- Synthesis, Structure, and Photophysical Properties of Mo2(NN)4 and Mo2(NN)2(TiPB)2, Where NN = N,N′-Diphenylphenylpropiolamidinate and TiPB = 2,4,6-Triisopropylbenzoate
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Two dimolybdenum compounds featuring amidinate ligands with a bond, Mo2(NN)4 (I), where NN = N,N′-diphenylphenylpropiolamidinate, and trans-Mo2(NN)2(TiPB)2 (II), where TiPB = 2,4,6-triisopropylbenzoate, have been prepared and structurally characterized by single-crystal X-ray crystallography. Together with Mo2(DAniF)4 (III), where DAniF = N,N′-bis(p-anisyl)formamidinate, all three compounds have been studied with steady-state UV-vis, IR, and time-resolved spectroscopy methods. I and II display intense metal to ligand charge transfer (MLCT). Singlet state (S1) lifetimes of I-III are determined to be 0.7, 19.1, and 2.0 ps, respectively. All three compounds have long-lived triplet state (T1) lifetimes around 100 μs. In femtosecond time-resolved infrared (fs-TRIR) experiments, one band is observed at the S1 state for I but two for II, which indicate different patterns of charge distribution. The electron would have to be localized on one NN ligand in I and partially delocalized over two NN ligands in II to account for the observations. The result is a standard showcase of excited-state mixed valence in coordination compounds.
- Jiang, Changcheng,Young, Philip J.,Durr, Christopher B.,Spilker, Thomas F.,Chisholm, Malcolm H.
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Read Online
- Probing Interligand Electron Transfer in the 1MLCT S1 Excited State of trans-Mo2L2L′2 Compounds: A Comparative Study of Auxiliary Ligands and Solvents
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The interligand charge dynamics of the lowest singlet metal-to-ligand charge-transfer states (1MLCT S1 states) of a series of quadruply bonded trans-Mo2(NN)2(O2C-X)2 paddlewheel compounds are investigated, where NN is a π-accepting phenylpropiolamidinate ligand and O2C-X (X = Me, tBu, TiPB, or CF3) is an auxiliary carboxylate ligand. The compounds show strong light absorption in the visible region due to MLCT transitions from the Mo2 center to the NN ligands. The transferred electron density was followed by femtosecond time-resolved infrared (fs-TRIR) spectroscopy with vibrational reporters such as the ethynyl groups on the NN ligands. The observed fs-TRIR spectra show that these compounds have asymmetric 1MLCT S1 excited states where the transferred electron mainly resides on a single NN ligand. The presence of interligand electron transfer (ILET) is suggested to explain the shape of the ν(C=C) bands and the influence of auxiliary ligands and solvents on the interligand electronic coupling. The ILET in the 1MLCT S1 state is shown to be sensitive to the functional groups on the auxiliary ligands while being less responsive to changes in solvents.
- Jiang, Changcheng,Young, Philip J.,Brown-Xu, Samantha E.,Kender, William T.,Hamilton, Ewan J. M.,Gallucci, Judith C.,Chisholm, Malcolm H.
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Read Online
- Synthesis of 1,4-diphenyl-3-phenylimino-1,2-dihydro-1,2,4-triazolium hydroxide (nitron)
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1,4-Diphenyl-3-phenylimino-1,2-dihydro-1,2,4-triazolium hydroxide (Nitron) is prepared by the reaction of Pb3O4 with diphenylthiourea, followed by the reaction of the obtained diphenylcarbodiimide with phenylhydrazine to form triphenylaminoguanidine, whose heterocyclization yields 1,4-diphenyl-3-phenyl-imino-1,2-dihydro-1,2,4-triazole, which is subsequently oxidized. Pleiades Publishing, Inc., 2006.
- Kriven'ko,Morozova
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Read Online
- Synthesis and Properties of N,N′-Disubstituted Ureas and Their Isosteric Analogs Containing Polycyclic Fragments: XI. 1-[(Adamantan-1 yl)alkyl]-3-arylselenoureas
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Abstract: A series of N,N′-disubstituted selenoureas containing an adamantane fragmenthave been synthesized in 23–75% yields. Procedures for the isolation andpurification of aromatic isoselenocyanates have been improved. The chemicalshift of the C=Se carbon nucleus in the 13C NMRspectra of selenoureas has been refined. The synthesized selenoureas have beenfound to be promising as inhibitors of not only epoxide hydrolase (sEH-H) butalso phosphatase domains (sEH-P) of human soluble epoxide hydrolase.
- Kuznetsov, Ya. P.,Rasskazova,Pitushkin,Eshtukov,Vasipov,Burmistrov,Butov
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p. 1036 - 1046
(2021/09/08)
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- A Mild Photocatalytic Synthesis of Guanidine from Thiourea under Visible Light
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In this work, we developed the catalytic guanylation of thiourea using Ru(bpy)3Cl2 as a photocatalyst under irradiation by visible light. The conversion of various thioureas to the corresponding guanidines was achieved using 1-5 mol % of photocatalyst in a mixture of water and ethanol at room temperature. Key benefits of this reaction include the use of photoredox catalyst, low-toxicity solvents/base, ambient temperature, and an open-flask environment.
- Saetan, Trin,Sukwattanasinitt, Mongkol,Wacharasindhu, Sumrit
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supporting information
p. 7864 - 7869
(2020/11/02)
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- Synthesis of 1,2,4-oxadiazolidines via [3+2] cycloaddition of nitrones with carbodiimides
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An efficient [3+2] cycloaddition of nitrones and carbodiimides has been developed. This 1,3-dipolar cycloaddition features high regioselectivity, mild and metal-free conditions, excellent functional group compatibility, and a broad substrate scope. The X-ray structures of two regio-isomers confirmed the regioselectivity of this transformation.
- Chen, Yuan,Fuyue, Liuting,Wang, Gangqiang,Wang, Hang,Lu, Chun,Guo, Haibing,St. Amant, Chiara,Sun, Shaofa,Xing, Yalan
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supporting information
p. 4329 - 4332
(2019/03/19)
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- A facile method for the preparation of carbodiimides from thioureas and (Boc)2O
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A concise method for the preparation of carbodiimides from thioureas using di-tert-butyl dicarbonate [(Boc)2O] as the dehydrosulfurizative reagent has been developed. Using DMAP as the catalyst, a variety of symmetric and asymmetric 1,3-diaryl thioureas were converted into the corresponding carbodiimides efficiently in a short time.
- Wu, He,Sun, Yan-Fang,Zhang, Chen,Miao, Chun-Bao,Yang, Hai-Tao
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supporting information
p. 739 - 742
(2018/01/27)
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- Copper-catalyzed domino reaction of carbodiimides and benzoic acid derivatives for the synthesis of quinazolinediones
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Quinazolinediones were obtained from 2-iodobenzoic acids and carbodiimide derivatives under mild reaction conditions via a copper-catalyzed domino reaction. The absence of an external base was essential to avoid the generation of amide by-products. Both alkyl- and aryl-substituted carbodiimides gave the corresponding quinazolinediones. However, the use of aryl-substituted carbodiimides resulted in low yields due to an undesired elimination process.
- Duangjan, Chanikan,Rukachaisirikul, Vatcharin,Saithong, Saowanit,Kaeobamrung, Juthanat
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supporting information
p. 3537 - 3540
(2018/08/29)
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- RE[N(SiMe3)2]3-Catalyzed Guanylation/Cyclization of Amino Acid Esters and Carbodiimides
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The example of rare-earth metal-catalyzed guanylation/cyclization of amino acid esters and carbodiimides is well-established, forming 4(3H)-2-alkylaminoquinazolinones in 65-96% yields. The rare-earth metal amides RE[N(TMS)2]3 (RE = Y, Yb, Nd, Sm, La; TMS = SiMe3) showed high activities, and La[N(TMS)2]3 performed best for a wide scope of the substrates.
- Lu, Chengrong,Gong, Chao,Zhao, Bei,Hu, Lijuan,Yao, Yingming
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p. 1154 - 1159
(2018/02/10)
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- Sequential Pd(0)/Fe(III) Catalyzed Azide-Isocyanide Coupling/Cyclization Reaction: One-Pot Synthesis of Aminotetrazoles
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A rapid and efficient synthesis of aminotetrazole from aryl azides, isocyanides, and TMSN3 is developed. The reaction is promoted by sequential Pd(0)/Fe(III) catalysis. The reaction sequence utilizes the Pd-catalyzed azide-isocyanide denitrogenative coupling reaction to generate unsymmetric carbodiimide in situ, which reacts with TMSN3 in the presence of FeCl3 in a single pot. The methodology has distinct advantages over traditional synthetic approaches where toxic Hg and Pb salts are employed at stoichiometric scale.
- Pathare, Ramdas S.,Ansari, Arshad J.,Verma, Sarika,Maurya, Anand,Maurya, Antim K.,Agnihotri, Vijai K.,Sharon, Ashoke,Pardasani, Ram T.,Sawant, Devesh M.
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supporting information
p. 9530 - 9537
(2018/08/03)
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- Ultrasonic-assisted synthesis of carbodiimides from N,N′-disubstituted thioureas and ureas
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A facile and efficient sonochemical method for the preparation of carbodiimides from their corresponding thioureas or ureas was described. Using Ph3P–I2 combination in the presence of triethylamine, various diaryl, aryl–alkyl, as well as dialkyl substituted substrates could be converted into carbodiimides in good-to-excellent yields within short reaction times under mild conditions with simple experimental setup. Graphical abstract: [Figure not available: see fulltext.]
- Duangkamol, Chuthamat,Pattarawarapan, Mookda,Phakhodee, Wong
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p. 1945 - 1949
(2016/10/21)
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- Ultrasound-assisted synthesis of substituted guanidines from thioureas
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Ultrasound-assisted synthesis of guanidine derivatives was developed using 2,4,6-trichloro-1,3,5-triazine as an inexpensive dehydrosulfurization reagent. Both 1,3-alkylaryl- and 1,3-diaryl-thioureas were rapidly converted into carbodiimides before subsequent reaction with aromatic or aliphatic amines. The method allows rapid access to highly substituted guanidines in good to excellent yields under mild conditions and with minimal use of solvent.
- Pattarawarapan, Mookda,Jaita, Subin,Wangngae, Sirilak,Phakhodee, Wong
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supporting information
p. 1354 - 1358
(2018/03/29)
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- A method of manufacturing a carbodiimide compound
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PROBLEM TO BE SOLVED: To provide a novel method that can efficiently produce a carbodiimide compound without using substances that are harmful, hazardous, expensive, or difficult to obtain.SOLUTION: The method of producing a carbodiimide compound includes converting a thiourea compound having a specific structure to a carbodiimide compound having a specific structure in the presence of at least one of an iron compound and a molybdenum compound.
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Paragraph 0056-0059; 0062; 0063
(2018/03/02)
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- Naphthyridine derivatives as a model system for potential lithium-sulfur energy-storage applications
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Naphthyridines have been identified as structural elements in sulfurized polyacrylonitrile, which is a common electrode material in lithium-sulfur batteries. Some dibenzonaphthyridine derivatives with a fused dithiolo moiety were prepared as model compounds for battery studies. These heterocyclic systems were prepared via the corresponding diphenyldicarbamide intermediate. Followed by naphthyridione formation, stepwise installation of the dithiolane subunit occurred in a straightforward manner. In the solid state, the heteroaromatic system is completely planar and was thoroughly characterized. Initial battery cycling tests indicated a potential use of such structural motifs in sulfur-lithium systems.
- Resch, Sebastian,Schneider, Anna-Rebekka,Beichler, Ronja,Spera, Marcelle B. M.,Fanous, Jean,Schollmeyer, Dieter,Waldvogel, Siegfried R.
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supporting information
p. 933 - 937
(2015/02/19)
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- Synthesis of phosphaguanidines by hydrophosphination of carbodiimides with phosphine boranes
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The direct addition of anionic secondary phosphine boranes to carbodiimides yields both chiral and achiral phosphaguanidine boranes under ambient temperature conditions. An analogous preparation of menthol-derived phosphinite boranes is also described. These products can be deborinated to give the corresponding phosphines, and subsequently oxidized to give phosphine oxides. The robustness of this method was further demonstrated in the synthesis of structurally novel cyclic phosphaguanidines. (Chemical Equation Presented).
- Busacca, Carl A.,Milligan, John A.,Rattanangkool, Eakkaphon,Ramavarapu, Cyrus,Chen, Anji,Saha, Anjan K.,Li, Zhibin,Lee, Heewon,Geib, Steven J.,Wang, Guijun,Senanayake, Chris H.,Wipf, Peter
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p. 9878 - 9887
(2015/01/09)
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- Sydnone photochemistry: Direct observation of earl's bicyclic lactone valence isomers (oxadiazabicyclo[2.1.0] pentanones), formation of carbodiimides, reaction mechanism, and photochromism
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The matrix photolyses of 3-phenyl-, 3-pyridyl, and 3,4-diphenylsydnones 16, 19, and 22 were investigated by matrixisolation infrared spectroscopy. The formation of the neutral, bicyclic lactone valence isomers postulated by Earl - the oxadiazabicyclo[2.1.0]pentanones exo-17 and exo-20 - was clearly observed in the first two cases and is also likely in the case of exo-23 (C=Oabsorptions in the IR at 1881, 1886, and 1874 cm -1, respectively). The efficient photodecomposition of sydnones to carbodiimides RN=C=NR0 (18, 21, and 24) and CO2 was established in all three cases. The formation of benzonitrile 27 and azacycloheptatetraene 29 in the matrix photolysis of diphenylsydnone 22 is indicative of diphenylnitrile imine PhCNNPh 26 as an intermediate (2340 cm -11). Neither bicyclic lactones nor carbodiimides have been observed previously in sydnone photochemistry. A general reaction mechanism for the formation of carbodiimides, nitrile imines, and photochromism is put forward. CSIRO 2014.
- Veedu, Rakesh N.,Kvaskoff, David,Wentrup, Curt
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p. 457 - 468
(2014/04/03)
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- Dehydrogenative desulfurization of thiourea derivatives to give carbodiimides, using hydrosilane and an iron complex
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Dehydrogenative desulfurization of thiourea derivatives (RNHC(S)NHR′) has been achieved, to give carbodiimides (RNCNR′), in the reaction with hydrosilane and (η5-C5H5)Fe(CO) 2Me. The obtained carbodiimide reacted with (η5-C 5H5)Fe(CO)(SiR3) formed in the reaction to give an N-silylated η2-amidino iron complex, which was isolated and then characterized by X-ray analysis.
- Hayasaka, Kazumasa,Fukumoto, Kozo,Nakazawa, Hiroshi
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p. 10271 - 10276
(2013/07/26)
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- "On water": Efficient iron-catalyzed cycloaddition of aziridines with heterocumulenes
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In suspension: The reaction of aziridines with heterocumulenes in the presence of Fe(NO3)3×9 H2O in aqueous suspension provides access to functionalized five-membered heterocycles in good to high yields. This protocol has a wide substrate scope, is simple, and uses a nontoxic and cheap catalyst. Copyright
- Sengoden, Mani,Punniyamurthy, Tharmalingam
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supporting information
p. 572 - 575
(2013/02/23)
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- Oxo/Imido heterometathesis reactions catalyzed by a silica-supported tantalum imido complex
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Grafting Ta(=NtBu)(CH2CMe2Ph)3 onto the surface of silica partially dehydroxylated at 300°C leads to the formation of the surface imido complex (≡SiO)2Ta(=N tBu)(CH2CMe2Ph) as a major species, which was characterized with EXAFS, 13C CP/MAS NMR, diffuse reflectance FTIR, elemental analyses, and chemical reactivity. The obtained material acts as an efficient heterogeneous catalyst for various oxo/imido heterometathesis transformations: imidation of ketones and DMF with N-sulfinylamines and condensation of N-sulfinylamines into sulfurdiimines and phenyl isocyanate into diphenylcarbodiimide.
- Zhizhko, Pavel A.,Zhizhin, Anton A.,Belyakova, Olga A.,Zubavichus, Yan V.,Kolyagin, Yuriy G.,Zarubin, Dmitry N.,Ustynyuk, Nikolai A.
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p. 3611 - 3617
(2013/07/26)
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- Molecular structure and acid/base properties of 1,2-dihydro-1,3,5-triazine derivatives
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It is shown that guanidine and its N,N-dimethyl-derivative react with substituted carbodiimides, affording hitherto unknown 1,2-dihydro-1,2,3-triazine derivatives. The structures of three novel compounds of this type and their perchlorate salts were elucidated by spectroscopic (IR, 1H and 13C NMR and 15N solid-state NMR) and X-ray diffraction methods. The acid/base properties were also determined experimentally and by using DFT calculations with the B3LYP functional. The most basic compound was found to be dihydrotriazine 3, the basicity of which with the pKa value of 23.3 is of the same order of magnitude as that of tetramethylguanidine. Acidity measurements revealed that all the compounds studied are very weak acids with pKa values in the range of 25.8-30.8 pKa units in acetonitrile. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Trukil, Vjekoslav,Ilovic, Ivica,Matkovic-Alogovic, Dubravka,Saame, Jaan,Leito, Ivo,Ket, Primo,Plavec, Janez,Eckert-Maksic, Mirjana
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experimental part
p. 86 - 96
(2012/02/06)
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- Computational tools for mechanistic discrimination in the reductive and metathesis coupling reactions mediated by titanium(IV) isopropoxide
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A theoretical study has been carried out at the B3LYP/LANL2DZ level to compare the reactivity of phenyl isocyanate and phenyl isothiocyanate towards titanium(IV) alkoxides. Isocyanates are shown to favour both mono insertion and double insertion reactions. Double insertion in a head-to-tail fashion is shown to be more exothermic than double insertion in a head-to-head fashion. The head-to-head double insertion leads to the metathesis product, a carbodiimide, after the extrusion of carbon dioxide. In the case of phenyl isothiocyanate, calculations favour the formation of only mono insertion products. Formation of a double insertion product is highly unfavourable. Further, these studies indicate that the reverse reaction involving the metathesis of N,N ′-diphenyl carbodiimide with carbon dioxide is likely to proceed more efficiently than the metathesis reaction with carbon disulphide. This is in excellent agreement with experimental results as metathesis with carbon disulphide fails to occur. In a second study, multilayer MM/QM calculations are carried out on intermediates generated from reduction of titanium(IV) alkoxides to investigate the effect of alkoxy bridging on the reactivity of multinuclear Ti species. Bimolecular coupling of imines initiated by Ti(III) species leads to a mixture of diastereomers and not diastereoselective coupling of the imine. However if the reaction is carried out by a trimeric biradical species, diastereoselective coupling of the imine is predicted. The presence of alkoxy bridges greatly favours the formation of the d,l (±) isomer, whereas the intermediate without alkoxy bridges favours the more stable meso isomer. As a bridged trimeric species, stabilized by bridging alkoxy groups, correctly explains the diastereoselective reaction, it is the most likely intermediate in the reaction.
- Kumar, Akshai,Samuelson, Ashoka G
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p. 1343 - 1352
(2013/06/05)
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- Three-component sequential synthesis of N,N′-disubstituted 5-arylidenedihydropyrimidine-2,4-dione
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A three-component sequential process consisting in (1) in situ formation of carbodiimides by Staudinger reaction, (2) reaction with 2-(bromomethyl)-3-aryl- 2-propenoic acids, and (3) final cyclization of the resulting N-acylurea intermediates in order to obtain the synthesis of an array of N,N′-disubstituted 5-arylidenedihydropyrimidine-2,4-dione under mild conditions is presented.
- Bellucci, Maria Cristina,Volonterio, Alessandro
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supporting information; experimental part
p. 4733 - 4737
(2012/09/07)
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- Nitrile imines: Matrix isolation, IR spectra, structures, and rearrangement to carbodiimides
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The structures and reactivities of nitrile imines are subjects of continuing debate. Several nitrile imines were generated photochemically or thermally and investigated by IR spectroscopy in Ar matrices at cryogenic temperatures (Ph-CNN-H 6, Ph-CNN-CH317, Ph-CNN-SiMe323, Ph-CNN-Ph 29, Ph3C-CNN-CPh334, and the boryl-CNN-boryl derivative 39). The effect of substituents on the structures and IR absorptions of nitrile imines was investigated computationally at the B3LYP/6-31G level. IR spectra were analyzed in terms of calculated anharmonic vibrational spectra and were generally in very good agreement with the calculated spectra. Infrared spectra were found to reflect the structures of nitrile imines accurately. Nitrile imines with IR absorptions above 2200 cm -1 have essentially propargylic structures, possessing a CN triple bond (typically PhCNNSiMe323, PhCNNPh 29, and boryl-CNN-boryl 39). Nitrile imines with IR absorptions below ca. 2200 cm-1 are more likely to be allenic (e.g., HCNNH 1, PhCNNH 6, HCNNPh 43, PhCNNCH317, and Ph3C-CNN-CPh334). All nitrile imines isomerize to the corresponding carbodiimides both thermally and photochemically. Monosubstituted carbodiimides isomerize thermally to the corresponding cyanamides (e.g., Ph-N=C=N-H 5 Ph-NH-CN 8), which are therefore the thermal end products for nitrile imines of the types RCNNH and HCNNR. This tautomerization is reversible under flash vacuum thermolysis conditions.
- Begue, Didier,Qiao, Greg Guanghua,Wentrup, Curt
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supporting information; scheme or table
p. 5339 - 5350
(2012/05/20)
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- A New synthetic protocol for the preparation of carbodiimides using a hypervalent iodine(III) reagent
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A new, simple, and efficient preparation of symmetrical and unsymmetrical carbodiimides from the corresponding thioureas via dehydrosulfurization using a hypervalent iodine(III) reagent is described. The oxidation afforded carbodiimides in excellent yields and high selectivity. A possible mechanism for the transformation is proposed. Georg Thieme Verlag Stuttgart New York.
- Zhu, Chenjie,Xu, Dan,Wei, Yunyang
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supporting information; experimental part
p. 711 - 714
(2011/04/24)
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- Well-defined polyamide synthesis from diisocyanates and diacids involving hindered carbodiimide intermediates
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We have uncovered a novel polycondensation strategy for the synthesis of well-defined polyamides of narrow molecular weight distributions based on modifications of our sequential self-repetitive reaction ("SSRR") previously developed for diisocyanate-dicarboxylic acid polymerization. In our newly discovered SSRR polyamide formation mechanism, a small amount of hindered carbodiimide, N,N′-bis(2,6-diisopropylphenyl)carbodiimide (iPr-CDI) or a hindered isocyanate such as 2,6-diisopropylphenyl isocyanate (iPr-NCO), was introduced to the polymerization as an initiator, followed by simultaneous addition of diisocyanates and diacids monomers. By using this new reaction mode, the SSRR mechanism produces polyamide products of narrow molecular weight distributions with their dispersities reduced to 1.2-1.4, which is far lower than a range of >2.5 found in regular SSRR reactions. Significantly different from a conventional step-growth or standard SSRR reaction, the formation of a polymer backbone is preferential when the diacid is added to the requisite iPr-CDI in the first step, followed by a rearrangement to form amide and fragmented components for SSRR. The control of molecular weight is mainly attributed to the acid addition favoring the unhindered poly-CDI intermediates in the middle of the growing chains over the hindered-CDI at the chain terminals. It appears that the formation of a "hindered isocyanate" and the subsequent formation of a "new hindered-CDI" at the terminal end of growing amide-chains in each SSRR cycle force the acid again toward the preferred unhindered CDI sites dictating the observed outcome. This simple polyamide synthesis methodology is unique and unconventional, and it could significantly facilitate the development of tailored-made polyamides from a variety of diisocyanates and diacids.
- Chen, An-Liu,Wei, Kuan-Liang,Jeng, Ru-Jong,Lin, Jiang-Jen,Dai, Shenghong A.
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experimental part
p. 46 - 59
(2012/01/13)
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- Synthesis and X-ray crystal structures of imido and ureato derivatives of titanium(iv) phthalocyanine and their application in the catalytic formation of carbodiimides by metathesis from isocyanates
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The imido titanium phthalocyanine complex [PcTi(NDip)] (Dip = 2,6-diisopropylphenyl) 2a was synthesized from [PcTiO] 1 and one eq. of DipNCO. Due to the steric demand of the Dip group, addition of another isocyanate molecule to the TiN functionality of 2a does not occur even at high molar ratios of DipNCO. However, 1 reacts with 2 eq. of arylisocyanates containing sterically less demanding aryl groups producing N,N′- diarylureatotitanium(iv)phthalocyanines [PcTi{κ2-(NR)C(O) (N′R)}] (R = p-tolyl (Tol) 3a or mesityl (Mes) 3b). The N,N′ coordination (III) of the ureato ligand in 3a and 3b was proven by a single set of resonances for the aryl groups in their 1H-NMR spectra. An N,O coordination (IV) can therefore be excluded. This is also confirmed by the X-ray crystal structure of 3a. Upon heating [PcTiO] and an excess of aryl isocyanates for 6 days, a steady evolution of CO2 was observed and a white precipitate, identified as the corresponding diarylcarbodiimides (V), could be isolated. Therefore this reaction was applied in the metathetic conversion of two isocyanate molecules into diarylcarbodiimides (V) and CO2. Additionally, imido titanium Pc's 2b (R = tBu) and 2c (R = Mes) were prepared by a more general synthetic strategy, reacting the potassium salt of the ligand PcK2 with appropriate imido titanium precursors.
- Darwish, Wael,Seikel, Elisabeth,Kaesmarker, Ralf,Harms, Klaus,Sundermeyer, Joerg
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experimental part
p. 1787 - 1794
(2011/05/07)
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- Manganese-catalyzed cleavage of a carbon-carbon single bond between carbonyl carbon and α-carbon atoms of ketones
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Singled out: Treatment of ketones with carbodiimides in the presence of a catalytic amount of either [{HMn(CO)4}3] or [Mn 2(CO)10] gave amides in good to excellent yields. In this reaction, the carbon-carbon single bond of a ketone is cleaved efficiently. The reaction also proceeded by using isocyanates instead of carbodiimides. Copyright
- Kuninobu, Yoichiro,Uesugi, Tadamasa,Kawata, Atsushi,Takai, Kazuhiko
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supporting information; experimental part
p. 10406 - 10408
(2011/12/04)
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- Metathesis of carbon dioxide and phenyl isocyanate catalysed by group(IV) metal alkoxides: An experimental and computational study
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The insertion reactions of zirconium(IV) n-butoxide and titanium(IV) n-butoxide with a heterocumulene like carbodiimide, carbon dioxide or phenyl isocyanate are compared. Both give an intermediate which carries out metathesis at elevated temperatures by inserting a second heterocumulene in a head-to-head fashion. The intermediate metallacycle extrudes a new heterocumulene, different from the two that have inserted leading to metathesis. As the reaction is reversible, catalytic metathesis is feasible. In stoichiometric reactions heterocumulene insertion, metathesis and metathesis cum insertion products are observed. However, catalytic amounts of the metal alkoxide primarily led to metathesis products. It is shown that zirconium alkoxides promote catalytic metathesis (isocyanates, carbon dioxide) more efficiently than the corresponding titanium alkoxide. The difference in the metathetic activity of these alkoxides has been explained by a computational study using model complexes Ti(OMe) 4 (1bTi) and Zr(OMe)4 (1bZr). The computation was carried out at the B3LYP/LANL2DZ level of theory. Indian Academy of Sciences.
- Kumar, Akshai,Samuelson, Ashoka G
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experimental part
p. 29 - 36
(2012/02/01)
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- O-Iodoxybenzoic acid mediated oxidative desulfurization of 1,3-disubstituted thioureas to carbodiimides
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An efficient and mild oxidative desulfurization procedure using o-iodoxybenzoic acid has been developed for the synthesis of carbodiimides starting from easily synthesizable 1,3-disubstituted thioureas.
- Chaudhari, Pramod S.,Dangate, Prasad S.,Akamanchi, Krishnacharya G.
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supporting information; experimental part
p. 3065 - 3067
(2011/02/25)
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- A greener synthetic protocol for the preparation of carbodiimide
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A new and facile preparation of symmetrical and unsymmetrical 1,3-diaryl and aryl-alkyl carbodiimides via a dehydrosulfurisation of their corresponding thioureas is described. Herein, the classical method of oxidative desulfurisation of thiourea to carbodiimide involving toxic heavy metal oxides (HgO) has been replaced with an easily available, cost-effective and environmentally benign reagent, iodine. Simple reaction conditions, easy purification of the products and high yields are important attributes of the present methodology and perhaps the best alternative from a green chemistry perspective. The only limitation to this method however, is in the preparation of 1,3-dialkyl substituted carbodiimide.
- Ali, Abdur Rezzak,Ghosh, Harisadhan,Patel, Bhisma K.
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experimental part
p. 1019 - 1021
(2010/04/02)
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- Copper(II) acetate/oxygen-mediated nucleophilic addition and intramolecular C-H activation/C-N or C-C bond formation: One-pot synthesis of benzimidazoles or quinazolines
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Diarylcarbodiimides or benzylphenylcarbodiimides are converted to 1,2-disubstituted benzimidazoles or 1,2-disustituted quinazolines via addition/intramolecular C-H bond activation/C-N or C-C bond forming reaction using copper(II) acetate/oxygen [Cu(OAc)2/O2] as the oxidant at 100°C in one-pot cascade procedure. Copyright
- He, Hua-Feng,Wang, Zhi-Jing,Bao, Weiliang
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supporting information; experimental part
p. 2905 - 2912
(2010/12/29)
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- Room temperature metathesis of aryl isocyanates and aromatic aldehydes catalyzed by group(IV) metal alkoxides: An experimental and computational study
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Aromatic aldehydes and aryl isocyanates do not react at room temperature. However, we have shown for the first time that in the presence of catalytic amounts of group(IV) n-butoxide, they undergo metathesis at room temperature to produce imines with the extrusion of carbon dioxide. The mechanism of action has been investigated by a study of stoichiometric reactions. The insertion of aryl isocyanates into the metal n-butoxide occurs very rapidly. Reaction of the insertion product with the aldehyde is responsible for the metathesis. Among the n-butoxides of group(IV) metals, Ti(OnBu)4 (8aTi) was found to be more efficient than Zr(OnBu)4 (8aZr) and Hf(OnBu)4 (8aHf) in carrying out metathesis. The surprisingly large difference in the metathetic activity of these alkoxides has been probed computationally using model complexes Ti(OMe)4 (8bTi), Zr(OMe)4 (8bZr) and Hf(OMe)4 (8bHf) at the B3LYP/LANL2DZ level of theory. These studies indicate that the insertion product formed by Zr and Hf are extremely stable compared to that formed by Ti. This makes subsequent reaction of Zr and Hf complexes unfavorable.
- Kumar, Akshai,Samuelson, Ashoka G.
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experimental part
p. 338 - 345
(2010/05/01)
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- 1,4,2-Diazaphospholidine-3,5-diones and related compounds: A lecture on unpredictability in catalysis
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1,4,2-diazaphospholidine-3,5-diones and related compounds and unpredictability in catalysis was studied. The five-membered ring species 4 6, which are all readily accessible by the McCormack reaction, optionally with subsequent hydrogenation, were selected for this study. The use of saturated species of type 4 (1-organyl-phospholanes) as catalysts led to a complete reverse in the selectivity of the reaction, in favor of the formation of the isocyanate trimers. Owing to the high activity of the corresponding P-oxides in carbodiimidization reactions, it can be assumed that the findings can be attributed to partial air oxidation of the trivalent phosphorus species applied. The symmetrical species 6, in total contrast to the other two members of the series, do not exhibit any catalytic activity with respect to isocyanates and instead react cleanly with two equivalents of isocyanate to effect the extrusion of 1,3-diene.
- Richter, Frank U.
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supporting information; experimental part
p. 5200 - 5202
(2009/12/24)
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- Catalytic conversion of isocyanates to carbodiimides by cyclopentadienyl manganese tricarbonyl and cyclopentadienyl iron dicarbonyl dimer
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Isocyanates are catalytically converted to the corresponding carbodiimides in the presence of low valent transition metal complexes. The best conversions and yields were accomplished using [(C5R5)Fe(CO)2]2 (R = H or Me) or MeCpMn(CO)3 as catalysts.
- Rahman, A.K. Fazlur,Nicholas, Kenneth M.
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p. 6002 - 6004
(2008/02/10)
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- New facile synthesis of 3,5-dihydro-6H-imidazo[1,2-b]-1,2,4-triazol-6-ones by an iminophosphorane-mediated annulation
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Iminophosphorane 1 reacted with an aromatic isocyanate to unexpectedly give a mixture of carbodiimides 2, 3 and 4 through both the normal and the abnormal aza-Wittig reactions. 3-Aminoimidazolone 10 was obtained from the reaction of hydrazine hydrate with carbodiimide 2. Reaction of 10 with triphenyphosphane, hexachloroethane and triethylamine produced iminophosphorane 11 in good yield. A tandem aza-Wittig reaction of iminophosphorane 11 with isocyanate or CS 2 generated 3,5-dihydro-6H-imidazo[1,2-b]-1,2,4-triazol-6-ones 13 or 15 in satisfactory yield. Carbodiimides 18, obtained from normal aza-Wittig reactions of vinyl iminophosphorane 17 with aromatic isocyanates, reacted with hydrazine to give 2-arylamino-3-amino-4H-imidazol-4-ones 20. One-pot reactions of 2-arylamino-3-amino-4H-imidazol-4-ones 20 with isocyanates (or acyl chlorides), triphenyphosphane, hexachloroethane and triethylamine produced 3,5-dihydro-6H-imidazo[1,2-b]-1,2,4-triazol-6-ones 22 (or 23) in good yields. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Yuan, Ju-Zhen,Fu, Bo-Qiao,Ding, Ming-Wu,Yang, Guang-Fu
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p. 4170 - 4176
(2007/10/03)
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- Synthetic studies toward aryl-(4-aryl-4H-[1,2,4]triazole-3-yl)-amine from 1,3-diarylthiourea as urea mimetics
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A thiophile-promoted synthesis of disubstituted 4H-[1,2,4]triazole-3-yl- amines as urea mimetics from the corresponding 1,3-disubstituted thioureas has been studied, and the scope and limitations of this reaction are presented. The reaction proceeds through the formation of a carbodiimide, followed by a sequential addition-dehydration with acyl hydrazides. 1,3-Branched dialkylthioureas result in the formation of the corresponding ureas. The electronic and steric effects of the substitution on the phenyl rings of the 1,3-diarylthioureas play an important role in the formation of the intermediary carbodiimde and the direction of the subsequent ring closure of the N-acyl hydrazide adduct.
- Natarajan, Amarnath,Guo, Yuhong,Arthanari, Haribabu,Wagner, Gerhard,Halperin, Jose A.,Chorev, Michael
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p. 6362 - 6368
(2007/10/03)
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- Catalytic metathesis of carbon dioxide with heterocumulenes mediated by titanium isopropoxide
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The insertion of an isopropoxide ligand of titanium isopropoxide into heterocumulenes gives a product that carries out metathesis at elevated temperatures by undergoing insertion of a second heterocumulene in a head to head fashion, followed by an extrusion reaction. The Royal Society of Chemistry 2005.
- Ghosh, Rajshekhar,Samuelson, Ashoka G.
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p. 2017 - 2019
(2007/10/03)
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- Non-CNS acting opiates bearing guanidino substituents
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A series of guanidino-substituted opiates based on morphine, diprenorphine, and buprenorphine have been synthesized. Guanidines with aryl and alkyl substituents as well as unsubstituted ones have been attached to the opiate nucleus with spacer units of varying length. The spacer groups have mainly been attached to the opiates via the opiate nitrogen atom. A few compounds involving attachment through opiate oxygen atoms have been prepared, but were found to be ineffective as analgesics. The activity of the compounds as analgesics has been evaluated using the phenylquinone (PQ) abdominal-constriction test and their ability to enter the CNS evaluated with the Straub tail response. The compounds most active in the PQ abdominal-constriction test and showing no Straub tail behaviour contained aryl-substituted guanidines.
- Subasinghe, Kamani R.,Jackson, W. Roy,Young, Jacqui F.,Papanastasiou, Maria,Jarrott, Bevyn
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p. 427 - 438
(2007/10/03)
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- Synthesis, structure, and reactivity of (triphenylarsoranylidene)-methylcyclohepta-2,4,6-trienone derivatives: Reactions with heterocumulenes and an activated acetylene
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Stable arsonium ylide derivatives 7a,b bearing cyclohepta-2,4,6-trienyl and electron-withdrawing CO2Et and CN groups, respectively, have been prepared for the first time through a reaction of 2-chlorocyclohepta-2,4,6-trienone with the corresponding arsonium methylide derivatives in the presence of ButOK. Compounds 7a,b are isolated as stable crystalline compounds, which do not undergo hydrolysis even in acidic conditions. The X-ray crystal analysis revealed that their As-O bond distances (2.31 A for 7a, 2.39 A for 7b) lie below the sum of the van der Waals radii (3.37 A), and thus, there is appreciable bonding interaction between the arsenic and the oxygen elements. With a view to constructing a series of cyclohepta-annulated heterocycles and in order to gain a better understanding of a series of arsonium ylides, 7a,b were allowed to react with heterocumulenes such as carbon disulfide, phenyl isothiocyanate, diphenylcarbodiimido, and phenyl isocyanate, in a Wittig type reaction followed by electrocyclization or a formal [8 + 2]-type cycloaddition eliminating triphenylarsine sulfide or oxide to give 2H-cyclohepta[b]furan-2-thione, its imine, 2-phenylimino-2H-cyclohepta[b]pyrrole, and 2H-cyclohepta[b]furan-2-one. On the other hand, the reactions of 7a,b with dimethyl acetylenedicarboxylate (DMAD) give azulene derivatives.
- Mitsumoto, Yuhki,Nitta, Makoto
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p. 2268 - 2274
(2007/10/03)
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- Convenient preparation of heteroazulenes by the reaction of 2-aminotropone with heterocumulenes in the presence of a base
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Reactions of 2-aminotropone with heterocumulenes, N,N'-diphenylcarbodiimide, phenyl isothiocyanate, phenyl isocyanate, and carbon disulfide, in the presence of t-BuOK afforded 1-phenylcycloheptaimidazole-2(1H)-phenylimine, 1-phenylcyclohepataimidazole-2(1H)-thione, 1-phenylcycloheptaimidazol-2(1H)-one along with 2H-cycloheptaoxazol-2-one, and 2H-cycloheptathiazol-2-one along with 2H-cycloheptaoxazole-2-thione in good to moderate yields, respectively.
- Mitsumoto, Yuhki,Nitta, Makoto
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p. 2131 - 2137
(2007/10/03)
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- 2-Chloro-1,3-dimethylimidazolinium chloride. 1. A powerful dehydrating equivalent to DCC
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2-Chloro-1,3-dimethylimidazolinium chloride (DMC) (3) can act as a powerful dehydrating agent, replacing DCC (1) under nearly neutral conditions. Its application to acylation and dehydration is described.
- Isobe, Toshio,Ishikawa, Tsutomu
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p. 6984 - 6988
(2007/10/03)
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- N.C.A [11C]CO2 as a safe substitute for phosgene in the carbonylation of primary amines
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An efficient one-pot synthesis of [11C]ureas and [11C]isocyanates via dehydration of intermediately formed carbamate salts is described as a general alternative to their formation via [11C]phosgene. After optimization of the reaction parameters, in-target produced n.c.a. [11C]CO2 can be used for labelling in a one pot reaction within a very short reaction time of 10 minutes resulting in good radiochemical yields. The developed method has been applied to the 11C-carbonylation of aniline, benzyl- and phenethylamine and 1,2-diaminobenzene yielding the appropriate n.c.a. [11C]ureas in about 65, 85, 25 and 70% radiochemical yield (RCY), respectively. The presented reaction sequence can be handled easily and safely and lends itself to simple automation.
- Schirbel,Holschbach,Coenen
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p. 537 - 551
(2007/10/03)
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- Oxidative rearrangement and cyclisation of N-substituted amidines using iodine(III) reagents and the influence of leaving group on mode of reaction
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The products of reaction of N-substituted amidines 5 with hypervalent iodine reagents such as (diacetoxyiodo)benzene (DAIB), bis(trifluoroacetoxy)iodobenzene (BFIB) and [methoxy(tosyloxy)-iodo]benzene (MTIB) are determined by the reagent, the amidine substituents and the reaction temperature. C-Alkyl-N-arylamidines 5a-d cyclise in high yield giving benzimidazoles 6 but C,N-dialkyl- and C,N-diaryl-amidines 5e-l rearrange to give products derived from an intermediate carbodiimide. Use of N2-phenylfuran-2-carboximidamide 5j leads to N-(2-furyl)acetamide 15 in good yield, illustrating a convenient route to stable derivatives of highly unstable 2-aminofuran. The rearrangement of C,N-diarylamidines on reaction with DAIB contrasts with the observed formation of benzimidazole when the same precursors are treated with lead tetraacetate (LTA). Evidence is presented to support the view that the mode of reaction is determined by the nature of the leaving group in an imide intermediate 19: very good leaving groups [e.g. PhI, N2, AgCl and PhSO2O- (aq.)] appear to favour rearrangement whereas poorer leaving groups [e.g. Cl-, Me2S, Me3N and PhSO2O- (non-aq.)] favour cyclo-α-elimination.
- Ramsden, Christopher A.,Rose, Helen L.
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p. 2319 - 2327
(2007/10/03)
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- A mild and efficient preparation of carbodiimides
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Mono and diaryl carbodiimides were prepared in high yield under mild conditions by treating a thiourea with methanesulfonyl chloride in the presence of triethylamine and DMAP.
- Fell,Coppola
-
-
- Synthesis and Reactivity of N-heterocumulenes
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A number of N-heterocumulenes bearing the (Me3Si)2CH (BSM) substituent adjacent to the terminal nitrogen atom of the heterocumulene function, namely BSM-N=C=O (2), BSM-N=C=S (3), BSM-N=C=NR (4: R = BSM; 5: R = C6H5), BSM-N=C=CR1R2 (9a: R1 = R2 = C6H5; 9b: R1 = H, R2 = SiMe3; 10: R1 = R2 = CH3; 12: R1 = H; R2 = CH3), and BSM-N=S=O (14), have been synthesized.The synthetic utility of the BSM-N-substituted heterocumulenes has been explored through the creation of a carbanion center at the α position relative to nitrogen.In particular, the following reactions have been studied: (i) the nucleophilic addition of MeLi to compounds 2 and 5, (ii) the MeLi-induced deprotonation of ketene imines 9a,b (this investigation includes the study of the regiochemical output of the addition of electrophiles (H2O, MeI, Me2CHI) to the resulting 1,3-dipoles; and (iii) the TBAF-induced desilylation of compounds 2 and 9a followed by reaction with benzaldehyde.
- Barbaro, Gaetano,Battaglia, Arturo,Giorgianni, Patrizia,Guerrini, Andrea,Seconi, Giancarlo
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p. 6032 - 6039
(2007/10/03)
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- Preparation of -, -, and -Bicyclic Guanidines from C,C'-Bis(iminophosphoranes)
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A one-pot synthesis of -, -, and -rigid bicyclic guanidines (6, 8, 19, 21, 23) based on a bis(iminophosphorane)-mediated annulation strategy is reported.The crystal and molecular structure of the parent -bicyclic guanidine 8 has been established by X-ray diffraction.The crystallographically independent molecule forms dimers through a centre of symmetry by N-H***N hydrogen bonds.The molecule, and therefore the dimer, is statistically disordered in a 65/35 ratio.A statistical study of N-H***N hydrogen bonds of this kind of dimers has been carried out by using the Cambridge Structural Database. - Key Words: Bis(iminophosphoranes) / Guanidines, bicyclic / Aza Wittig reaction
- Molina, Pedro,Obon, Rosario,Conesa, Carlota,Arques, Antonio,Desamparados Velasco, M. de los,et al.
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p. 1641 - 1652
(2007/10/02)
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- Selective and Efficient Syntheses of Perhydro-1,3,5-triazine-2,4,6-triones and Carbodiimides from Isocyanates Using ZP(MeNCH2CH2)3N Catalysts
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With concentrations as low as 0.0033 mol percent ZP(MeNCH2CH2)3N (Z = lone pair, 1) isocyanates are catalytically trimerized to perhydro-1,3,5-triazine-2,4,6-triones (isocyanurates) at room temperature.This reaction proceeds readily in the presence or absence of solvent, and the catalyst can be recycled at least six times without detectable degradation.Though not as potent a catalyst as 1, the molecule in which Z = NPh (3) also facilitates this reaction, and evidence is adduced that the catalytically active species is the adduct 3*ArNCO (6).In contrast, Ch=P(MeNCH2CH2)3N (Ch = O, 4; Ch = S, 5) selectively catalyze the transformation of isocyanates to carbodiimides and do so more efficiently than their acyclic analogues O=P(NMe2)3 and (MeO)2P(S)Ph, respectively.The crystal structure of 4 is reported for the first time, and details of the crystal structure of I reported earlier by us in preliminary form are presented.Both structures support the hypothesis that P-Nax transannulation plays a lead role in the catalytic activities of 1 and 3 - 5.
- Tang, Jiansheng,Mohan, Thyagarajan,Verkade, John G.
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p. 4931 - 4938
(2007/10/02)
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- SYNTHESIS AND REACTIONS OF TRIPHENYLARSINIMINES
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Triphenylarsinimines formed in situ from isocyanates and triphenylarsine oxide have been found to react smoothly with carbonyl compounds like aldehydes, quinones and aromatic ketones giving the corresponding Schiff's bases in high yields.In the case of aldehydes, quinones or activated ketones, e.g., α-diketones, only a catalytic amount of triphenylarsine oxide is necessary for the reaction to proceed to completion.Quinones react with particular ease.Thus the previously unknown 9,10-phenanthrenequinone N-phenylimine 12 (R = Ph, Scheme IV) can be prepared in high yield from 9,10-phenanthrenequinone and phenyl isocyanate under catalytic influence of triphenylarsine oxide.Orthoquinones like 9,10-phenanthrenequinone react with vinylic isocyanates, forming monoimines 13 which rearrange to 1,4-oxazines 14 (Scheme V).Diisocyanates react under the catalytic action of triphenylarsine oxide with dialdehydes under mild conditions, forming some interesting new polymers 25, 26 in high yields.Reactions with aliphatic isocyanates give N-alkyl-N'-arylcarbodiimides, whereas reactions with isothiocyanates proceed through intermediates 20 and 21 to mixed carbodiimides 16, 24 and 25. Key words: Triphenylarsinimines; synthesis; reactions; Schiff's bases; unsymmetrical carbodiimides; polymers.
- Froeyen, Paul
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-
- Carbodiimides as important intermediates in the reaction of isocyanates with carboxylic acids
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The reaction between isocyanates and carboxylic acids is known to lead to amides.We have studied the mechanism of catalysis of this reaction by phospholene oxides. The reaction between phenyl isocyanates and benzoic acid was monitored under various conditions using High-Pressure Liquid Chromatography.It was found that the catalyst reacts with the isocyanate under formation of a carbodiimide.The carbodiimide reacts with the carboxylic acid to form amide and isocyanate via an N-acylurea as intermediate.The catalyst is partly deactivated by the acid.The phospholene catalyst was only found effective in reactions with aromatic isocyanates.
- Schotman, A. H. M.,Mijs, W. J.
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-