogen bonding with the phenol OH group, which causes a divergence away from the singlet oxygen ‘ene’ reaction toward the dihydrobenzofuran as the major product. The reaction is a mixed photooxidized system since an epoxide arises by a type I sensitized photooxidation. 

Abstract Ru(II) complexes were synthesized with π‐expanding (phenyl, fluorenyl, phenanthrenyl, naphthalen‐1‐yl, naphthalene‐2‐yl, anthryl and pyrenyl groups) attached at a 1H‐imidazo[4,5‐f][1,10]phenanthroline ligand and 4,4′‐dimethyl‐2,2′‐bipyridine (4,4′‐dmb) coligands. These Ru(II) complexes were characterized by 1D and 2D NMR, and mass spectroscopy, and studied for visible light and dark toxicity to human malignant melanoma SK‐MEL‐28 cells. In the SK‐MEL‐28 cells, the Ru(II) complexes are highly phototoxic (EC₅₀ = 0.2–0.5 µm) and have low dark toxicity (EC₅₀ = 58–230 µm). The highest phototherapeutic index (PI) of the series was found with the Ru(II) complex bearing the 2‐(pyren‐1‐yl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline ligand. This high PI is in part attributed to the π‐rich character added by the pyrenyl group, and a possible low‐lying and longer‐lived³IL state due to equilibration with the³MLCT state. While this pyrenyl Ru(II) complex possessed a relatively high quantum yield for singlet oxygen formation (Φ_∆ = 0.84), contributions from type‐I processes (oxygen radicals and radical ions) are competitive with the type‐II (¹O₂) process based on effects of added sodium azide and solvent deuteration.