606-03-1Relevant academic research and scientific papers
Method for preparing aromatic isocyanate terpolymer
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Paragraph 0020; 0026; 0030-0031; 0033-0039, (2021/06/22)
The invention discloses a method for preparing an aromatic isocyanate terpolymer in the field of high polymer material synthesis, which comprises the following steps of S1, respectively taking dimethylacetamide, ethanol and sodium hydride, taking dimethylacetamide as a solvent, taking ethanol and sodium hydride as catalysts, adding into a flask, and reacting at room temperature, S2, dropwise adding aromatic isocyanate as a reaction substrate, and carrying out a heating reaction under magnetic stirring, S3, after the mixture is cooled to the room temperature, pouring the mixture into ultrapure water to separate out a product, filtering the product, washing the precipitate with water and ethanol in sequence, and drying the precipitate in a drying oven to obtain a crude product. According to the method, dimethylacetamide is used as a solvent, under the condition that ethanol is not changed, a small amount of sodium hydride is used for base catalysis of polymerization of aromatic isocyanate such as 3, 5-dimethyl phenyl isocyanate to synthesize the compound aromatic isocyanate tripolymer, the yield of the aromatic isocyanate tripolymer can be increased, the cost can be reduced, and use by people is facilitated.
Dehydrogenative Synthesis of Carbamates from Formamides and Alcohols Using a Pincer-Supported Iron Catalyst
Bernskoetter, Wesley H.,Hazari, Nilay,Mercado, Brandon Q.,Townsend, Tanya M.
, p. 10614 - 10624 (2021/09/02)
We report that the pincer-ligated iron complex (iPrPNP)Fe(H)(CO) [1, iPrPNP- = N(CH2CH2PiPr2)2-] is an active catalyst for the dehydrogenative synthesis of N-alkyl- and N-aryl-substituted carbamates from formamides and alcohols. The reaction is compatible with industrially relevant N-alkyl formamides, as well as N-aryl formamides, and 1°, 2°, and benzylic alcohols. Mechanistic studies indicate that the first step in the reaction is the dehydrogenation of the formamide to a transient isocyanate by 1. The isocyanate then reacts with the alcohol to generate the carbamate. However, in a competing reaction, the isocyanate undergoes a reversible cycloaddition with 1 to generate an off-cycle species, which is the resting state in catalysis. Stoichiometric experiments indicate that high temperatures are required in catalysis to facilitate the release of the isocyanate from the cycloaddition product. We also identified several other off-cycle processes that occur in catalysis, such as the 1,2-addition of the formamide or alcohol substrate across the Fe-N bond of 1. It has already been demonstrated that the transient isocyanate generated from dehydrogenation of the formamide can be trapped with amines to form ureas and, in principle, the isocyanate could also be trapped with thiols to form thiocarbamates. Competition experiments indicate that trapping of the transient isocyanate with amines to produce ureas is faster than trapping with an alcohol to produce carbamates and thus ureas can be formed selectively in the presence of alcohols. In contrast, thiols bind irreversibly to the iron catalyst through 1,2 addition across the Fe-N bond of 1, and it is not possible to produce thiocarbamates. Overall, our mechanistic studies provide general guidelines for facilitating dehydrogenative coupling reactions using 1 and related catalysts.
Fast cyclotrimerization of a wide range of isocyanates to isocyanurates over acid/base conjugates under bulk conditions
Cheng, Ruihua,Liu, Wei,Wu, Li,Ye, Jinxing
, (2020/07/06)
An array of organic bases DMAP (4-dimethylaminopyridine), DBU (1, 8-diazabicyclo [5.4.0] undec-7-ene), TBD (1, 5, 7-triazabicyclo [4.4.0] dec-5-ene), and their base/acid conjugate organocatalyst systems were evaluated in the trimerization of various isocyanates. The performance depended greatly on the combination of the catalyst systems, and the [HTBD][OAc] (acetic acid) catalyst systems were considerably the most active in contrast to the corresponding DMAP and DBU counterparts. The [HTBD][OAc] catalyst system was capable of providing isocyanurates from the cyclotrimerization of various isocyanate substrates in excellent yields in seconds even under bulk conditions. A bifunctional catalytic mechanism over [HTBD][OAc] was proposed.
Highly efficient cyclotrimerization of isocyanates using N-heterocyclic olefins under bulk conditions
Li, Chengkai,Zhao, Wuchao,He, Jianghua,Zhang, Yuetao
supporting information, p. 12563 - 12566 (2019/10/28)
With a catalyst loading as low as 0.005%, high to excellent yields of isocyanurates could be achieved from N-heterocyclic olefin mediated organocatalytic cyclotrimerization of a wide range of isocyanates under bulk conditions. Experimental details coupled with structural characterization of the key intermediates led to comprehensive mechanistic studies of cyclotrimerization.
Aluminium-catalysed isocyanate trimerization, enhanced by exploiting a dynamic coordination sphere
Bahili, Mohammed A.,Stokes, Emily C.,Amesbury, Robert C.,Ould, Darren M. C.,Christo, Bashar,Horne, Rhian J.,Kariuki, Benson M.,Stewart, Jack A.,Taylor, Rebekah L.,Williams, P. Andrew,Jones, Matthew D.,Harris, Kenneth D. M.,Ward, Benjamin D.
supporting information, p. 7679 - 7682 (2019/07/08)
Main-group metals are inherently labile, hindering their use in catalysis. We exploit this lability in the synthesis of isocyanurates. For the first time we report a highly active catalyst that trimerizes alkyl, allyl and aryl isocyanates, and di-isocyanates, with low catalyst loadings under mild conditions, using a hemi-labile aluminium-pyridyl-bis(iminophenolate) complex.
Reactivities of zero-valent group 10 complexes toward organic isocyanates: Synthesis of metallacycles containing dimeric isocyanate units, isocyanate cyclotrimerization, and computational chemistry
Han, Young-Sung,Jung, Kang-Yeoun,Kim, Yong-Joo,Baeck, Kyoung Koo,Lee, Gang Min,Lee, Soon W.
, p. 15614 - 15625 (2019/10/19)
The reactions of [Pd(olefin)(PR3)2] (PR3 = PMe3, PMe2Ph) with two equivalents of an aryl or alkyl isocyanate afford cis-[Pd{-N(R)C(O)N(R)C(O)-}(PR3)2] (R = 1-naphthyl, 4-phenoxyphenyl), which are five-membered palladacycles bearing dimeric isocyanate units, or cyclic tetramers as assemblies of four five-membered palladacycles, [Pd{C(O)N(R′)C(O)N(R′)}(PMe3)]4, (R′ = 3-methylbenzyl, 4-methylbenzyl or 4-methoxybenzyl), depending on the alkyl substituent on R-NCO. Interestingly, these reactions afford cyclic trimers as catalytic products when two equivalents or excess amounts of benzyl isocyanate are used. In contrast, reactions of [Pt(olefin)(PR3)2] with two equivalents of an alkyl or aryl isocyanate afford only the five-membered platinacycle, namely cis-[Pt{-N(R)C(O)N(R)C(O)-}(PMe3)2] (R = 3-methylbenzyl, 4-methylbenzyl, 4-fluorobenzyl, 4-methoxybenzyl, (S)-(+)-(1-naphthyl)ethyl, (R)-(-)-(1-naphthyl)ethyl, 4-phenoxyphenyl and 2,6-difluorophenyl). Aided by theoretical calculations, we propose mechanisms for the formation of the five-membered palladacycle or platinacycle, the cyclic tetramer, and the cyclotrimerization of the organic isocyanate. In addition, the ligand-exchange reactions between a five-membered platinacycle bearing a chiral substituent such as (S)-(+)-(1-naphthyl)ethyl or (R)-(-)-(1-naphthyl)ethyl) moieties and 1,2-bis(diethylphosphino)ethane (DEPE), a chelating phosphine, clearly afford the corresponding platinacycle bearing a DEPE ligand with retention of chirality. On the other hand, reactions of [Ni(COD)2] with various organic isocyanates in the presence of tertiary phosphines only afford the corresponding cyclic trimers. In contrast, similar reactions in the presence of N-heterocyclic carbenes (NHC) such as 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) or 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidine (SIPr) afford unexpected adducts between R-NCO and the NHC ligand.
Cyclotrimerisation of isocyanates catalysed by low-coordinate Mn(ii) and Fe(ii) m-terphenyl complexes
Sharpe, Helen R.,Geer, Ana M.,Williams, Huw E. L.,Blundell, Toby J.,Lewis, William,Blake, Alexander J.,Kays, Deborah L.
supporting information, p. 937 - 940 (2017/01/17)
Two- and three-coordinate m-terphenyl complexes of manganese and iron are efficient catalysts for the selective cyclotrimerisation of primary aliphatic isocyanates affording isocyanurates in short reaction times and under mild conditions.
Macrocyclic complexes containing a platinacycle or palladacycle composed of an isocyanate dimer unit: Reactivity towards isocyanides and cyclotrimerization of isocyanates
Choi, Jun-Hwan,Jung, Kang-Yeoun,Kim, Yong-Joo,Im, Hye Jin,Lee, Soon W.
, p. 283 - 292 (2016/07/06)
The reactions of [Pt(styrene)(PMe3)2] with 2 equiv. of alkyl or aryl isocyanate affored five-membered platinacycles, cis-[Pt{-N(R)C(O)N(R)C(O)-}(PMe3)2] (R = CH2C6H5, p-ClC6H4, p-OMeC6H4). These complexes are the first examples of platinacycles containing an isocyanate dimer unit. When the five-membered bis(phosphine) platinacycles or palladacycles were treated with 2 equiv. of elemental sulfur, 16-membered cyclic products as an assembly of four platinacycles or palladacycles, [M(PR3){-N(R)C(O)N(R)C(O)-}]4, were readily obtained. These cyclic tetramers were cleaved using tert-butyl isocyanide (CN-tbutyl, 4 equiv.), affording the corresponding monomeric complexes, [M(PR3)(CN-tbutyl){-N(R)C(O)N(R)C(O)-}] (M = Pt, Pd). An unusual cyclotrimerization of organic isocyanates catalyzed by zerovalent Pt complexes or five-membered platinacycles was observed. In addition, the direct cyclotrimerization of alkyl or aryl isocyanates using dialkyl Pt(II) or Pd(II) complexes was investigated. The cross cyclotrimerization of an aryl isocyanate and its derivative using a zerovalent Pd complex was also investigated.
Cyclic tetramers of a five-membered palladacycle based on a head-to-tail-linked isocyanate dimer and their reactivity in cyclotrimerization of isocyanates
Lee, Seon Gye,Choi, Keun-Young,Kim, Yong-Joo,Park, Sujin,Lee, Soon W.
, p. 6537 - 6545 (2015/04/14)
Reactions of [Pd(styrene)(PR3)2], generated from trans-[PdEt2(PR3)2] and styrene, with 2 equiv. of benzyl isocyanate in THF at room-temperature afforded unusual cyclic Pd-tetramers of five-membered rings consisting of organic isocyanate dimers and palladium, [Pd(PR3){-C(O)N(R)C(O)N(R)-}]4 (PR3 = PMe3, 1; PR3 = PMe2Ph, 2). Additionally, a cyclic trimer, (RNCO)3, 3 (R = benzyl) was produced as a catalytic product. Treatment of the cyclic tetramer (1) with 4 equiv. of chelated phosphine, such as (1,2-bis(diethylphosphino)ethane) (DEPE) or (1,2-bis(dimethylphosphino)ethane) (DMPE), readily caused conversion to a metallacyclic cis-form, [Pd{N(R)C(O)N(R)C(O)}(P ～ P)] (P ～ P = DEPE, 4; P ～ P = DMPE, 5) in quantitative yields. In contrast, reactions of Pd(0)-PR3 with 2 equiv. of Ar-NCO (Ar = Ph, p-tolyl, p-ClC6H4) afforded metallacyclic complexes having a dimeric isocyanato moiety, cis-[Pd{C(O)N(Ar)-C(O)N(Ar)}(PR3)2] (PR3 = PMe3 Ar = C6H5, 6; p-MeC6H4, 7; p-Cl-C6H4, 8; PR3 = PMe2Ph, Ar = p-Cl-C6H4, 9). Treatment of the palladacyclic complex (8) with an equimolar amount of chelated phosphine such as DEPE readily caused conversion to a palladacyclic cis-form, [Pd{N(Ar)C(O)N(Ar)C(O)}(DEPE)], 10 in quantitative yield. The catalytic cyclotrimerization of benzyl isocyanate to [Pd(styrene)(PMe3)2] was achieved by varying the molar ratio of R-NCO (R = benzyl). In addition, catalytic cyclotrimerization was performed from the five-membered palladacyclic complexes or the Pd(0)-PR3 complex with excess Ar-NCO. This journal is
Metal-Free: A novel and efficient aerobic oxidation of primary amines to oximes using N, N', N''-trihydroxyisocyanuric acid and acetaldoxime as catalysts in water
Yu, Jiatao,Lu, Ming
, p. 1873 - 1878 (2014/08/18)
A general, efficient, and metal-free method for aerobic oxidation of aromatic primary amines to the corresponding oximes catalyzed by N,N',N''-trihydroxyisocyanuric acid and acetaldoxime with water as solvent is described. This practical method can use air as economic and green oxidant, water as green solvent, and tolerates a wide range of substrates, which can afford the target oximes in moderate to good yields. Georg Thieme Verlag Stuttgart. New York.
