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Effective healing of skin wounds is essential for our survival. Although skin has strong regenerative potential, dysfunctional and disfiguring scars can result from aberrant wound repair. Skin scarring involves excessive deposition and misalignment of ECM (extracellular matrix), increased cellularity, and chronic inflammation. Transforming growth factor-ß (TGFß) signaling exerts pleiotropic effects on wound healing by regulating cell proliferation, migration, ECM production, and the immune response. Although blocking TGFß signaling can reduce tissue fibrosis and scarring, systemic inhibition of TGFß can lead to significant side effects and inhibit wound re-epithelization. In this study, we develop a wound dressing material based on an integrated photo-crosslinking strategy and a microcapsule platform with pulsatile release of TGF-ß inhibitor to achieve spatiotemporal specificity for skin wounds. The material enhances skin wound closure while effectively suppressing scar formation in murine skin wounds and large animal preclinical models. Our study presents a strategy for scarless wound repair.

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A unified strategy involving visible-light-induced iminyl-radical formation has been established for the construction of pyridines, quinolines, and phenanthridines from acyl oximes. With fac-[Ir(ppy)3 ] as a photoredox catalyst, the acyl oximes were converted by 1 e(-) reduction into iminyl radical intermediates, which then underwent intramolecular homolytic aromatic substitution (HAS) to give the N-containing arenes. These reactions proceeded with a broad range of substrates at room temperature in high yield. This strategy of visible-light-induced iminyl-radical formation was successfully applied to a five-step concise synthesis of benzo[c]phenanthridine alkaloids.

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We report the direct observation of a bent geometry for a nonstabilized nitrile imine in a metal-coordination crystal. The photoinduced tetrazole ring rupture to release N(2) appears to depend on the size of voids around the N(3)-N(4) bond in the crystal lattice. We further observed the selective formation of the 1,3-addition product when a reactive nitrile imine was photogenerated in water. Overall, the bent nitrile imine geometry agrees with the 1,3-dipolar structure, a transient reactive species that mediates the photoinduced 1,3-dipolar cycloaddition in the aqueous medium.

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The reaction mechanism between Fischer carbene complexes and imines to produce beta-lactams has been studied by a combination of computational (DFT) and experimental methodologies. After the photogeneration of metalla-cyclopropanone species, the reaction initiates by 1,3-migration of the metal fragment from the former carbene carbon atom to the oxygen in the S o hypersurface. In spite of the endothermic nature of this rearrangement, it is biased by the more favorable HOMO(imine)-LUMO+1 interaction in the oxygen-coordinated ketene. This species reacts with the imine to yield metalla-zwitterions, which form the final products through a four electron conrotatory ring closure. The presence of the metal moiety during the whole reaction coordinate is demonstrated by the use of a chiral chromium(0) alkoxycarbene complex, which produces low but significant ee in the reaction with imines. The cis-trans stereoselection derives from the nucleophilic addition of the nitrogen atom of the imine to the oxygen-coordinated ketene, since there are no significant differences between the classical and the metallated processes in the electrocyclation step leading to the final 2-azetidinones.

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To evaluate the ability of dibenzothiophene N-substituted sulfilimines as photochemical nitrene sources, their photolyses in the presence of several trapping reagents, such as sulfides, olefins, and phosphorus compounds, were performed. In the reactions, the corresponding imino-transfer compounds, namely sulfilimines, aziridines, and iminophosphoranes, were formed in good yields, indicating dibenzothiophene N-tosyl and N-acylsulfilimines have a potent nature as nitrogen sources.

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Septet 3,5-difluoropyridyl-2,4,6-trinitrene along with quintet 2-azido-3,5-difluoropyridyl-4,6-dinitrene, quintet 4-azido-3,5-difluoropyridyl-2,6-dinitrene, triplet 2,6-diazido-3,5-difluoropyridyl-4-nitrene, and triplet 2,4-diazido-3,5-difluoropyridyl-6-nitrene have been obtained by photolysis of 2,4,6-triazido-3,5-difluoropyridine in solid argon at 4 K. The electronic and magnetic properties of the matrix-isolated nitrenes were studied using electron paramagnetic resonance (EPR) spectroscopy in combination with density functional theory (DFT) calculations. The fine-structure parameters of the nitrenes were determined with high accuracy from computer spectral simulations. All signals in the EPR spectra of the nitrenes randomly oriented in the solid phase were unambiguously assigned on the basis of eigenfield calculations of the Zeeman energy levels and angular dependencies of resonance fields from the direction of the applied magnetic field.

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The semiconductor catalyzed photoaddition of cyclopentene or cyclohexene to various novel electron-poor imines of type p-XC(6)H(4)(CN)C[double bond, length as m-dash]N(COPh) (X = H, F, Cl, Br, Me, MeO) was investigated as a function of the nature of the cadmium sulfide photocatalyst. Irradiation (lambda>/= 350 nm) of silica supported cadmium sulfide surprisingly did not afford the expected olefin-imine adducts but an imine hydrocyanation product via an unprecedented dark reaction. However, when silica was replaced by zinc sulfide as the support for cadmium sulfide, the expected homoallylic N-benzoyl-alpha-amino cyanides were isolated in yields of 65-84%. Thus, chemoselectivity is introduced through replacing an insulating by a semiconducting support, a hitherto unknown effect in semiconductor photocatalysis. From the sign of the time resolved photovoltage it is found that the mixed metal sulfide interface CdS/ZnS increases the lifetime of photogenerated electron-hole pairs by about one order of magnitude as compared to the SiO(2)/CdS system. The reaction rate increases with increasing imine sigma-Hammett constants and decreasing stability of intermediate benzyl radicals.

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Compounds containing the C==N group, such as imines and their derivatives, may undergo syn-anti isomerization by two different routes: 1) photochemically, by out-of-plane rotation around the carbon-nitrogen double bond through a "perpendicular" form, and 2) thermally, by in-plane nitrogen inversion through a "linear" transition state. When the two interconversions occur in sequence, a full, closed process is accomplished, restoring the initial state of the system along two different steps. In a chiral imine-type compound, for example, with an asymmetric center next to the C==N function, photoinduced rotation may be expected to occur in one sense in preference to the opposite one. Thus, photoisomerization followed by thermal isomerization in a chiral imine compound generates unidirectional molecular motion. Generally, imine-type compounds represent unidirectional molecular photomotors converting light energy into mechanical motion. As they are also able to undergo exchange of the carbonyl and amine partners, they present constitutional dynamics. Thus, imine-type compounds are double dynamic, motional, and constitutional devices.

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Rapid synthesis of quinoline-4-carboxylic acid derivatives has been achieved by reaction of 2-methoxy acrylates or acrylamides with N-arylbenzaldimines in acetonitrile under InCl3 catalysis and microwave irradiation. Isolated yields up to 57% within 3 min have been obtained. The Lewis acid and the microwave activation appeared as crucial parameters for the reaction. The role of indium chloride and ytterbium triflate was specified using 13C NMR data and model theoretical studies.

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A convenient method for the synthesis of 1,5-disubstituted imidazoles has been developed on a polymeric support using base-promoted 1,3-dipolar cycloaddition reaction of p-toluenesulfonylmethyl isocyanide (TOSMIC) with immobilized imines under microwave irradiation. The immobilized imines were synthesized by the reaction of various primary benzyl amines with 4-formyl-3-methoxyphenoxymethyl polystyrene in the presence of trimethyl orthoformate at room temperature. Cleavage from the polymeric support using trifluoroacetic acid gave the desired 1,5-disubstituted imidazoles with excellent yield and high purity.

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The photoisomerization kinetics of trifloxystrobin (TFS) in acetone under artificial sunlight is reported. HPLC analysis showed the TFS, a strobilurine fungicide of EE conformation, was converted into an equilibrium mixture of four isomers after illumination for 7 h. The isomers were identified as EZ, EE, ZZ, and ZE and were separated in the crystalline form by preparative HPLC and characterized by use of a variety of spectroscopic techniques. The quantum yield and reaction constants for the isomerization reactions were determined. The detailed spectral features of the individual isomers measured by UV, IR, Raman, NMR and mass spectroscopy are presented and compared. The spectra of the isomers were found to be very characteristic, with good analytical significance.

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Reactions of ketenes generated from alpha-diazoketones with a series of acyclic and cyclic imines were investigated under both microwave and photoirradiation conditions. The results indicate that the zwitterionic azabutadiene-type intermediates yielded from imines and ketenes undergo a conrotatory ring closure exclusively to produce beta-lactams. It is notable that no Woodward-Hoffmann product was found under the ultraviolet irradiation. The photoirradiation-induced Staudinger reaction shows a different stereoselectivity from the electrocyclic reaction of substituted 1,3-butadiene.

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Two new complexes fac-[Re(NCS)(CO)3(N,N)] (N,N = 2,2'-bipyridine (bpy), di-iPr-N,N-1,4-diazabutadiene (iPr-DAB)) were synthesized and their molecular structures determined by X-ray diffraction. UV-vis absorption, resonance Raman, emission, and picosecond time-resolved IR spectra were measured experimentally and calculated with TD-DFT. A good agreement between experimental and calculated ground- and excited-state spectra is obtained, but only if the solvent (MeCN) is included into calculations and excited state structures are fully optimized at the TD-DFT level. The lowest excited states of the bpy and iPr-DAB complexes are assigned by TD-DFT as 3aA' by comparison of calculated and experimental IR spectra. Excited-state lifetimes of 23 ns and ca. 625 ps were determined for the bpy and DAB complex, respectively, in a fluid solution at room temperature. Biexponential emission decay (1.3, 2.7 micros) observed for [Re(NCS)(CO)3(bpy)] in a 77 K glass indicates the presence of two unequilibrated emissive states. Low-lying electronic transitions and excited states of both complexes have a mixed NCS --> N,N ligand-to-ligand and Re --> N,N metal-to-ligand charge-transfer character (LLCT/MLCT). It originates in mixing between Re d(pi) and NCS pi characters in high-lying occupied MOs. Experimentally, the LLCT/MLCT mixing in the lowest excited state is manifested by shifting the nu(CO) and nu(NC) IR bands to higher and lower wavenumbers, respectively, upon excitation. Resonant enhancement of both nu(CO) and nu(NC) Raman bands indicates that the same LLCT/MLCT character mixing occurs in the lowest allowed electronic transition.

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