Synthesis and some reactions of bis(triphenylstannyl)carbodiimide, N′-(triphenylstannyl)-N′-tritylcarbodiimide,and (triphenylstannyl)cyanamide

Some methods for preparing bis(triphenylstannyl)carbodiimide (I), N-(triphenylstannyl)-N′-tritylcarbodiimide (II), and (triphenylstannyl)cyanamide are described. (I) was found to react with 1,3-disubstituted thioureas in refluxing acetonitrile or toluene to give bis(triphenyltin) sulfide and the corresponding N,N′-disubstituted-N″-cyanoguanidine. Some evidence for a diorganocarbodiimide intermediate in this reaction was found. The reaction of(I) with thiourea in refluxing acetonitrile was found to give bis(triphenyltin) sulfide,(triphenylstannyl)cyanamide and unchanged thiourea. The reaction of (I) with cyanamide gave (triphenylstannyl)cyanamide. (Triphenylstannyl)cyanamide was found to react with bis(triphenyltin) oxide in refluxing acetonitrile to give (I). (Triphenylstannyl)cyanamide was found to disproportionate in refluxing benzene to give (I) and dicyandiamide. (II) was found to be more hydrolytically stable than (I). The SnN bonds in both (I) and (II) were found to be readily cleaved by acetic acid. It was found that triphenyltin iodide and triphenyltin chloride can be conveniently prepared in good yield by the reaction of bis(triphenyltin) oxide with either calcium iodide or calcium chloride in refiuxing acetonitrile.     

Preparation of some N-substituted N-(triphenylstannyl)cyanamides

Nine N-substituted N-(triphenylstannyl)cyanamides were prepared by allowing bis(triphenylstannyl)carbodiimide to react separately with acid chlorides, trifluoroacetic anhydride, alkyl chlorocarbonates, and benzenesulfonyl chloride. The tin in these compounds was shown to have a coordination number greater than four be means of IR and Mössbauer spectroscopy.     

Cleavage of α-(phenylthio)alkylboranes with N-chlorosuccinimide. A convenient route to monothioacetals and acetals

α-(Phenylthio)alkylboranes, which are easily prepared by two different homologation processes, are deboronated by N-chlorosuccinimide in mildly basic methanol to form monothioacetals or, with excess reagent, dimethyl acetals. Both boronic esters and trialkylboranes react, the latter considerably faster. The reaction is specific for the sulfur-substituted alkylborane group, suggesting that initial chlorination occurs at sulfur. Under free radical conditions, α-(phenylthio)alkaneboronic esters are cleaved to α-(phenylthio)alkyl chlorides by either N-chlorosuccinimide or sulfuryl chloride. Pinacol phenylthio(triphenylstannyl)methaneboronate with sulfuryl chloride yielded (phenylthio)dichloromethane, without any evidence of selectivity between carbontin and carbonboron bond cleavage.     

Mechanism and linear free energy relationships in the kinetics of formation of bicyclo[3.3.1]nonane derivatives from 1,3,5‐trinitrobenzene,phenyl‐substituted 1‐benzyl‐1‐(ethoxycarbonyl)‐2‐propanones,and triethylamine

The kinetics and mechanism of cyclization of the anionic sigma complex obtained from the reaction of 1,3,5‐trinitrobenzene (TNB) and 1‐benzyl‐1‐(ethoxycarbonyl)‐2‐propanone (BEP) in the presence of triethylamine (NEt₃) have been studied in CH₃CN–CH₃OH (50% v/v). The order of the reaction has been found to be zero in TNB and BEP, unity in NEt₃, and negative and nonintegral in triethylammonium chloride. The rate has been observed to increase slightly with an increase in the concentration of the added salt (tetraethylammonium chloride). The rate constants for the formation of bicyclic adducts from phenyl‐substituted BEP and TNB in the presence of triethylamine have been correlated with σ values. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 467–473, 2011     

Structure and mechanism formation of polyelectrolyte complex obtained from PSS/PAH system: effect of molar mixing ratio, base–acid conditions, and ionic strength

Colloidal dispersions of polyelectrolyte complexes were prepared in aqueous solutions. We have used mixtures containing the strongly charged anionic polyelectrolyte sodium polystyrene sulfonate (PSS) and the weak cationic polyelectrolyte polyallylamine hydrochloride (PAH). Both polymers have the same molecular weight. The complexes were obtained by adding drop by drop a solution of the anionic polyelectrolyte to excess cationic polyelectrolyte. In these conditions, sodium polystyrene sulfonate and polyallylamine hydrochloride self-assembled in nanometer-range complexes; the self-assembly is driven by electrostatic interactions, as well as by entropy changes due to counterion release. The electrostatic interactions were controlled in several ways: by changing the C _PSS/C _PAH concentration ratio, by modifying the pH (and thus the protonation degree of polyallylamine hydrochloride), and by adding sodium chloride (screened interactions). Dynamic light scattering experiments demonstrated that the hydrodynamics radius of the polyelectrolyte complex increases, changing from soluble to insoluble complex formation, when some physicochemical parameters are increased: the concentration ratio between polyelectrolytes, the sodium chloride concentration, and pH. Zeta potential measurements, as a function of the C _PSS/C _PAH concentration ratio, as well as of pH and ionic strength, allow us to state that the resulting particles have a structure constituted by a neutral core surrounded by a positively charged shell. The polyelectrolyte complexes have globular shapes, as observed by electron microscopy.     

New high-yield,one-step synthesis of polyglycolide from haloacetic acids

In a new, one-step synthesis, polyglycolide was prepared by the reaction of bromo- or chloroacetic acid with triethylamine in a nitromethane solution. It was discolored, by iodoacetic acid possibly as a result of iodine formed by the decomposition of triethylammonium iodide. The structure of polyglycolide was characterized by hydrolysis, ¹H-NMR and IR spectra, and x-ray powder diffraction, which indicated partial crystallinity. A mechanism is proposed for the formation of polyglycolide. A lower limiting value of the number-average molecular weight of 10⁴ was determined by cryoscopy in 1,3-dinitrobenzene for polyglycolide prepared from bromoacetic acid; the measurement was inaccurate because of the low solubility of the polymer. No significant effect of solvent (acetone, ether, or chloroform) on yield or melting point was observed; a higher yield was obtained in nitromethane. The polymer obtained with tri-n-propylamine and bromoacetic acid had properties similar to that obtained with triethylamine. No polymer was obtained with N,N-dimethylaniline and bromoacetic acid or with triethylamine and bromoacetic acid in aqueous solution.     

Urea and thiourea complexes with trifluoromethanesulfonic acid and its derivatives

Urea and thiourea form complexes with trifluoromethanesulfonic acid, its monohydrate, and lithium salt CF₃SO₃Li. Urea complexes with trifluoromethanesulfonic acid are also formed as a result of hydrolysis in the reaction of N,N′-bis(trimethylsilyl)carbodiimide or cyanamide with trifluoromethanesulfonic acid in water.     

Synthesis of bis(arylcarbonylamino-1H-benzimidazol-5-yl) ethers

A procedure has been developed for the synthesis of bis(arylcarbonylamino-1H-benzimidazol-5-yl) ethers by reaction of the corresponding substituted benzoyl chloride with sodium cyanamide, followed by treatment of the resulting N-cyanobenzamide with 4-(3,4-diaminophenoxy)benzene-1,2-diamine in acid medium.     

Cyanamide: a convenient building block to synthesize 4-aryl-2-cyanoimino-3,4-dihydro-1H-pyrimidine systems via a multicomponent reaction

4-Aryl-2-cyanoimino-3,4-dihydro-1H-pyrimidine derivatives were prepared using a multicomponent reaction by reacting a mixture of arene or heteroarenecarbaldehyde, 1,3-dicarbonyl compounds, and cyanamide under acidic conditions. The novelty of this approach derives from its use of cyanamide as a building block in a four-component Biginelli-type reaction. Varying the reaction conditions led to the formation of either N-(2-imino-6-phenyl-1,3,5-oxadiazinan-4-ylidene) cyanamide or 3,4-dihydropyrimidin-2(1H)-one. The type of heterocycle skeleton synthesized depends on the nature of the acid catalyst as well as the reaction conditions employed.     

Silver(I) and mercury(II) complexes of meta- and para-xylyl linked bis(imidazol-2-ylidenes)

Mononuclear silver and mercury complexes bearing bis-N-heterocyclic carbene (NHC) ligands with linear coordination modes have been prepared and structurally characterised. The complexes form metallocyclic structures that display rigid solution behaviour. A larger metallocycle of the form [L₂Ag₂]²⁺ [where L = para-bis(N-methylimidazolylidene)xylylene] has been isolated from the reaction of para-xylylene-bis(N-methylimidazolium) chloride and Ag₂O. Reaction of silver- and mercury-NHC complexes with Pd(NCCH₃)₂Cl₂ affords palladium-NHC complexes via NHC-transfer reactions, the mercury case being only the second example of a NHC-transfer reaction using a mercury-NHC complex.     

1-(Aziridine) carbonyl chlorides and 1-(aziridine) carbonyl quaternary ammonium chlorides. Rearrangement to 2-(chloroalkyl) isocyanates

Aziridine reacted with phosgene in the presence of an acid acceptor or with 1,1′-carbonylbis(pyridinium) chloride to produce 1-(aziridine)carbonyl chloride (XII) or 1-(aziridine)carbonyl pyridinium chloride (XIII), respectively, as transient intermediates. Attempts to trap and observe (XII) and (XIII) at -10° were unsuccessful. These elusive materials underwent facile rearrangements to 2 - chloroethyl isocyanate under these conditions. Aziridine reacted with 1,1′-carbonylbis(triethylammonium)chloride (VII) at -20° to give 1-(aziridine) carbonyl triethylammonium chloride (X) as a transient intermediate which proceeded to 2-chloroethyl isocyanate. At -10° this reaction produced N,N-diethyl-1-aziridinecarboxamide. Aziridine reacted with a large excess of phosgene in the absence of an acid acceptor to give N-2-(chloroethyl) carbamoyl chloride (III), 1,1′-bis(2-chloroethyl) urea (IV) and 2-(β-chloroethylamino)-2-oxazoline hydrochloride (V). Possible mechanisms for these reactions are discussed.     

Copper(II) complexes containing chiral substituted 2-(4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5-one-2-yl)pyridine ligands: Synthesis, X-ray structural studies and asymmetric catalysis

New chiral N,N-bidentate ligands derived from substituted 2-(4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5-one-2-yl)pyridines have been prepared and characterised by means of ¹H, ¹³C NMR spectroscopy and optical rotation. Their Cu(II) complexes were characterized by means of elemental analysis, ¹H NMR spectroscopy and MS. By means of X-ray diffraction, molecular geometry of the complex of 2-(1-methyl-4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5-one-2-yl)pyridine with copper(II) chloride was determined. The complex exhibits heterochiral dimeric arrangement of two square pyramids with one terminal and one bridge-forming chlorine atoms and two nitrogen atoms in the bases of the pyramids. The tops of these pyramids are formed by the remaining chlorine atoms. The complexes prepared catalyse the Henry reaction with the overall yields of 41-97% and with the maximum enantioselective excess of 19%.     

Rapid fabrication and formation mechanism of cyclotriphosphazene-containing polymer nanofibers

Cyclotriphosphazene-containing polymer nanofibers with uniform diameters, high aspect ratios, and high specific surface area have been synthesized rapidly at high yields under ultrasonic irradiation via a self-directing template approach. During the polymerization, triethylamine (TEA) as an acid acceptor absorbed a byproduct hydrogen chloride (HCl) to afford triethylamine hydrochloride (TEACl), acting as structure-directing template and guiding the formation of nanofibrous structures. The mechanism was confirmed by means of SEM, TEM, FTIR, XRD, TG, and N₂ adsorption method. The molecular structure of as-synthesized polymer nanofibers was characterized by solid state NMR and elemental analysis.     

An Efficient One-Pot Synthesis of N-Methoxy-N-methylamides from Carboxylic Acids

Abstract

Several N-methoxy-N-methylamides were prepared by the reaction of the corresponding carboxylic acids with N,O-dimethylhydroxylamine hydrochloride at room temperature using trichloromethyl chloroformate in the presence of triethylamine in excellent yields.     

Synthesis and structure determination of a stable organometallic uranium(v) imine complex and its isolobal anionic U(IV)-ate complex

The reaction of one equivalent of Cp*₂UCl₂ with 2-(trimethylsilylimino)-1,3-di-tert-butylimidazoline in boiling toluene afforded a one electron oxidation of the uranium metal and the opening of the N-heterocyclic ring, resulting in the formation of an organometallic uranium(V) imine complex. This complex crystallized with one molecule of toluene in the unit cell, and its solid-state structure was determined by X-ray diffraction analysis. When the same reaction was performed in perdeuterated toluene, a myriad of organometallic complexes were obtained, however, when equimolar amounts of water were used in toluene, the same complex was obtained, and its solid state characterization shows two independent molecules in the unit cell with an additional water molecule. For comparison of the geometric parameters, the corresponding isolobal anionic uranium(IV) complex [Cp*₂UCl₃]^? was synthesized by the reaction of Cp*₂UCl₂ with 1,3-di-tert-butylimidazolium chloride, and the resulting U(IV)-ate complex was characterized by X-ray diffraction analysis.     

A concise synthesis of asymmetrical N,N′-disubstituted guanidines

We present a new and concise method for the preparation of asymmetrical N,N′-disubstituted guanidines starting from thiourea via the reaction of N-Boc-protected N′-alkyl/aryl substituted thioureas with an amine in the presence of mercury(II) chloride and triethylamine.     

Syntheses and X-ray structures of Cu(II) and Zn(II) complexes of N,N′-dibenzyl-(R,R)-1,2-diaminocyclohexane and application to nitroaldol reaction

Chiral Cu(II) and Zn(II) complexes with N,N′-dibenzyl-(R,R)-1,2-diaminocyclohexane ligands were synthesized and characterized. X-ray crystal structures of these complexes reveal that Cu complex has the distorted square-planar geometry and the Zn one has the nearly tetrahedral pattern. The coordination of metals to the chiral diamine ligand leads to a 5-membered metallaheterocycle of (S,S)-configuration of nitrogen atoms. Their asymmetric catalytic activities to nitroaldol reaction of benzaldehyde and nitromethane were examined. The difference of the geometry around metals leads to the opposite preferential configuration of alcohol products using these chiral complexes as asymmetric catalysts in the presence of triethylamine or diisopropylethylamine.     

Copper(II) complexes derived from substituted 2,2′-bis-(4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5-one) ligands: Synthesis,structure and catalytic activity

New chiral N,N-bidentate 2,2′-bis-(4-isopropyl-4-methyl-4,5-dihydro-1H-imidazol-5-one) ligands have been prepared and characterised by their ¹H and ¹³C NMR spectra and/or optical rotation. The ligands prepared were then tested for their ability to form complexes with copper(II) salts. It was found that the most stable complex is formed from the 2,2′-bis-(4-isopropyl-1,4-dimethyl-4,5-dihydro-1H-imidazol-5-one) ligand and copper(II) chloride. The structure of this complex was determined by means of quantum-chemical computations at the B3LYP or UB3LYP/6-31G(d,p) level. According to the computations, the geometry of the copper atom most resembles a tetrahedral arrangement, which was also confirmed by means of X-ray structural analysis. It was found that the structure of this copper(II) complex does not allow the copper atom to coordinate to additional ligands; therefore, it is catalytically inactive in the asymmetric Henry reaction.     

Bridge functionalized bis-N-heterocyclic carbene rhodium(I) complexes and their application in catalytic hydrosilylation

A series of chelating bridge functionalized bis-N-heterocyclic carbenes (NHC) complexes of rhodium (I) were prepared by reacting the corresponding imidazolium salts with [Rh(COD)Cl]₂ in an in-situ reaction. For the N-methyl substituted complex with a PF₆-anion an X-ray crystal structure was exemplary obtained. All complexes were spectroscopically characterized and tested for the hydrosilylation of acetophenone.     

Synthesis and fungicidal activity of bis(2-arylcarbonylamino-1<Emphasis Type="Italic">H</Emphasis>-benzimidazol-5-yl) sulfones

A procedure has been developed for the synthesis of bis(2-arylcarbonylamino-1H-benzimidazol-5-yl) sulfones by reaction of the corresponding substituted benzoyl chloride with sodium cyanamide and subsequent treatment of the N-cyanobenzamide thus formed with 3,3′,4,4′-tetraaminodiphenyl sulfone in acid medium. The products were tested for fungicidal activity.