Carbodiimides Research Articles

Gallium Hydride-Catalyzed Selective Hydroboration of Unsaturated Organic Substrates.

The first examples of tetrasubstituted conjugated bis-guanidinate (CBG) supported monomeric and thermally stable gallium dihalides [LGaX2], (X=Cl (Ga-Cl), I (Ga-I)) and dihydride (Ga-H) [LGaH2] (where L={(ArHN)(ArN)-C=N-C=(NAr)(NHAr)}; Ar=2,6-Et2-C6H3) compounds are reported. The reaction of in situ generated LLi with 1.0 equiv. GaX3 (X=Cl, I) afforded compounds Ga-Cl and Ga-I. The reaction between Ga-Cl and Li[HBEt3] in benzene yielded the dihydride compound Ga-H. All reported compounds (Ga-Cl, Ga-I, and Ga-H) were characterized by NMR, HRMS, and single-crystal X-ray diffraction studies. Ga-H was probed for the hydroboration of carbodiimides (CDI), isocyanates, and isothiocyanates with HBpin. Compound Ga-H was also found effective for the catalytic hydroboration of imines, nitriles, alkynes, esters, and formates, affording the corresponding products in quantitative yields. Stoichiometric reactions with a CDI were performed to establish the catalytic cycle.

2-Picolylamino(diphenylphosphinoselenoic)amide supported zinc complexes: Efficient catalyst for insertion of N–H bond into carbodiimides, isocyanates, and isothiocyanate

GRAPHICAL ABSTRACT

2-Picolylamino(diphenylphosphinoselenoic)amide supported zinc complexes: Efficient catalyst for insertion of N–H bond into carbodiimides, isocyanates, and isothiocyanate

We report here the hydroamination of heterocumulenes such as carbodiimides, isocyanates, and isothiocyanates by zinc complexes supported by the ligand 2-picolylamino-(diphenylphosphinoselenoic)amide [{(Ph2P-(˭Se)}2NCH2(C5H4N)] (1). A series of zinc complexes [κ2-{(Ph2P-(˭Se)}2NCH2(C5H4N)ZnX2] [(X˭Cl (2), Br (3a), I (4)] were prepared from ligand 1 and the corresponding zinc dihalide in a 1:1 molar ratio at 60°C in a chloroform solvent. The reaction of ligand 1 and ZnBr2 in methanol yielded another zinc complex [κ2-{(Ph2P-(˭Se)}2NCH2(C5H4N)ZnBr2(CH3OH)] (3b). The molecular structures of compounds 3a, 3b, and 4 were established through single-crystal X-ray diffraction analyses. The solid-state structures of all the complexes revealed a κ2- chelation through pyridine nitrogen and selenium atoms of ligand 1 to the zinc ion. Complex 2 proved to be a competent pre-catalyst for the addition of the amine N–H bond to carbodiimides, isocyanates, and isothiocyanates. The reaction scope was expanded to reactions of aliphatic and aromatic amines with phenylisocyanate and phenylisothiocyanate in toluene solvents, which proceeded rapidly at room temperature with 5 mol% catalyst loading to yield (up to 99%) the corresponding derivatives of urea and thio-urea. However, a temperature of 90°C was needed for the hydroamination of N,N′ dicyclohexylcarbodiimide. We also report the most plausible mechanism of the hydroamination reaction.

Base Promoted Annulation of Carbodiimides to Access of Quinazoline and Their Derivatives

Base Promoted Annulation of Carbodiimides to Access of Quinazoline and Their Derivatives

Magnesium-Catalyzed Hydroboration of Carbodiimides

Magnesium-Catalyzed Hydroboration of Carbodiimides

Iron(III)-Catalyzed Chain Growth Reactions of Polymeric Methylene Diphenyl Diisocyanate

The overall goal of the present study was to identify the high molecular weight species formed during the synthesis and processing of polymeric methylene diphenyl diisocyanate (PMDI) and determine the root cause of the viscosity buildup in these materials. Initial studies focused on the use of MALDI-TOF mass spectrometry to examine the PMDI mixture and MALDI-TOF/TOF CID fragmentation for elucidating the degradation mechanisms of the identified compounds. The low molecular mass portion of the MALDI spectrum was observed to contain the expected PMDI and small quantities of carbodiimides (CDIs). The high molecular mass portion of the spectrum primarily contained 1,3-diazetidine branched carbodiimide dimers, uretonimine branched CDIs, and imino-s-triazine along with low levels of guanidine branched CDIs. The results of this study indicate that the root cause of the observed CDI defects was extensive branch formation through unexpected side reactions catalyzed by iron(III). These reactions lead to a buildup of...

Reactivity ofortho-Substituted Aryl–Palladium Complexes towards Carbodiimides, Isothiocyanates, Nitriles, and Cyanamides

Complexes [Pd(C(6)H(3)XH-2-R'-5)Y(N;N)] (X=O, NH; Y=Br, I; R'=H, NO(2); N;N=N,N,N',N'-tetramethylethylenediamine (tmeda), 2,2'-bipyridine (bpy), 4,4'-di-tert-butyl-2,2'-bipyridine (dtbbpy)) react with RN=C=E (E=NR, S) or RC identical withN (R=alkyl, aryl, NR''(2)) and TlOTf (OTf=CF(3)SO(3)) to give, respectively, 1) products of the insertion of the C=E group into the C--Pd bond, protonation of the N atom, and coordination of X to Pd, [Pd{kappa(2)-X,E-(XC(6)H(3){EC(NHR)}-2-R'-4)}(N;N)]OTf or [Pd(kappa(2)-X,N-{ZC(6)H(3)(NH=CR)-2-R'-4})(N;N)]OTf, or products of the coordination of carbodiimides and OH addition, [Pd{kappa(2)-C,N-(C(6)H(4){OC(NR)}NHR-2)}(bpy)]OTf; or 2) products of the insertion of the C identical withN group to Pd and N-protonation, [Pd(kappa(2)-X,N-{XC(6)H(3)(NH=CR)-2-R'-4})(N;N)]OTf.

Quantification of carboxyl groups in carbodiimide cross‐linked collagen sponges

Glutaraldehyde (GA) fixation of bioprosthetic tissue is a well adapted technique, with commercial products on the market for almost 40 years. Amine groups present in tissue react with GA to form different types of cross-links. An estimation of the degree of cross-linking of the tissue can be obtained by measuring the concentration of residual amine groups, which is frequently carried out with the 2,4,6 trinitrobenzene sulphonic acid (TNBS) assay. Cross-linked tissue and collagen matrices are usually further characterized by determining their physical properties (such as the shrinkage temperature), biological properties (such as resistance to enzymatic degradation), and mechanical properties before in vivo evaluation takes place. In an effort to improve the properties of cross-linked tissue and collagen, alternative cross-linking methods have been developed. One of these methods is based on the use of water soluble carbodiimides (CDI). It is generally accepted that this cross-linking method leads only to the formation of amide linkages between tissue carboxyl and amine groups. Therefore, until recently the TNBS assay was also used to determine the degree of cross-linking of CDI cross-linked tissue and collagen. However, it cannot be excluded that after activation of carboxyl groups of tissue and collagen by CDI, these groups can react with other nucleophiles (like hydroxyl groups) present in the matrix. To obtain a better insight in the degree of cross-linking of CDI cross-linked matrices a reliable assay for quantification of residual carboxyl groups is required. Up to now such an assay was not available. In this study a new assay to determine residual carboxyl groups in CDI cross-linked collagen matrices is presented. Reconstituted dermal bovine collagen matrices (RDBC) were cross-linked with a water soluble CDI and N-hydroxysuccinimide (NHS) and residual carboxyl groups were labeled using 5-bromomethyl fluorescein. Subsequently, the fluorescent label was released by mild hydrolysis and quantified with capillary zone electrophoresis. A calibration curve relating the concentration of carboxyl groups with peak intensities was obtained using Sephadex standards with known concentrations of carboxyl groups. The concentration of carboxyl groups in unprocessed RDBC as determined with this new technique was equal to the concentration of carboxyl groups measured by amino acid analysis. On the basis of the concentration of residual carboxyl groups determined for CDI/NHS cross-linked RDBC and RDBC, in which the amine groups were blocked with propionaldehyde before CDI/NHS cross-linking, it was concluded that activated carboxyl groups can also react with other groups (such as hydroxyl groups) present in the matrix. This implies that the crosslink density of RDBC matrices after treatment with CDI/NHS is higher than expected on the basis of amide bond formation only, as determined by the TNBS assay.

Hydricity‐Promoted [1,5]‐H Shifts in Acetalic Ketenimines and Carbodiimides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Synthesis of Coumarin-3-O-acylisoureas by Different Carbodiimides

Synthesis of Coumarin-3-O-acylisoureas by Different Carbodiimides

Evaluation of carbodiimides using a competition method.

A competitive reaction of activated Boc-Ala-OH and Boc-Phe-OH with H-Leu-resin has been developed for assessing the relative efficiencies of different carbodiimides. This allowed a comparison of the efficiency of the carbodiimides N,N'-dicyclohexylcarbodiimide,N,N'-diisopropylcarbodiimide, N-tert-butyl-N'-methylcarbodiimide and N-tert-butyl-N'-ethylcarbodiimide. Comparable results were obtained when these reagents were used for the preformation of symmetrical anhydrides or of 1-hydroxybenzotriazole esters in situ. Differential incorporation was observed when asymmetrical carbodiimides were used for peptide bond formation by the direct carbodiimide procedure.

NEW APPLICATIONS OF IMINOPHOSPHORANES. THE PREPARATION OF β-KETO CARBODIIMIDESAND THEIR REARRANGEMENTTO 2-AMINO-1,3-OXAZOLES

Abstract β-Keto carbodiimides (3) have been synthesized by reacting 2-azido ketones (1) with triphenylphosphine in the presence of isocyanates/isothiocyanates; the former compounds (3) are readily transformed into 2-amino-1,3-oxazoles (4).

Chemie der isoblausäure: IV. additionen von CNH-komplexen des chroms, wolframs und eisens an heteroallen

“In situ” generated hydrogen isocyanide complexes are treated with cyclohexyl isocyanate and carbodiimides (PhNCNPh, CyNCNCy) to give metal-stabilized isocyano carboxamides ([M(CO) 5{CNC(O)NHCy}] (M = Cr, W), [Fe(Cp)(diphos) {CNC(O)NHCy}]BF 4) and isocayno carboxamidines ([Fe(CN)(Cp)(CO)-{CNC(-NPh)NHPh}], [Fe(Cp)(CO){CNC(NCy)NHCy} 2]BF 4, [Fe{CNC(NCy)NHCy} 2(ophen) 2](BF 4) 2), respectively.

Preparation of Carbodiimides from Phosphoramidates

La synthese se fait a partir de cyclohexyl isocyanate et O,O-diethyl N-(ω-dialkylamino-alkyl) phosphoramidate

2‐Azaallenium salts from the reaction of 1‐oxa‐3‐azabutatrienium salts with cyanamides and carbodiimides

1-Oxa-3-azabutatrienium salts 2 react with disubstituted cyanamides under [2 + 2 + 2] cycloaddition affording the 2-(alkylideneamino)-4,6-diamino-1,3,5-oxadiazinium salts 7a – o, which can be regarded as oxy-substituted 2-azaallenium salts. Addition of methanol leads to the oxadiazinium salts 8a, d, p. From 2n and dimethylcyanamide the 2-azaallenium salt 11 was obtained, which must be formed by an [1,5] isocyanatotropic rearrangement. Most butatrienium salts 2 react with two equivalents of carbodiimides R1 N C N CHR to form the 2-azaallenium salts 17a – k. The reaction mechanism includes an [1,5] hydride shift. Bulky substituted butatrienium salts 2 add three molecules of diisopropylcarbodiimide to give the 1,3,5-triazinium salts 20n, o. X-Ray structural analyses for 7a and 17a are reported. Darstellung von 2-Azaallenium-Salzen durch Reaktionen von 1-Oxa-3-azabutatrienium-Salzen mit Cyanamiden und Carbodiimiden Die 1-Oxa-3-azabutatrienium-Salze 2 reagieren mit disubstituierten Cyanamiden unter [2 + 2 + 2]-Cycloaddition zu den 2-(Alkylidenamino)-4,6-diamino-1,3,5-oxadiazinium-Salzen 7a – o, die man als oxysubstituierte 2-Azaallenium-Salze betrachten kann. Durch Anlagerung von Methanol entstehen die Oxadiazinium-Salze 8a, d, p. Aus 2n und Dimethylcyanamid erhalt man das 2-Azaallenium-Salze 11, dessen Bildung eine [1,5]-isocyanatotrope Umlagerung einschliest. Die Butatrienium-Salze 2 reagieren meist mit zwei Aquivalenten Carbodiimid vom Typ R1 N C N CHR zu den 2-Azaallenium-Salzen 17a – k, die durch eine [1,5]-Hydridverschiebung entstehen. Sterisch anspruchsvoll substituierte Butatrienium-Salze 2 lagern drei Molekule Diisopropylcarbodiimid and und ergeben die 1,3,5-Triazinium-Salze 20n, o. Es werden Rontgenstruktur-analysen der Verbindungen 7a und 17a angegeben.

Syntheses of a,b-Conjugated Carbodiimides and Ketenimines and Their Conversion to Some Heterocycles

Syntheses of a,b-Conjugated Carbodiimides and Ketenimines and Their Conversion to Some Heterocycles

Convenient and Improved Synthesis of Unstable Carbodiimides

Convenient and Improved Synthesis of Unstable Carbodiimides

Nucleophilic Substitution on Dialkoxy Disulfides. III. Reaction with Thioureas

Abstract 1,3- and 1,1-Disubstituted thioureas reacted with diethoxy disulfide to give carbodiimides and 1,2,4-thiadiazoles respectively. 1,1,3-Trisubstituted thioureas and diethoxy disulfide afforded trialkyl(trialkylamidino)thioureas.

Trifluoromethyl-aryl(alkyl)carbodiimides

Trifluoromethyl-aryl(alkyl)carbodiimides

A Facile and Improved Synthesis of Cyanoguanidines from Carbodiimides

A Facile and Improved Synthesis of Cyanoguanidines from Carbodiimides