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Dale L. Boger - One of the best experts on this subject based on the ideXlab platform.
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synthesis characterization and cycloaddition reactivity of a monocyclic aromatic 1 2 3 5 tetrazine
Journal of the American Chemical Society, 2019Co-Authors: Dale L. BogerAbstract:Herein we disclose the synthesis and full characterization of the first monocyclic aromatic 1,2,3,5-tetrazine, 4,6-diphenyl-1,2,3,5-tetrazine. Initial studies of its cycloaddition reactivity, mode, regioselectivity, and scope illustrate that it participates as the 4π-component of well-behaved inverse electron demand Diels-Alder reactions where it preferentially reacts with electron-rich or strained dienophiles. It was found to exhibit an intrinsic reactivity comparable to that of the isomeric 3,6-diphenyl-1,2,4,5-tetrazine, display a single mode of cycloaddition with reaction only across C4/N1 (no N2/N5 cycloaddition observed), proceed with a predictable regioselectivity (dienophile most electron-rich atom attaches to C4), and manifest additional reactivity complementary to the isomeric 1,2,4,5-tetrazines. It not only exhibits a remarkable cycloaddition reactivity, surprisingly good stability (e.g., stable to chromatography, long-term storage, presence of H2O even as reaction co-solvent), and broad cycloaddition scope, but it also displays powerful orthogonal reactivity with the 1,2,4,5-tetrazines. Whereas the latter reacts at extraordinary cycloaddition rates with strained dienophiles (tetrazine ligation), the new and isomeric 1,2,3,5-tetrazine displays similarly remarkable cycloaddition rates and efficiencies with Amidines (1,2,3,5-tetrazine/Amidine ligation). The crossover reactivities (1,2,4,5-tetrazines with Amidines and 1,2,3,5-tetrazines with strained dienophiles) are sufficiently low to indicate they may be capable of use concurrently without competitive reactions.
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Synthesis, Characterization, and Rapid Cycloadditions of 5‑Nitro-1,2,3-triazine
2018Co-Authors: Christopher M. Glinkerman, Dale L. BogerAbstract:The synthesis, characterization, and a study of the cycloaddition reactions of 5-nitro-1,2,3-triazine (3) are reported. The electron-deficient nature of 3 permits rapid cycloaddition with a variety of electron-rich dienophiles, including Amidines, enamines, enol ethers, ynamines, and ketene acetals in high to moderate yields. 1H NMR studies of a representative cycloaddition reaction between 3 and an Amidine revealed a remarkable reaction rate and efficiency (1 mM, 95%)
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Total Synthesis of [Ψ[C(S)NH]Tpg4]Vancomycin Aglycon, [Ψ[C(NH)NH]Tpg4]Vancomycin Aglycon, and Related Key Compounds: Reengineering Vancomycin for Dual d-Ala-d-Ala and d-Ala-d-Lac Binding
2012Co-Authors: Jian Xie, Akinori Okano, Joshua G. Pierce, Robert C. James, Simon Stamm, Christine M. Crane, Dale L. BogerAbstract:The total synthesis of [Ψ[C(S)NH]Tpg4]vancomycin aglycon (8) and its unique AgOAc-promoted single-step conversion to [Ψ[C(NH)NH]Tpg4]vancomycin aglycon (7), conducted on a fully deprotected substrate, are disclosed. The synthetic approach not only permits access to 7, but it also allows late-stage access to related residue 4 derivatives, alternative access to [Ψ[CH2NH]Tpg4]vancomycin aglycon (6) from a common late-stage intermediate, and provides authentic residue 4 thioamide and Amidine derivatives of the vancomycin aglycon that will facilitate ongoing efforts on their semisynthetic preparation. In addition to early stage residue 4 thioamide introduction, allowing differentiation of one of seven amide bonds central to the vancomycin core structure, the approach relied on two aromatic nucleophilic substitution reactions for formation of the 16-membered diaryl ethers in the CD/DE ring systems, an effective macrolactamization for closure of the 12-membered biaryl AB ring system, and the defined order of CD, AB, and DE ring closures. This order of ring closures follows their increasing ease of thermal atropisomer equilibration, permitting the recycling of any newly generated unnatural atropisomer under progressively milder thermal conditions where the atropoisomer stereochemistry already set is not impacted. Full details of the evaluation of 7 and 8 along with several related key synthetic compounds containing the core residue 4 Amidine and thioamide modifications are reported. The binding affinity of compounds containing the residue 4 Amidine with the model d-Ala-d-Ala ligand 2 was found to be only 2–3 times less than the vancomycin aglycon (5), and this binding affinity is maintained with the model d-Ala-d-Lac ligand 4, representing a nearly 600-fold increase in affinity relative to the vancomycin aglycon. Importantly, the Amidines display effective dual, balanced binding affinity for both ligands (Ka 2/4 = 0.9–1.05), and they exhibit potent antimicrobial activity against VanA resistant bacteria (E. faecalis, VanA VRE) at a level accurately reflecting these binding characteristics (MIC = 0.3–0.6 μg/mL), charting a rational approach forward in the development of antibiotics for the treatment of vancomycin-resistant bacterial infections. In sharp contrast, 8 and related residue 4 thioamides failed to bind either 2 or 4 to any appreciable extent, do not exhibit antimicrobial activity, and serve to further underscore the remarkable behavior of the residue 4 Amidines
Roy G Gordon - One of the best experts on this subject based on the ideXlab platform.
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synthesis of 5 5 bicyclic Amidines as ligands for thermally stable vapor deposition precursors
Organometallics, 2017Co-Authors: Eugene S Beh, Liuchuan Tong, Roy G GordonAbstract:We describe the syntheses of three fully aliphatic 5,5-bicyclic Amidines. The syntheses are facile and scalable and can be easily modified to produce other 5,5-bicyclic Amidine ligands with other substitution patterns. Treatment of one of the ligands with KHMDS and subsequent transmetalation with CuCl resulted in a dimeric copper(I) bicyclic amidinate complex in 55% yield after recrystallization. This modestly air stable complex exhibits good volatility and thermal decomposition rates 1 order of magnitude lower than those of a similar, but acyclic, copper(I) amidinate. Together, the ligands enable a general method for producing a library of thermally stable metal amidinate precursors with a wide variety of metals for use in vapor deposition.
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Synthesis of 5,5-Bicyclic Amidines as Ligands for Thermally Stable Vapor Deposition Precursors
2017Co-Authors: Eugene S Beh, Liuchuan Tong, Roy G GordonAbstract:We describe the syntheses of three fully aliphatic 5,5-bicyclic Amidines. The syntheses are facile and scalable and can be easily modified to produce other 5,5-bicyclic Amidine ligands with other substitution patterns. Treatment of one of the ligands with KHMDS and subsequent transmetalation with CuCl resulted in a dimeric copper(I) bicyclic amidinate complex in 55% yield after recrystallization. This modestly air stable complex exhibits good volatility and thermal decomposition rates 1 order of magnitude lower than those of a similar, but acyclic, copper(I) amidinate. Together, the ligands enable a general method for producing a library of thermally stable metal amidinate precursors with a wide variety of metals for use in vapor deposition
Ewa D Raczynska - One of the best experts on this subject based on the ideXlab platform.
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experimental and theoretical evidence of basic site preference in polyfunctional superbasic amidinazine n1 n1 dimethyl n2 β 2 pyridylethyl formAmidine
Journal of Organic Chemistry, 2004Co-Authors: Ewa D Raczynska, Malgorzata Darowska, Iwona Dabkowska, Michele Decouzon, Jeanfrancois Gal, Pierrecharles Maria, Christine Dubin PoliartAbstract:The gas-phase basicity (GB) of the flexible polyfunctional N1,N1-dimethyl-N2-β-(2-pyridylethyl)formAmidine (1) containing two potential basic sites (the ring N-aza and the chain N-imino) is obtained from proton-transfer equilibrium constant measurements, using Fourier-transform ion-cyclotron resonance mass spectrometry. Comparison of the experimental GB obtained for 1 with those reported for model Amidines and azines indicates that the chain N-imino in the Amidine group is the favored site of protonation. Semiempirical (AM1) and ab initio calculations (HF, MP2, and DFT), performed for 1 and its protonated forms, confirm this interpretation. These results are in contrast to those found previously for N1,N1-dimethyl-N2-azinylformAmidines (containing the Amidine function directly linked to the azinyl ring), in which the ring N-aza is the most basic site in the gas phase. The separation of the two potential basic sites in 1 by the ethylene chain interrupts the resonance conjugation between the two functions a...
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semiempirical am1 studies of possible and preferred site s of porotnation in the gas phase for polyfunctional nitrogen bases n1 n1 dimethyl n2 azinylformAmidines
Bulletin of the Chemical Society of Japan, 1997Co-Authors: Ewa D Raczynska, Robert W TaftAbstract:Proton affinities for seven polyfunctional nitrogen bases (N1,N1-dimethyl-N2-azinylformAmidines) containing one Amidine moiety and one, two or three nitrogen atoms in ortho-, meta-, and/or para-positions of the heterocyclic six-membered group have been predicted by semiempirical AM1 method. The preferred site(s) of protonation and exceptionally high gas-phase basicity of N1,N1-dimethyl-N2-azinylformAmidines containing 2-azinyl group antiperiplanar to the functional carbon atom in the Amidine moiety have been discussed. The effects of one group on the basicity of the other one have been compared with those found for the corresponding model Amidines and azines.
Yoshio Furusho - One of the best experts on this subject based on the ideXlab platform.
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photocontrolled template directed synthesis of complementary double helices assisted by amidinium carboxylate salt bridge formation
Chemical Science, 2013Co-Authors: Junki Tanabe, Daisuke Taura, Hidekazu Yamada, Yoshio FurushoAbstract:The template-directed imine-bond forming reactions between chiral Amidines or achiral carboxylic acids monomers bearing a formyl or an amino group at one end were remarkably accelerated 34- or 10-fold in chloroform in the presence of the corresponding optically inactive carboxylic acid dimer or optically active Amidine dimer linked by a trans-azobenzene unit as the template, respectively. The cis-azobenzene-linked carboxylic acid template markedly slowed the monomer conversions, and hence a reversible photocontrolled dimerization was achieved by light-induced cis–trans isomerization upon alternative irradiation with UV and visible light.
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chiral amplification in double stranded helical polymers through chiral and achiral amidinium carboxylate salt bridges
Polymer Journal, 2012Co-Authors: Wataru Makiguchi, Yoshio Furusho, Shinzo Kobayashi, Eiji YashimaAbstract:A series of m-terphenyl-based random copolymers of chiral and achiral Amidines, and their complementary homopolymers of achiral carboxylic acids were prepared by the copolymerization of a p-diiodobenzene derivative, with the diethynyl monomers containing a chiral or achiral Amidine group and a carboxyl group using the Sonogashira coupling reaction. The obtained chiral/achiral Amidine copolymers assembled into a double-stranded helical structure upon complexation with the complementary achiral homopolymer of carboxylic acids through interstrand amidinium−carboxylate salt bridges. The complexes exhibited characteristic induced cotton effects in the π-conjugated main-chain chromophore regions, indicating that the interstrand duplexes possess a preferred-handed double-helical structure. The effect of the chiral and achiral Amidine contents on the amplification of the helical chirality (‘the sergeants and soldiers effect’) during the interstrand double-helix formation was investigated by comparing the cotton effect patterns and intensities of the duplexes with those of the corresponding all-chiral Amidine-based double-helical polymer. m-Terphenyl-based random copolymers of chiral and achiral Amidines and its complementary homopolymer of achiral carboxylic acids self-assembled to form complementary double helices with a preferred-handed helical sense via interstrand amidinium–carboxylate salt bridges, thus showing induced cotton effects in the π-conjugated main-chain chromophore regions. A unique amplification of the helical chirality (‘the sergeants and soldiers effect’) was, for the first time, observed during the double-helix formation.
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thermodynamic and kinetic stabilities of complementary double helices utilizing amidinium carboxylate salt bridges
Journal of the American Chemical Society, 2012Co-Authors: Hidekazu Yamada, Yoshio FurushoAbstract:A series of dimer strands consisting of m-terphenyl backbones bearing complementary chiral or achiral Amidines and achiral carboxylic acid residues connected by various types of linkers, such as diacetylene, Pt(II)-acetylide, and p-diethynylbenzene linkages, were synthesized by a modular strategy, and their chiroptical properties on the complementary double helix formations were investigated by absorption, circular dichroism (CD), and 1H NMR spectroscopies. The thermodynamic and kinetic stabilities of the complementary double helices assisted by amidinium–carboxylate salt bridges are highly dependent on their linkages, and the thermodynamic analyses of the dimer duplexes revealed that the association constants increased in the order: Pt(II)-acetylide linker < p-diethynylbenzene linker < diacetylene linker, which is in agreement with the reverse order of their bulkiness. The substituents on the Amidine groups were also found to affect the stabilities on the duplexes and the association constants increased ...
Eugene S Beh - One of the best experts on this subject based on the ideXlab platform.
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synthesis of 5 5 bicyclic Amidines as ligands for thermally stable vapor deposition precursors
Organometallics, 2017Co-Authors: Eugene S Beh, Liuchuan Tong, Roy G GordonAbstract:We describe the syntheses of three fully aliphatic 5,5-bicyclic Amidines. The syntheses are facile and scalable and can be easily modified to produce other 5,5-bicyclic Amidine ligands with other substitution patterns. Treatment of one of the ligands with KHMDS and subsequent transmetalation with CuCl resulted in a dimeric copper(I) bicyclic amidinate complex in 55% yield after recrystallization. This modestly air stable complex exhibits good volatility and thermal decomposition rates 1 order of magnitude lower than those of a similar, but acyclic, copper(I) amidinate. Together, the ligands enable a general method for producing a library of thermally stable metal amidinate precursors with a wide variety of metals for use in vapor deposition.
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Synthesis of 5,5-Bicyclic Amidines as Ligands for Thermally Stable Vapor Deposition Precursors
2017Co-Authors: Eugene S Beh, Liuchuan Tong, Roy G GordonAbstract:We describe the syntheses of three fully aliphatic 5,5-bicyclic Amidines. The syntheses are facile and scalable and can be easily modified to produce other 5,5-bicyclic Amidine ligands with other substitution patterns. Treatment of one of the ligands with KHMDS and subsequent transmetalation with CuCl resulted in a dimeric copper(I) bicyclic amidinate complex in 55% yield after recrystallization. This modestly air stable complex exhibits good volatility and thermal decomposition rates 1 order of magnitude lower than those of a similar, but acyclic, copper(I) amidinate. Together, the ligands enable a general method for producing a library of thermally stable metal amidinate precursors with a wide variety of metals for use in vapor deposition