- Chemistry of bifunctional photoprobes. 1. Perfluoroaryl azido functionalized phosphorus hydrazides as novel photoreactive heterobifunctional chelating agents: High efficiency nitrene insertion on model solvents and proteins
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Synthesis and evaluation of a new class of photochemically activated heterobifunctional chelating agents for protein modification is described. Selective functionalization of perfluoroaryl azides by versatile phosphorus hydrazide ligating systems 2 and 3 for the complexation of transition metals and analogous radiometals form the basis for these new agents. The utility of the photogenerated precursors from these bifunctional agents to form covalent attachments is demonstrated through examination of C-H bond insertion on cyclohexane. Representative amide-coupled phosphorus hydrazides 5 and 6 provide > 78% insertion of the probe into unactivated C-H bonds of cyclohexane with short photolysis times. Photoconjugation of the photoactivable heterobifunctional chelating agent 6 and its Pd metalated analog 7 with HSA is also evaluated. The uncomplexed chelate appears to add to HSA with high efficiency, consistent with the observed 82% bond insertion into model solvents. Covalent attachment of 7, evaluated through the use of 109Pd, was estimated to be between 49% and 74% with the uncertainty arising because of prephotolysis association of the 109Pd complex with HSA. The application of in situ 19F NMR to distinguish between bond insertion and noninsertion processes is demonstrated. These results suggest that functionalized perfluoroaryl azido phosphorus hydrazides may find utility as heterobifunctional photolabeling agents for attaching radionuclides to proteins and antibodies.
- Pandurangi,Karra,Katti,Kuntz,Volkert
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- Rh2(II)-Catalyzed intermolecular N-Aryl aziridination of olefins using nonactivated N atom precursors
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The development of the first intermolecular Rh2(II)-catalyzed aziridination of olefins using anilines as nonactivated N atom precursors and an iodine(III) reagent as the stoichiometric oxidant is reported. This reaction requires the transfer of an N-aryl nitrene fragment from the iminoiodinane intermediate to a Rh2(II) carboxylate catalyst; in the absence of a catalyst only diaryldiazene formation was observed. This N-aryl aziridination is general and can be successfully realized by using as little as 1 equiv of the olefin. Di-, tri-, and tetrasubstituted cyclic or acylic olefins can be employed as substrates, and a range of aniline and heteroarylamine N atom precursors are tolerated. The Rh2(II)-catalyzed N atom transfer to the olefin is stereospecific as well as chemo- and diastereoselective to produce the N-aryl aziridine as the only amination product. Because the chemistry of nonactivated N-aryl aziridines is underexplored, the reactivity of N-aryl aziridines was explored toward a range of nucleophiles to stereoselectively access privileged 1,2-stereodiads unavailable from epoxides, and removal of the N-2,4-dinitrophenyl group was demonstrated to show that functionalized primary amines can be constructed.
- Deng, Tianning,Mazumdar, Wrickban,Yoshinaga, Yuki,Patel, Pooja B.,Malo, Dana,Malo, Tala,Wink, Donald J.,Driver, Tom G.
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supporting information
p. 19149 - 19159
(2021/11/23)
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- Acid-responsive organogel mediated by arene-perfluoroarene and hydrogen bonding interactions
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A phenyl and a 2,3,5,6-tetrafluorophenyl ring, each bearing a tris(n-dodecyloxy)benzylamine moiety via an amide bond, were tethered together through an imine linkage to give a non-covalent synthon (imine 1) with a strong capacity of supramolecular self-as
- Wu, Huixian,Ni, Ben-Bo,Wang, Chong,Zhai, Feng,Ma, Yuguo
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experimental part
p. 5486 - 5492
(2012/08/14)
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- SURFACE-MODIFIED POLYMER FILMS
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Surface-modified polymer films for coating are provided, wherein the surface is modified by covalent binding of nano- or micro-particles comprising a photoreactive species. The surface of the polymer film, e.g. a parylene film, may be modified by covalent
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Page/Page column
(2013/03/26)
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- Smartly designed photoreactive silica nanoparticles and their reactivity
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Monodisperse, colloidal silica nanoparticles (NPs) are being widely investigated due to a variety of applications in various fields of chemistry. Many works utilize incorporation of various functional groups to silica NPs for their further modifications. However, at present no benzophenone (BPh) or phenyl azide (PA) containing silica NPs exist. Upon UV irradiation BPh and PA form highly reactive species that react with any organic material. Here we present a convenient method for the preparation of novel hybrid photoreactive silica NPs (denoted as SiO2@photoreactive group) prepared by co-condensation of photoreactive organosilanes and tetraethyl orthosilicate (TEOS) to obtain SiO2@PA and SiO2@BPh NPs. The reactivity of these two types of silica NPs is compared to that of perfluorinated phenyl azide (PFPA) based SiO2 NPs. The reactivity evaluation is carried out by the reaction of the three types of SiO2 NPs with highly inert poly(2-chloro-paraxylelene) films. It is found that, in contrast to what is stated in the literature, PA is much more reactive than PFPA, when dealing with solid state photochemical reactions. Next, photoreactive silica NPs on polymer films are used as an intermediate functional phase for a second modification step using silane-based chemistry. A successful incorporation of amine functionality onto silica NPs is achieved by their reaction with 3-aminopropyltriethoxysilane (APTES) and is verified by fluorescence microscopy. This strategy provides a general and versatile route to efficient functionalization of silica by light.
- Peled, Anna,Naddaka, Maria,Lellouche, Jean-Paul
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supporting information; experimental part
p. 11511 - 11517
(2011/10/18)
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- Facile and Efficient Synthesis of 4-Azidotetrafluoroaniline: A New Photoaffinity Reagent
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p-Azidotetrafluoroaniline (1) was synthesized in 65-73% yield by two different methods employing a stable carbamate intermediate. The first method trapped the intermediate isocyanate generated via a modified Curtius rearrangement with 2-methyl-2-propanol or 2-(trimethylsilyl)ethanol to form the stable carbamates 2d and 2e, respectively. Benzoic acid 2c was first converted to its acid chloride with PCl5. Displacement of the chloride by NaN3 in acetone/water formed the acyl azide. Thermal rearrangement followed by the addition of the appropriate alcohols provided the carbamates. The acid labile carbamate 2d was deprotected with HCl/AcOH to provide 1, while trifluoroacetic acid was required to deprotect 2e and afford 1. In the second path, 1 was synthesized in five steps from pentafluoronitrobenzene (3a) in 65% overall yield. Compound 3a was converted into 4-azidotetrafluoronitrobenzene (3b) with NaN3 in 93% yield and was used without further purification to form 1,4-diaminotetrafluorobenzene (3c) by Sn/HCl reduction in 85% yield. The mono-9-fiuorenylmethoxycarbonyl (FMOC) derivative 3d was formed from 3c with FMOC-Cl and pyridine in EtOAc in 92% yield. Diazotization of 3d under anhydrous conditions with TFA/NaNO2 and NaN3 gave 3e in 87% yield. The aryl azide was formed with concurrent nitration of the 2-position of the fluorenyl system. The protecting group was removed with piperidine to afford 1 in 93% yield. Irradiation of 1 with 254 nm light in cyclohexane gave cyclohexylamine 11, diamine 3c, and azobenzene 12 as the primary products. The formation of C-H insertion product 11 indicates that 1 forms a singlet nitrene upon photolysis. Two heterobifunctional photoaffinity reagents iodoacetamide 9 and dansyl derivative 10 were prepared.
- Chehade, Kareem A. H.,Spielmann, H. Peter
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p. 4949 - 4953
(2007/10/03)
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- Synthesis of a Tetrafluoro-Substituted Aryl Azide and Its Protio Analogue as Photoaffinity Labeling Reagents for the Estrogen Receptor
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A tetrafluoro-substituted aryl azide 1 and its protio analogue 2, both photoaffinity labeling reagents for the estrogen receptor, have been prepared by direct coupling of the appropriately substituted 4-azidobenzoyl chloride with the electron rich C-3 of 6-methoxy-2-(4-methoxyphenyl)benzothiophene 3.This represents a rare example of aryl azide stability under Friedel-Crafts acylation conditions.Alternatively, the protio analogue 2 can also be prepared with the azide functionality masked as a phthaloyl-protected arylamine, and the tetrafluoro analogue 1, by direct displacement of a pentafluoroaryl derivative 20 with NaN3.Solution photolysis of tetrafluoro-substituted aryl azide (bis-methyl ether) 15 and its protio analogue 16 in toluene at 30 deg C results in relatively high yields of products derived from C-H insertion.Both azides 1 and 2 demonstrate favorable relative binding affinity (RBA) (1 = 10percent, 2 = 66percent, estradiol = 100percent) and photoinactivation efficiency (1 = 43percent, 2 = 55percent at 30 min) for the estrogen receptor (ER).The synthesis of both azides has been modified to accommodate a palladium-catalyzed tritium gas hydrogenolysis of an iodoaryl precursor at a late stage in the synthetic sequence, as will be needed to prepare them in radiolabeled form, and this procedure has been verified dy deuteration.This pair of compounds will allow a detailed evaluation of the role that fluorine substitution plays in the photochemistry and photocovalent attachment behavior of aryl azides in a complex biochemical system, the estrogen receptor.The radiosynthesis and further biochemical results will be presented elsewhere.
- Pinney, Kevin G.,Katzenellenbogen, John A.
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p. 3125 - 3133
(2007/10/02)
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- New Reagents for Photoaffinity Labeling: Synthesis and Photolysis of Functionalized Perfluorophenyl Azides
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Functionalized perfluorophenyl azides (PFPA) 2-6, 8-12, 14-19, and 21-29 were synthesized, allowing the attachment of PFPA to other molecules for application as photolabels.Two biactive molecules were modified by a PFPA as potential photoaffinity labeling reagents.Photolysis of two representative members was investigated.Photolysis of azide 4 in cyclohexane gave 57 percent of CH insertion product.When photolysis was carried out in the presence of diethylamine as a trapping reagent, it gave 65 percent of NH insertion product, and no ring expansion product was found.The nitro azide 19 showed a shoulder absorption in the longer wavelength compared to azide 4.Azide 19 gave less CH insertion and more aniline products compared to azide 4 when photolyzed in toluene, suggesting that the nitro group accelerates intersystem crossing of the singlet nitrene or the singlet excited azide.Collectively, our results demonstrate that the functionalized PFPA investigated are much better in undergoing CH insertion than their nonfluorinated analogues and suggest that they may constitute an improved series of photolabeling reagents.
- Keana, John F. W.,Cai, Sui Xiong
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p. 3640 - 3647
(2007/10/02)
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- FUNCTIONALIZED PERFLUOROPHENYL AZIDES. NEW REAGENTS FOR PHOTOAFFINITY LABELING
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Several substituted perfluorophenyl azides capable of attachement to other molecules by an acylation reaction were synthesized for use as photoaffinity labeling reagents.
- Keana, John W.,Cai,Sui Xiong
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p. 151 - 154
(2007/10/02)
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