- Mild C?F Activation in Perfluorinated Arenes through Photosensitized Insertion of Isonitriles at 350 nm
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Fluorinated compounds have become important in the fields of agrochemical industry, pharmaceutical chemistry and materials sciences. Accordingly, various methods for their preparation have been developed in the past. Fluorinated compounds can be accessed via conjugation with fluorinated building blocks, via C?H fluorination or via selective activation of perfluorinated compounds to give the partially fluorinated congeners. Especially the direct activation of C?F bonds, one of the strongest σ-bonds, still remains challenging and new strategies for C?F activation are desirable. Herein a method for the photochemical activation of aromatic C?F bonds is presented. It is shown that isonitriles selectively insert into aromatic C?F bonds while aliphatic C?F bonds remain unaffected. Mechanistic studies reveal the reaction to proceed via the indirect excitation of the isonitrile to its triplet state by photoexcited acetophenone at 350 nm. Due to the relatively mild light used, the process shows high functional group tolerance and various compounds of the class of benzimidoyl fluorides are accessible from aryl isonitriles and commercially available perfluorinated arenes. (Figure presented.).
- Weidlich, Frauke,Esumi, Naoto,Chen, Dongyang,Mück-Lichtenfeld, Christian,Zysman-Colman, Eli,Studer, Armido
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p. 376 - 383
(2019/11/19)
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- Heterocyclopentanediyls vs heterocyclopentadienes: A question of silyl group migration
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The reaction of the singlet biradical [P(μ-NHyp)]2 (Hyp = hypersilyl, (Me3Si)3Si) with different isonitriles afforded a series of five-membered N2P2C heterocycles. Depending on the steric bulk of the substituent at the isonitrile, migration of a Hyp group was observed, resulting in two structurally similar but electronically very different isomers. As evidenced by comprehensive spectroscopic and theoretical studies, the heterocyclopentadiene isomer may be regarded as a rather unreactive closed-shell singlet species with one localized N=P and one C=P double bond, whereas the heterocyclopentanediyl isomer represents an open-shell singlet biradical with interesting photochemical properties, such as photoisomerization under irradiation with red light to a [2.1.0]- housane-type species.
- Beer, Henrik,Bresien, Jonas,Michalik, Dirk,R?lke, Anne-Kristin,Schulz, Axel,Villinger, Alexander,Wustrack, Ronald
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supporting information
p. 14435 - 14445
(2020/12/29)
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- Isocyanide 2.0
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The isocyanide functionality due to its dichotomy between carbenoid and triple bond characters, with a nucleophilic and electrophilic terminal carbon, exhibits unusual reactivity in organic chemistry exemplified for example in the Ugi reaction. Unfortunately, the over proportional use of only a few isocyanides hampers novel discoveries about the fascinating reactivity of this functional group. The synthesis of a broad range of isocyanides with multiple functional groups is lengthy, inefficient, and exposes the chemist to hazardous fumes. Here we present an innovative isocyanide synthesis overcoming these problems by avoiding the aqueous workup which we exemplify by parallel synthesis from a 0.2 mmol scale performed in 96-well microtiter plates up to a 0.5 mol multigram scale. The advantages of our methodology include an increased synthesis speed, very mild conditions giving access to hitherto unknown or highly reactive classes of isocyanides, rapid access to large numbers of functionalized isocyanides, increased yields, high purity, proven scalability over 5 orders of magnitude, increased safety and less reaction waste resulting in a highly reduced environmental footprint. For example, the hitherto believed to be unstable 2-isocyanopyrimidine, 2-acylphenylisocyanides and even o-isocyanobenzaldehyde could be accessed on a preparative scale and their chemistry was explored. Our new isocyanide synthesis will enable easy access to uncharted isocyanide space and will result in many discoveries about the unusual reactivity of this functional group. This journal is
- Ahmadian-Moghaddam, Maryam,D?mling, Alexander,Patil, Pravin
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supporting information
p. 6902 - 6911
(2020/11/09)
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- Reversible switching between housane and cyclopentanediyl isomers: An isonitrile-catalysed thermal reverse reaction
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The photo-isomerization of an isolable five-membered singlet biradical based on C, N, and P ([TerNP]2CNDmp, 2a) selectively afforded a closed-shell housane-type isomer (3a) by forming a transannular P-P bond. In the dark, the housane-type species re-isomerized to the biradical, resulting in a fully reversible overall process. In the present study, the influence of tBuNC on the thermal reverse reaction was investigated: The isonitrile acted as a catalyst, thus allowing control over the thermal reaction rate. Moreover, tBuNC also reacted with the biradical to form an adductspecies ([TerNP]2CNDmp·CNtBu, 4a), which can be regarded as the resting state of the system. The reactive species 2a and 3a could be re-generated in situ by irradiation with red light. The results of this study extend our understanding of this new class of molecular switches.
- Beer, Henrik,Bresien, Jonas,Michalik, Dirk,Schulz, Axel,Villinger, Alexander
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supporting information
p. 13986 - 13992
(2020/11/02)
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- Magnesium Aldimines Prepared by Addition of Organomagnesium Halides to 2,4,6-Trichlorophenyl Isocyanide: Synthesis of 1,2-Dicarbonyl Derivatives
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The selective addition of organomagnesium reagents to 2,4,6-trichlorophenyl isocyanide leading to magnesiated aldimines is reported. These aldimines react with Weinreb amides, ketones, or carbonates to provide the corresponding carbonyl derivatives after acidic cleavage. This allows for an efficient synthesis of 1,2-dicarbonyl compounds and α-hydroxy ketones.
- Schw?rzer, Kuno,Bellan, Andreas,Z?schg, Maximilian,Karaghiosoff, Konstantin,Knochel, Paul
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p. 9415 - 9418
(2019/05/10)
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- Crystal structures and spectroscopic characterization of MBr2(CNXyl)n (M = Fe and Co, n = 4; M = Ni, n = 2; Xyl = 2,6-dimethylphenyl), and of formally zero-valent iron as a cocrystal of Fe(CNXyl)5 and Fe2(CNXyl)9
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Structures and spectroscopic characterization of the divalent complexes cisdibromidotetrakis( 2,6-dimethylphenyl isocyanide)iron(II) dichloromethane 0.771-solvate, [FeBr2(C9H9N)4]-0.771CH2Cl2 or cis-FeBr2(CNXyl)4-0.771CH2Cl2 (Xyl = 2,6-dimethylphenyl), trans-dibromidotetrakis(2,6-dimethylphenyl isocyanide)-iron(II), [FeBr2(C9H9N)4] or trans-FeBr2(CNXyl)4, trans-dibromidotetrakis(2,6-dimethylphenyl isocyanide)cobalt(II), [CoBr2(C9H9N)4] or trans-CoBr2(CNXyl)4, and trans-dibromidobis(2,6-dimethylphenyl isocyanide)nickel(II), [NiBr2(C9H9N)2] or trans-NiBr2(CNXyl)2, are presented. Additionally, crystals grown from a cold diethyl ether solution of zero-valent Fe(CNXyl)5 produced a structure containing a cocrystallization of mononuclear Fe(CNXyl)5 and the previously unknown dinuclear [Fe(CNXyl)3]2(-2-CNXyl)3, namely pentakis(2,6-dimethylphenyl isocyanide)iron(0) tris(-2-2,6-dimethylphenyl isocyanide)bis[tris(2,6-dimethylphenyl isocyanide)iron(0)], [Fe(C9H9N)5][Fe2(C9H9N)9]. The (M)C- N-C(Xyl) angles of the isocyanide ligand are nearly linear for the metals in the +2 oxidation state, for which the ligands function essentially as pure donors. The -CN stretching frequencies for these divalent metal isocyanides are at or above that of the free ligand. Relative to FeII, in the structure containing iron in the formally zero-valent oxidation state, the Fe-C bond lengths have shortened, the C N bond lengths have elongated, the (M)C-N-C(Xyl) angles of the terminal CNXyl ligands are more bent, and the -CN stretching frequencies have shifted to lower energies, all indicative of substantial M(d-).- backbonding.
- Brennessel, William W.,Kucera, Benjamin E.,Young, Victor G.,Ellis, John E.
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p. 1118 - 1127
(2019/07/24)
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- Hexafluoroisopropanol as the Acid Component in the Passerini Reaction: One-Pot Access to β-Amino Alcohols
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A new Passerini-type reaction in which hexafluoroisopropanol functions as the acid component is reported. The reaction tolerates a broad range of isocyanides and aldehydes, and the formed imidates can be reduced toward β-amino alcohols under mild and metal-free conditions. In addition, the imidate products were shown to undergo an unprecedented retro-Passerini-type reaction under microwave conditions, providing valuable mechanistic information about the Passerini reaction and its variations.
- Saya, Jordy M.,Berabez, Rayan,Broersen, Pim,Schuringa, Imme,Kruithof, Art,Orru, Romano V. A.,Ruijter, Eelco
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supporting information
p. 3988 - 3991
(2018/07/15)
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- Palladium-Catalyzed One-Pot Synthesis of N -Sulfonyl, N -Phosphoryl, and N -Acyl Guanidines
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An efficient palladium-catalyzed cascade reaction of azides with isonitrile and amines is presented; it offers an alternative facile approach toward N -sulfonyl-, N -phosphoryl-, and N -acyl-functionalized guanidines in excellent yield. These series of substituted guanidines exhibit potential biological and pharmacological activities. In addition, the less reactive intermediate benzoyl carbodiimide could be isolated by silica gel column flash chromatography in moderate yield.
- Qiao, Guanyu,Zhang, Zhen,Huang, Baoliang,Zhu, Liu,Xiao, Fan,Zhang, Zhenhua
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p. 330 - 340
(2018/01/12)
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- Excited-State Switching between Ligand-Centered and Charge Transfer Modulated by Metal-Carbon Bonds in Cyclopentadienyl Iridium Complexes
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Three series of pentamethylcyclopentadienyl (Cp?) Ir(III) complexes with different bidentate ligands were synthesized and structurally characterized, [Cp?Ir(tpy)L]n+ (tpy = 2-tolylpyridinato; n = 0 or 1), [Cp?Ir(piq)L]n+ (piq = 1-phenylisoquinolinato; n = 0 or 1), and [Cp?Ir(bpy)L]m+ (bpy = 2,2′-bipyridine; m = 1 or 2), featuring a range of monodentate carbon-donor ligands within each series [L = 2,6-dimethylphenylisocyanide; 3,5-dimethylimidazol-2-ylidene (NHC); methyl)]. The spectroscopic and photophysical properties of these molecules and those of the photocatalyst [Cp?Ir(bpy)H]+ were examined to establish electronic structure-photophysical property relationships that engender productive photochemical reactivity of this hydride and its methyl analogue. The Ir(III) chromophores containing ancillary CNAr ligands exhibited features anticipated for predominantly ligand-centered (LC) excited states, and analogues bearing the NHC ancillary exhibited properties consistent with LC excited states containing a small admixture of metal-to-ligand charge-transfer (MLCT) character. However, the molecules featuring anionic and strongly σ-donating methyl or hydride ligands exhibited photophysical properties consistent with a high degree of CT character. Density functional theory calculations suggest that the lowest energy triplet states in these complexes are composed of a mixture of MLCT and ligand-to-ligand CT originating from both the Cp? and methyl or hydride ancillary ligands. The high degree of CT character in the triplet excited states of methyliridium complexes bearing C^N-cyclometalated ligands offer a striking contrast to the photophysical properties of pseudo-octahedral structures fac-Ir(C^N)3 or Ir(C^N)2(acac) that have lowest-energy triplet excited states characterized as primarily LC character with a more moderate MLCT admixture.
- Deaton, Joseph C.,Taliaferro, Chelsea M.,Pitman, Catherine L.,Czerwieniec, Rafa?,Jakubikova, Elena,Miller, Alexander J. M.,Castellano, Felix N.
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p. 15445 - 15461
(2019/01/04)
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- TEMPO-Catalyzed Aerobic Oxidative Selenium Insertion Reaction: Synthesis of 3-Selenylindole Derivatives by Multicomponent Reaction of Isocyanides, Selenium Powder, Amines, and Indoles under Transition-Metal-Free Conditions
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A novel and efficient approach for the selenium functionalization of indoles was developed with selenium powder as the selenium source, catalyzed by 2,2,6,6-tetramethylpiperidinooxy (TEMPO) and employing O2 as the green oxidant. This protocol provides a practical route for the synthesis of 3-selenylindole derivatives and has the advantages of readily available starting materials, mild reaction conditions, and a wide scope of substrates. Electron spin-resonance (ESR) studies reveal that the approach involves the formation of nitrogen-centered radicals and selenium radicals via oxidation of in situ generated selenoates.
- Liu, Huan,Fang, Yi,Wang, Shun-Yi,Ji, Shun-Jun
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supporting information
p. 930 - 933
(2018/02/22)
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- Insertion reactions of small unsaturated molecules in the N-B bonds of boron guanidinates
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We report here 1,1- and 1,2-insertion reactions of small unsaturated molecules in the N-B bonds of two boron guanidinates, (Me2N)C(NiPr)2BCy2 (1) and {iPr(H)N}C(NiPr){N(p-tBu-C6H4)}BCy2 (2), and two bisboron guanidinates(2-), {iPr(BCy2)N}C(NiPr){N(p-tBu-C6H4)}BCy2 (3) and {iPr(C8H14B)N}C(NiPr){N(p-Me-C6H4)}BC8H14 (4), the latter being prepared for the first time by double deprotonation of the corresponding guanidine with the 9-borabicyclo[3.3.1]nonane dimer, (H-BC8H14)2. Compounds 1-4 easily insert aromatic isonitriles, XylNC (Xyl = 2,6-Me2-C6H3) and (p-MeO-C6H4)NC, to give the expected diazaboroles 5-12, some of them being structurally characterised by X-ray diffraction. Interestingly, the BC8H14 derivatives 11 and 12 are in a fast temperature-dependent equilibrium with the de-insertion products, whose thermodynamic parameters are reported here. A correlation between these equilibria and the puckered heterocyclic structure found in the solid state for 11, and confirmed by DFT calculations, is also established. Reactions of the aforementioned guanidinates with CO are more sluggish or even precluded, and only one product, {iPr(H)N}C{N(p-tBu-C6H4)}(NiPr)(CO)BCy2 (13), could be isolated in moderate yields. The 1,2-insertions of benzaldehyde in compounds 1, 2 and 4 are reversible reactions in all cases, and only one of the insertion products, {iPr(H)N}C{N(p-tBu-C6H4)}(NiPr)(PhHCO)BCy2 (16a), was isolated and diffractrometrically characterised. Likewise, CO2 reversibly inserts into a N-B bond of 2 to give {iPr(H)N}C{N(p-tBu-C6H4)}(NiPr)(CO2)BCy2 (19) with a conversion of ca. 9%. In all these equilibria, de-insertion is always favoured upon increasing the temperature.
- Ramos, Alberto,Anti?olo, Antonio,Carrillo-Hermosilla, Fernando,Fernández-Galán, Rafael,Montero-Rama, María Del Pilar,Villase?or, Elena,Rodríguez-Diéguez, Antonio,García-Vivó, Daniel
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supporting information
p. 10281 - 10299
(2017/08/15)
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- Aerobic radical-cascade cycloaddition of isocyanides, selenium and imidamides: Facile access to 1,2,4-selenadiazoles under metal-free conditions
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A novel and facile metal-free method for the green synthesis of 1,2,4-selenadiazol-5-amine derivatives through the aerobic radical-cascade multi-component reactions of isocyanides, selenium powder and imidamides is reported herein. O2 in the air was employed as the green oxidant to achieve the cycloaddition with the generation of H2O as the sole by-product. It also features good functional group compatibility and broad substrate scope. In addition, this method was successfully applied to the functionalization of biologically active molecules.
- Fang, Yi,Zhu, Zheng-Lin,Xu, Pei,Wang, Shun-Yi,Ji, Shun-Jun
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supporting information
p. 1613 - 1618
(2017/06/05)
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- Cobalt(II)-Catalyzed Isocyanide Insertion Reaction with Sulfonyl Azides in Alcohols: Synthesis of Sulfonyl Isoureas
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A Co(II)-catalyzed isocyanide insertion reaction with sulfonyl azides in alcohols to form sulfonyl isoureas via nitrene intermediate has been developed. This protocol provides a new, environmentally friendly, and simple strategy for the synthesis of sulfonyl isourea derivatives by employing a range of substrates under mild conditions.
- Jiang, Tian,Gu, Zheng-Yang,Yin, Ling,Wang, Shun-Yi,Ji, Shun-Jun
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supporting information
p. 7913 - 7919
(2017/08/14)
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- Facile access to a Ge(II) dication stabilized by isocyanides
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Herein, we introduce isocyanide as a ligand in main group chemistry and describe the facile isolation of a Ge(ii) dication. The reaction of 2,6-dimethylphenylisocyanide with GeCl2 leads to the formation of a Ge(ii) dication with two [GeCl3]- molecules as counter anions. The dicationic Ge(ii) center is bound to four isocyanide ligands and also holds a lone pair of electrons. DFT calculations reveal that the dication is stabilized only by σ-donation from the four isocyanide ligands. Natural population analysis gives a charge of +0.74 on the Ge(ii) center, indicating that the positive charge is shared by the isocyanide substituents.
- Swamy,Yadav, Sandeep,Pal, Shiv,Das, Tamal,Vanka, Kumar,Sen, Sakya S.
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p. 7890 - 7892
(2016/07/06)
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- Comparative measure of the electronic influence of highly substituted aryl isocyanides
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To assess the relative electronic influence of highly substituted aryl isocyanides on transition metal centers, a series of C4v-symmetric Cr(CNR)(CO)5 complexes featuring various alkyl, aryl, and m-terphenyl substituents have been prepared. A correlation between carbonyl-ligand 13C{1H} NMR chemical shift (δCO) and calculated Cotton-Kraihanzel (C-K) force constant (kCO) is presented for these complexes to determine the relative changes in isocyanide σ-donor/π-acid ratio as a function of substituent identity and pattern. For nonfluorinated aryl isocyanides possessing alkyl or aryl substitution, minimal variation in effective σ-donor/π-acid ratio is observed over the series. In addition, aryl isocyanides featuring strongly electron-releasing substituents display an electronic influence that nearly matches that of nonfluorinated alkyl isocyanides. Lower σ-donor/π-acid ratios are displayed by polyfluorinated aryl isocyanide ligands. However, the degree of this attenuation relative to nonfluorinated aryl isocyanides is not substantial and significantly higher σ-donor/π-acid ratios than CO are observed in all cases. Substituent patterns for polyfluorinated aryl isocyanides are identified that give rise to low relative σ-donor/π-acid ratios but offer synthetic convenience for coordination chemistry applications. In order to expand the range of available substitution patterns for comparison, the syntheses of the new m-terphenyl isocyanides CNArTripp2, CNp-MeArMes2, CNp-MeArDArF2, and CNp-FArDArF2 are also reported (ArTripp2 = 2,6-(2,4,6-(i-Pr)3C6H2)2C6H3); p-MeArMes2 = 2,6-(2,4,6-Me3C6H2)2-4-Me-C6H2); p-MeArDArF2 = 2,6-(3,5-(CF3)2C6H3)2-4-Me-C6H2); p-FArDArF2 = 2,6-(3,5-(CF3)2C6H3)2-4-F-C6H2).
- Carpenter, Alex E.,Mokhtarzadeh, Charles C.,Ripatti, Donald S.,Havrylyuk, Irena,Kamezawa, Ryo,Moore, Curtis E.,Rheingold, Arnold. L.,Figueroa, Joshua S.
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p. 2936 - 2944
(2015/03/30)
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- Palladium-catalyzed cross-coupling reaction of azides with isocyanides
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An efficient palladium-catalyzed cross-coupling reaction of azides with isocyanides is developed, providing a general synthetic route to unsymmetric carbodiimides with excellent yields. This method shows a broad substrate scope, including not only aryl azides, but also unactivated benzyl and alkyl azides. Furthermore, from readily available substrates, Pd-catalyzed coupling with a tandem amine insertion cascade to obtain unsymmetric trisubstituted guanidines has been achieved in a one-pot fashion.
- Zhang, Zhen,Li, Zongyang,Fu, Bin,Zhang, Zhenhua
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p. 16312 - 16315
(2015/11/16)
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- Acyclic aminocarbene-like palladium complex-catalyzed Suzuki-Miyaura reaction at low catalyst loadings
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A series of air-stable aminocarbene-like palladium(II) complexes were easily prepared by the reaction of bis-aromaticisocyanide-dichloropalladium(II) with N-arylbenzamidines. 0.1 mol % of the optimal palladium complex 3a showed excellent catalytic activity for Suzuki-Miyaura cross-coupling reaction at room temperature and the desired products were isolated in up to 98% yields. Moreover, a large-scale reaction showed that 0.01 mol % 3a was enough to catalyze the coupling reaction efficiently at room temperature to give the desired product in 93% yield.
- Fang, Yi,Wang, Shun-Yi,Ji, Shun-Jun
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p. 9679 - 9683
(2015/12/04)
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- Synthesis of isonitriles from N-substituted formamides using triphenylphosphine and iodine
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Treatment of N-substituted formamides with the reagent combination of triphenylphosphine and molecular iodine, in the presence of a tertiary amine, quickly produces the corresponding isocyanides in high yields under ambient conditions. The process employs readily available and low-cost reagents, a convenient synthetic procedure, and mild reaction conditions for the synthesis of various alkyl and aryl isocyanides.
- Wang, Xia,Wang, Qing-Gang,Luo, Qun-Li
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- C-F Activation in Perfluorinated Arenes with Isonitriles under UV-Light Irradiation
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Due to the great value of fluorinated arenes in agrochemistry, medicinal chemistry and materials science, development of methods for preparation of fluorinated arenes is of high importance. They can be either accessed by arene fluorination or by partial arene defluorination. However, the carbon-fluorine bond belongs to the strongest σ-bonds, which renders C-F activation highly challenging. Here it is shown that aryl and alkyl isonitriles efficiently activate the strong C-F bond in perfluoroarenes by simple UV irradiation under mild conditions. Reactions proceed by formal direct insertion of the isonitrile into the C-F bond without any transition metal. Activation occurs at arene C-F bonds whereas aliphatic C-F bonds remain unreacted. For selected perfluoroarenes C-F activation occurs with high regioselectivity and resulting imidoyl fluorides are transformed into other valuable compounds. Theoretical studies give insights into the reaction mechanism.
- Dewanji, Abhishek,Mück-Lichtenfeld, Christian,Bergander, Klaus,Daniliuc, Constantin G.,Studer, Armido
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supporting information
p. 12295 - 12298
(2015/08/25)
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- Isocyanide-based multicomponent reactions: Concise synthesis of spirocyclic oxindoles with molecular complexity by using a [1,5]-hydrogen shift as the key step
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A concise multicomponent reaction of isocyanide, α-substituted allenoate, and methyleneindolinone has been disclosed. This protocol provides a fast and straightforward approach to synthesize unusual tricyclic oxindoles in an efficient and atom-economic manner. Mechanistically, the present cycloaddition may proceed through a cascade sequence involving double Michael addition, double cyclization, double [1,5]-hydrogen shift, and group migration. The introduction of a special alkyl group to the allenoate is believed to play a key role in the cascade reaction. This method also features a broad substrate scope, which is particularly useful for the delivery of a large number of compounds. Shift your perspective! An unprecedented cascade reaction, under mild conditions, involving a double Michael addition, double cyclization, and double [1,5]-hydrogen shift, followed by group migration is disclosed. This reaction offers a fast and straightforward approach to unusual polycyclic spirooxindoles (see scheme).
- Su, Shikuan,Li, Chunju,Jia, Xueshun,Li, Jian
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p. 5905 - 5909
(2014/05/20)
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- Synthesis and reactivity of titanium hydrazido complexes supported by diamido-ether ligands
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The synthesis and reactivity of titanium diphenyl hydrazido(2-) complexes supported by the diamido-ether ligands O(2-C6H4NSiMe 3)2 (N2ArO) and O(CH 2CH2NSiMe3)2 (N2O) are described. Reaction of Li2N2ArO or Li 2N2O with Ti(NNPh2)Cl2(py) 3 afforded Ti(N2ArO)(NNPh2)(py) 2 (14) or Ti(N2O)(NNPh2)(py)2 (15) with κ3-mer-bound diamido-ether ligands. Reaction with tBu-bipy (4,4′-di-tert-butyl-2,2′-bipyridyl) or bipy (2,2′-bipyridyl) gave a switch to κ3-fac-coordination. Reaction of 15 with Ar′NCO (Ar′ = 2,6-C6H 3iPr2) gave Ti{O(CH2CH 2NSiMe3)(CH2CH2NC(O)N(SiMe 3)Ar′)}-{N(NPh2)C(O)N(Ar′)}, in which the substrate has inserted into a Ti-Namide bond of N2O as well as adding to the Ti=Nα multiple bond. With Ar′NCS the [2+2] cycloaddition product Ti(N2O){N(NPh2) C(NAr′)S}(py) was obtained, and with Ar′NCSe a mixture was formed including Ti2(N2O)2(μ-Se)2. Both 14 and 15 reacted with ArFxCN (ArFx = C6H 3F2 or C6F5) to give Ti=N α bond insertion products of the type Ti(L){NC(Ar Fx)NNPh2}(py)2 (L = N2ArO or N2O) containing hydrazonamide ligands. Reaction of 14 with XylNC (Xyl = 2,6-C6H3Me2) gave only the isonitrile σ-adduct Ti(N2ArO)(NNPh2)(py)(CNXyl), whereas 15 underwent Nα-Nβ bond reductive cleavage with tBuNC or XylNC forming Ti(N2O)(NPh 2)(NCNtBu) or Ti{O(CH2CH2NSiMe 3)(CH2CH2NCN(SiMe3)Xyl)}(NPh 2)(NCNXyl) (27). Both contain metalated carbodiimide ligands, but in 27 an additional reaction of XylNC with the Ti-Namide bond of N 2O has taken place. Compound 15 also reacted with a number of internal alkynes RCCR′ (R = R′ = Me or Ph; R = Me, R′ = aryl) to give Nα-Nβ bond reductive cleavage products of the type Ti{O(CH2CH2NSiMe3)(CH 2CH2NC(R)C(R′)NSiMe3}(NPh2), again involving a reaction of a Ti-Namide bond.
- Unruangsri, Junjuda,Morgan, Hannah,Schwarz, Andrew D.,Schofield, A. Daniel,Mountford, Philip
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p. 3091 - 3107
(2013/06/27)
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- Efficient one-pot synthesis of unsymmetrical gold(I) N-heterocyclic carbene complexes and their use as catalysts
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Eleven different gold(I) complexes of new NHC ligands were prepared in excellent yield, demonstrating the versatility of the new route to NHC complexes. While the influence of electronically different ligands on the synthesis of the catalysts was small, the catalytic activities of the products differed significantly.
- Hashmi, A. Stephen K.,Yu, Yang,Rominger, Frank
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p. 895 - 904
(2012/04/04)
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- Multicomponent reaction to construct spirocyclic oxindoles with a Michael (triple Michael)/cyclization cascade sequence as the key step
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Multicomponent cycloadditions with readily available isocyanides, allenoates, and isatylidene malononitriles are disclosed. This reaction, which does not require the aid of any catalyst, allows the efficient syntheses of spirocyclic oxindoles with excellent regioselectivity. Reactions with ethyl 2,3-butadienoate and various structurally diverse α- and γ-substituted allenoates are also fully explored. Remarkably, we have shown that the usual three-component process can be further developed into an unprecedented four-component cycloaddition in the presence of water, which provides a new strategy to access highly unusual tricyclic oxindoles. From a synthetic point of view, this protocol is very interesting considering the high level of complexity reached in one step. The mechanism is thought to proceed by a triple Michael/cyclization process by using allenoate as a three carbon atom component (3 C). Furthermore, multicomponent reaction with γ-substituted allenoate also results in a very interesting conversion. In such cases, the unusual cleavage of the "C=C" double bond of isatylidene malononitrile and one of the "C=C" double bonds of allenoate is always observed. Multiply your chemistry! Multicomponent reactions with readily available isocyanides, allenoates, and isatylidene malononitriles are disclosed. This protocol provides a synthetic route to an exocyclic double bond containing a spirocyclic ring in an efficient manner with excellent regioselectivity (see scheme). Copyright
- Li, Jian,Wang, Ning,Li, Chunju,Jia, Xueshun
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p. 9645 - 9650
(2012/09/07)
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- Isocyanide-based multicomponent [2+2+1]-cycloaddition strategy to construct functionalized spirocyclic oxindoles
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Isocyanide-based three-component [2+2+1]-cycloaddition reactions from isocyanides, activated alkynes, and isatylidene malononitriles were investigated to provide a new access to spirocyclic oxindole with five-membered carbon rings. The displacement of isatylidene malononitrile with oxindolylideneacetate essentially results in opposite regioselectivity, which adds to its attractiveness. Georg Thieme Verlag Stuttgart ? New York.
- Jie, Haohua,Li, Jian,Li, Chunju,Jia, Xueshun
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p. 2274 - 2278
(2012/10/29)
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- Palladium-catalyzed cascade process consisting of isocyanide insertion and benzylic C(sp3)-H activation: Concise synthesis of indole derivatives
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Synthesis of the indole skeleton was achieved using a Pd-catalyzed cascade process consisting of isocyanide insertion and benzylic C(sp3)-H activation. It was found that slow addition of isocyanide is effective for reducing the amount of catalyst needed and Ad2PnBu is a good ligand for C(sp3)-H activation. The construction of the tetracyclic carbazole skeleton was also achieved by a Pd-catalyzed domino reaction incorporating alkyne insertion.
- Nanjo, Takeshi,Tsukano, Chihiro,Takemoto, Yoshiji
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supporting information; experimental part
p. 4270 - 4273
(2012/10/08)
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- Silver hexafluoroantimonate-catalyzed three-component [2+2+1]cycloadditions of allenoates, dual activated olefins, and isocyanides
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The intermolecular [2+2+1]multicomponent cycloadditions from readily available allenoates, dual activated olefins and isocyanides catalyzed by silver hexafluoroantimonate were studied. This protocol allowed the syntheses of highly functionalized five-membered carbocycles with exclusive regioselectivity and stereoselectivity in an efficient and atom-economical manner.
- Li, Jian,Liu, Yuejin,Li, Chunju,Jia, Xueshun
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p. 913 - 917
(2011/06/18)
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- Syntheses of spirocyclic oxindole-butenolides by using three-component cycloadditions of isocyanides, allenoates, and isatins
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Spiro workflow! Efficient syntheses of spirocyclic oxindole-butenolides from readily available isocyanides, allenoates, and isatins are disclosed (see scheme; R1=alkyl, aryl; R2=halide, nitro, methoxy; PG=protecting group). This protocol also allows the insertion of carbon monoxide into organic molecules without the aid of a transition-metal catalyst after the hydrolysis process. Copyright
- Li, Jian,Liu, Yuejin,Li, Chunju,Jia, Xueshun
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p. 7409 - 7413
(2011/08/05)
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- A complex of gold(I) benzenethiolate with isocyanide: Synthesis and crystal and molecular structures
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2,6-Dimethylphenyl isocyanide forms complexes with gold(I) chloride (complex 4) and gold(I) benzenethiolate (complex 5) but forms no stable complexes with gold alkanethiolates. A reaction of complex 5 with tetramethylthiuram disulfide yields gold(I) dimethyldithiocarbamate. Stable gold(III) derivatives cannot be obtained in such a way. Shortened intermolecular Au...Au contacts in complexes 4 and 5 (X-ray diffraction) suggest the presence of "aurophilic" interactions in them.
- Dyadchenko,Belov,Dyadchenko,Slovokhotov,Banaru,Lemenovskii
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experimental part
p. 539 - 543
(2011/02/16)
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- Lewis acid-promoted imine synthesis by the insertion of isocyanides into C-H bonds of electron-rich aromatic compounds
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The Lewis acid-promoted insertion of isocyanides into aromatic C-H bonds is reported. An imine functionality containing an array of N-substituents can be introduced directly into electron-rich aromatics in good yields.
- Tobisu, Mamoru,Yamaguchi, Seiji,Chatani, Naoto
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p. 3351 - 3353
(2008/02/12)
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- Synthesis of novel heterocyclic structures via reaction of isocyanides with S-trans-enones
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The reaction of enone 1, bearing an internal nucleophilic moiety, i.e., furan or pyrrole (X = O, NR′), with isocyanides is presented. The formation of products resulting from the reaction of the zwitterionic intermediate 2 with a second equivalent of isocyanide prior to cyclization to give 3, as well as the direct formation of 4 from 2, is described.
- Winkler, Jeffrey D.,Asselin, Sylvie M.
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p. 3975 - 3977
(2007/10/03)
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- Controlled nucleophilic activation of different sites in [Mo 2Cp2L2(μ-SMe)2(μ-L′)] + cations (L = ButNC, xylNC, CO; L′ = SMe or PPh2)
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The thiolato-bridged binuclear molybdenum complexes [Mo2Cp 2L2(μ-SMe)2(μ-L′)]Y (Cp = η5-C5H5; L′ = SMe, L = Bu tNC (1a), xylNC (1b) or CO (3); L′ = PPh2, L = ButNC (16); Y = BF4, Cl) react with the anionic reagents NaBH4, NaBD4, LiR (R = Me, Bun), R′MgCl (R′ = Me, Pri, Bun or Ph). The products are unsubstituted (5, 7) or substituted (8-12) η4-cyclopentadiene derivatives, [Mo2(η5-C5H 5)(η4-C5H5R)L 2(μ-SMe)3] (L = xylNC, CO), or μ-formimidoyl dinuclear products, [Mo2Cp2L2(μ-SMe) 2(μ-L′)(μ-CHNR)] (L′ = SMe, L = ButNC (4) or xylNC (6); L′ = PPh2, L = ButNC (17)). Since the reduced dinuclear species [Mo2Cp2(CO) 2(μ-SMe)2] and the related oxo-compound [Mo 2Cp2(CO)(O)(μ-SMe)2] are sometimes isolated as minor products, the anionic reagent can play a secondary role as a reductant in these reactions in addition to its main role as a nucleophile. The electronic properties of the donor carbon atoms of the cyclopentadienyl rings and of the terminal ligands L, together with the nature of the anionic reagent, are the dominant factors controlling selective formation of 4-12 and 17. Tetrafluoroboric acid reacts with the substituted cyclopentadiene derivatives 9, 11 and 12 to form new functionalised cyclopentadienyl derivatives, [Mo 2(η5-C5H5)(η5- C5H4R)(CO)2(μ-SMe)3](BF 4) (R = Me (13), Bun (14) or Ph (15)). New complexes have been characterised by spectroscopic and chemical methods, supplemented for 5, 6 and 12 by X-ray diffraction studies at 100 K.
- Cabon, Nolwenn,Pétillon, Fran?ois Y.,Orain, Pierre-Yves,Schollhammer, Philippe,Talarmin, Jean,Muir, Kenneth W.
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p. 4583 - 4601
(2007/10/03)
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- A polymer-supported [1,3,2]oxazaphospholidine for the conversion of isothiocyanates to isocyanides and their subsequent use in an ugi reaction.
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The design and synthesis of a new polymer supported reagent for the clean conversion of isothiocyanates to isocyanides under microwave conditions was accomplished. The structurally diverse isocyanides generated were used in an Ugi 3CC, allowing the rapid generation of 2-isoindolinone-7-carboxamide analogues.
- Ley, Steven V,Taylor, Stephen J
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p. 1813 - 1816
(2007/10/03)
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- Iminoacylberyllium compounds derived from octamethyl- and decamethylberyllocene and 2,6-dimethylphenyl isocyanide. Evidence for the existence of η5/η1 isomers of beryllocenes
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The existence in solution of η5/η1 isomers of the beryllocenes Be(C5Me5)2 and Be(C5Me4H)2 is inferred from the results of their reaction with CNXyl to give iminoacyl products. The process is reversible and involves coupling of a Be-η1-Cp′ group with the isocyanide.
- Del Mar Conejo,Fernández, Rafael,Carmona, Ernesto,Gutiérrez-Puebla, Enrique,Monge, ángeles
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p. 2434 - 2436
(2008/10/08)
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- Reaction of 2,6-xylyl isoselenocyanate with organolithium compounds
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Reaction of 2,6-xylyl isoselenocyanate (1) with organolithium compounds was examined focussing on the site selectivities. Phenyllithium attacked selenium exclusively whereas some benzylic organolithiums reacted at the central carbon of 1 to afford the corresponding lithium selenocarboximidates. Phenylethynyllithium and (t)BuLi gave mixtures of the carbophilic and selenophilic products. The lithium enolate of isobutyrophenone reacted with 1 at both its C- and O-nucleophilic centers attacking the central carbon of 1. By the alkylation of lithium selenocarboximidates formed from 1 and benzylic organolithiums, several selenoimidates were synthesized.
- Maeda, Hajime,Kambe, Nobuaki,Sonoda, Noboru,Fujiwara, Shin-Ichi,Shin-Ike, Tsutomu
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p. 12165 - 12176
(2007/10/03)
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- The Roles of Aminocarbyne Intermediates and Intramolecular Electron Transfer in the Formation od Carbon-Carbon Bonds by the Coupling of Isocyanides
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The binuclear iridium complex Ir2(CNR)4(dmpm)2, 1, (R = 2,6-Me2C6H3, dmpm = Me2PCH2PMe2) was prepared by reduction of 2 with Na amalgam in benzene.The structure of 1, determined by X-ray diffraction, consists of two iridium atoms bridged by two cis,cis dmpm ligands and two μ-2,6-xylyl isocyanide ligands.The Ir-Ir bond length is 2.5998 (7) Angstroem.The nonbonded distance between the carbon atoms of the μ-isocyanide ligands is 2.37 (2) Angstroem.The potential coupling of the two μ-isocyanide ligands of 1, promoted by Lewis acids, wasinvestigated.Addition of 2 equiv of BH3*THF to 1 affords Ir2(μ-CN(BH3)R)2(CNR)2(dmpm)2, 2, which contains two μ-CN(BH3)R aminocarbyne groups which are not coupled.Addition of Al2Et6 to 1 in toluene gives Ir2(C2(NR)2AlEt2)(CNR)2(dmpm)2, 3, which contains a new carbon-carbon bond, d(C-C) = 1.48 (1) Angstroem, between two coupled isocyanides.The AlEt2 fragment bridges two isocyanide N atoms to form an essentially planar five-membered C2N2Al ring.The C2N2Al ring is coplanar with the two iridium atoms.Complex 3 is paramagnetic and exhibits an isotropic EPR powder spectrum, g = 2.005 at -150 deg C.Complex 3 is reversibly oxidized electrochemically to form the diamagnetic species (CNR)2(dmpm)2>, 4.E1/2(4/3) = -0.22 V vs SCE.The mechanism of isocyanide coupling leading to 3 involves electronic reconfiguration of the d9-d9 Ir02 core of 1 to the d8-d8 IrI2 "A-frame" species 4.Paramagnetic 3 is formed by single-electron transfer to 4 by AlEt4(-), formed in situ during isocyanide coupling.Crystal data for 1: space group P21; a = 10.615 (2), b = 16.883 (3), c = 15.044 (3) Angstroem; β = 94.23 (1)0; V = 2689 (2) Angstroem3; Z = 2; R = 0.033, Rw = 0.044 for 528 variables and 3229 unique data with I > 3?(I), Mo Kα radiation.Crystal data for 2: space group P21212; a = 15.905 (2), b = 16.286 (2), c = 10.528 (3) Angstroem; Z = 2; V = 2727 (1) Angstroem3; R = 0.048, Rw =0.062 for 282 variables and 2263 unique data with I > 3?(I), Mo Kα radiation.Crystal data for 3: space group P21/c; a = 11.44 (1), b = 19.072 (1), c = 25.602 (3) Angstroem; β = 102.910; V = 5446 (2) Angstroem3; Z = 4; R = 0.035, Rw = 0.040 for 550 variables and 5330 unique data with I > 3?(I), Mo Kα radiation.
- Wu, Jianxin,Fanwick, Phillip E.,Kubiak, Clifford P.
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p. 7812 - 7823
(2007/10/02)
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- Reactions of metallocene niobium(III) isocyanide complexes with oxidizing reagents
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New dicyclopentadienylniobium(III) complexes have been made by reducing NbCp2Cl2 (Cp=η5-C5H5, η5-C5H4SiMe3 and η5-C5H3(SiMe3)2) with Na/Hg in the presence of isocyanides CNR (R=Bun, But, Ph and 2,6-Me
- Gomez, Manuel,Ilarduya, Jesus M. Martinez de,Royo, Pascual
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p. 197 - 204
(2007/10/02)
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- iron(II) Compounds with Isocyanides as Axial Ligands
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Aliphatic and aromatic monodentate isocyanides RNC (R = t-Bu, c-Hx, substituted Ph) react with iron(II) (TPyPFe) to form the corresponding diaxially substituted iron(II) compounds TPyPFe(RNC)2 1a-8a.The spectroscopic data and thermal properties of the complexes are described and compared with the analogous PcFe(CNR)2 compounds 1b-8b.
- Hanack, Michael,Thies, Ruediger
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p. 1225 - 1230
(2007/10/02)
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- Ring Closure of ortho-Blocked 4-Aryl-1,2,4-triaza-1,3-dienes via 1,6-Electrocyclisation followed by Diels-Alder Dimerisation
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1-Acyl-4-(2,6-dimethylphenyl)-1,2,4-triaza-1,3-dienes (7), generated in situ upon manganese dioxide oxidation of the corresponding N-acyl-N'-(2,6-dimethylphenylaminomethylene)hydrazines (6), give the bridged heterocyclic compounds (10) via 1,6-electrocyclisation followed by Diels-Alder dimerisation.The isonitrile (8) is also obtained as a minor fragmentation product.
- Trave, Roberto,Garanti, Luisa,Zecchi, Gaetano
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p. 1533 - 1536
(2007/10/02)
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- Isonitriles as herbicide extenders
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Herbicidally active thiolcarbamates are employed in combination with certain substituted phenyl isonitriles having the formula STR1 in which R1 is selected from the group consisting of C1 -C6 alkyl, C1 -C6 alkoxy, C1 -C6 alkylthio, phenyl, halogen, benzylthio, and p-chlorobenzylthio, and R2 is selected from the group consisting of hydrogen, C1 -C6 alkyl, C1 -C6 alkoxy, and halogen. In a typical application, the isonitrile is included in sufficient quantity to lessen the rate of soil degradation of the thiolcarbamate. As a result, the herbicidal effectiveness of the thiolcarbamate is enhanced and prolonged, rendering a single application of the herbicide effective over a longer period of time.
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- Catalysed and Non-catalysed Reaction Between and Isonitriles
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The reaction between and isonitrile, RNC, is catalysed by CoCl2*H2O and readily yields the complexes (n = 1-3, R = Me, C6H11, tBu, PhCH2, Ph, 2,6-Me2C6H3, or 2,4,6-Me3C6H2; n = 4, R = tBu; n = 4 or 5, R = Ph, 2,6-Me2C6H3, or 2,4,6-Me3C6H2).The high-yield synthesis of from and RNC in the absence of catalyst is also reported.Trimethylamine N-oxide has been used to synthesize from and RCN and results are compared with the CoCl2 catalysed reaction.All products were characterized by i.r. and n.m.r. spectroscopy.The higher substituted derivatives were further characterized by reaction with I2 and tetracyanoethylene (tcne) and gave (n = 2, R = tBu, PhCH2, or 2,6-Me2C6H3; n = 3, R = tBu or 2,6-Me2C6H3; n = 4, R = 2,6-Me2C6H3) and cis- and trans- from appropriate starting materials.Mechanistic data suggest that the reaction occurs via attack of catalyst at a co-ordinated CO ligand.Subsequent attack by unco-ordinated RNC in an intermolecular, non-bridging mechanism leads to the required isonitrile derivatives.
- Albers, Michel O.,Coville, Neil J.,Singleton, Eric
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p. 1069 - 1080
(2007/10/02)
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- 1,3-Acyl Migration in Carbonic Acid Derivatives - Synthesis of S-Polyhalogenoalkyl N-Acyl-N-aryl(alkyl)thiocarbamates
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Aryl(alkyl)iminochloromethyl polyhalogenoalkyl sulphides react with carboxylic acids to give S-polyhalogenoalkyl N-acyl-N-aryl(alkyl)thiocarbamates, which have not been synthesized by other routes.By analogy with known 1,3 rearrangements, the reaction appears to involve a nucleophilic substitution followed by a new type of 1,3-acyl migration.Similarly, with sodium azide 1-methyl- and 1-phenyl-5-trichloromethylthiotetrazoles are also obtained.
- Galli, Remo,Palla, Ottorino,Gozzo, Franco
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p. 2813 - 2818
(2007/10/02)
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