Sequential photostimulated reactions of trimethylstannyl anions with aromatic compounds followed by palladium-catalyzed cross-coupling processes

The photostimulated reactions of several mono-, di-, and trichloroarenes and aryltrimethylammonium salts with Me(3)Sn(-) ions in liquid ammonia gave good yields of stannanes by the S(RN)1 mechanism. If the chloroarenes are not soluble in liquid ammonia, diglyme is another solvent to perform these reactions. The stannanes thus obtained can be arylated by further reaction with haloarenes through palladium-catalyzed reactions. If the palladium-catalyzed reaction is performed with a chloroiodoarene as substrate, the stannane reacts faster by the C-I bond via chemoselective cross-coupling reaction to give a chloroarene as product, which can be further arylated by a consecutive S(RN)1-Stille reaction or react with other substrates by another palladium-catalyzed reaction. These sequential reactions can also be performed with substrates with two leaving groups to give products in high yields.     

Heck reactions in monoglyme and diglyme using BmimCl as pre‐ligand

Heck reactions between iodobenzene and methyl acrylate were carried out in monoglyme and diglyme as solvents, using different ligands and palladium sources, and good to high yields were obtained in the production of (E)‐substituted olefins. The ionic liquid BmimCl was successfully utilized as pre‐ligand to substitute triphenylphosphine. Copyright © 2007 John Wiley & Sons, Ltd.     

Polarographic study of the effect of solvents on the reaction of Na amalgam with some vinyl monomers

Acrylonitrile, methacrylonitrile, ethyl acrylate, anthracene, and Na⁺ were studied polarographically in four solvent media: diglyme, DMSO, 25% H₂O in diglyme, and liquid NH₃. Cathodic shifts were observed for Na⁺ and anodic shifts for the vinyl monomers in DMSO, H₂O and NH₃. The values of ΔE = (E_{1/2, monomer} — E_{1/2, Na}⁺) were used in interpretation of the solvent effects observed previously for the reaction of these monomers with Na amalgam. In diglyme ΔE is very large (0.49 V for MeAN and 0.37 V) for AN, and therefore very slow reaction takes place. In DMSO, MeAN still reacts very slowly (ΔE = 0.23 V), while AN (ΔE = 0.09 V) reacts considerably faster than in diglyme and 100 times faster than MeAN in DMSO. Liquid ammonia brings both MeAN and AN to very low ΔE (0.08 V and ?0.05 V, respectively), and both reactions are very fast and yield only the hydrodimers. Water, on the other hand, has a large accelerating effect on the rate, but as it is a proton donor it yields only the reduced products.     

On the chichibabin amination of quinoline and some nitroquinolines

Quinoline is aminated into 2-aminoquinoline (55-60%) when treated with potassium amide/liquid ammonia/potassium permanganate at ?65°. When the amination is carried out by allowing the solution of quinoline in potassium amide/liquid ammonia to raise from ?60° to + 15° before addition of potassium permanganate, the main product is 4-aminoquinoline. Using as reagent liquid ammonia/potassium permanganate (thus without the presence of potassium amide) 3-nitroquinoline is exclusively aminated at ?40° into 4-amino-3-nitroquinoline. Using the same conditions, from 4-nitroquinoline 3-amino-4-nitroquinoline is obtained. The mechanism of these amination reactions is discussed.     

Synthesis of vinyl graft copolymers of poly(hexamethylene adipamide) and poly(m-phenylene isophthalamide)

Nylon 66 [poly(hexamethylene adipamide)] and Nomex [poly(m-phenylene isophthalamide)] were metalated by using solutions of sodium in liquid ammonia. Metalation of the Nomex polymer was also carried out by using sodium naphthalene in tetrahydrofuran. The metalated polymers were then reacted with acrylonitrile monomer to yield the corresponding anionic graft copolymers. The heterogeneous nature of these reactions is discussed in relation to the structure of the graft copolymers.     

Organic reactivity in liquid ammonia

Liquid ammonia is a useful solvent for many organic reactions including aliphatic and aromatic nucleophilic substitution and metal-ion catalysed reactions. The acidity of acids is modified in liquid ammonia giving rise to differences from conventional solvents. The ionisation constants of phenols and carbon acids are the product of those for ion-pair formation and dissociation to the free ions. There is a linear relationship between the pK(a) of phenols and carbon acids in liquid ammonia and those in water of slope 1.68 and 0.7, respectively. Aminium ions exist in their unprotonated free base form in liquid ammonia. The rates of solvolysis and aminolysis by neutral amines of substituted benzyl chlorides in liquid ammonia show little or no dependence upon ring substituents, in stark contrast with the hydrolysis rates of substituted benzyl halides in water which vary 10(7) fold. However, the rates of the reaction of phenoxide ions and amine anions with 4-substituted benzyl chlorides gives a Hammett ρ = 1.1 and 0.93, respectively. The second order rate constants for the substitution of benzyl chlorides by neutral and anionic amines show a single Br?nsted β(nuc) = 0.21 whereas those for substituted phenoxide ions generate a Br?nsted β(nuc) = 0.40. The rates of aromatic nucleophilic substitution reactions in liquid ammonia are much faster than those in protic solvents indicating that liquid ammonia behaves like a typical dipolar aprotic solvent in its solvent effects on organic reactions. Nitrofluorobenzenes (NFB) readily undergo solvolysis in liquid ammonia but oxygen nucleophiles, such as alkoxide and phenoxide ions, displace the fluorine of 4-NFB in liquid ammonia to give the corresponding substitution product with little or no competing solvolysis product. The Br?nsted β(nuc) for the reaction of 4-NFB with para-substituted phenoxides is 0.91, indicative that the decomposition of the Meisenheimer σ-intermediate is rate limiting. The aminolysis of 4-NFB occurs without general base catalysis by the amine and the second order rate constants generate a Br?nsted β(nuc) of 0.36, which is also interpreted in terms of rate limiting breakdown of the Meisenheimer σ-intermediate.     

Reactivity of free clusters

Recent studies of the reactions of free or isolated transition metal clusters with simple molecules will be reviewed. Cluster chemical reactions are carried out in a laser-vaporization cluster source coupled to a continuous-flow reactor. Reactions can be categorized as chemisorptive (or surface) reactions, and bulk reactions. Chemisorptive reactions can be characterized asfacile, in which most cluster sizes of a given metal are equally reactive towards a particular reagent, oractivated, in which strong dependence of reactivity on cluster size is found. Under the normal operating conditions of the cluster reactor, a reaction may be kinetically controlled or at equilibrium. Following chemisorption, adsorbate decomposition and product desorption may occur. Specific reactions to be discussed include the reactions of iron clusters with ammonia and with water and the reactions of nickel clusters with ammonia.     

The kinetics and mechanisms of aromatic nucleophilic substitution reactions in liquid ammonia

The rates of aromatic nucleophilic substitution reactions in liquid ammonia are much faster than those in protic solvents indicating that liquid ammonia behaves like a typical dipolar aprotic solvent in its solvent effects on organic reactions. Nitrofluorobenzenes (NFBs) readily undergo solvolysis in liquid ammonia and 2-nitrofluorobenzene is about 30 times more reactive than the 4-substituted isomer. Oxygen nucleophiles, such as alkoxide and phenoxide ions, readily displace fluorine of 4-NFB in liquid ammonia to give the corresponding substitution product with little or no competing solvolysis product. Using the pK(a) of the substituted phenols in liquid ammonia, the Br?nsted β(nuc) for the reaction of 4-NFB with para-substituted phenoxides is 0.91, indicative of the removal of most of the negative charge on the oxygen anion and complete bond formation in the transition state and therefore suggests that the decomposition of the Meisenheimer σ-intermediate is rate limiting. The aminolysis of 4-NFB occurs without general base catalysis by the amine and the second-order rate constants generate a Br?nsted β(nuc) of 0.36 using either the pK(a) of aminium ion in acetonitrile or in water, which is also interpreted in terms of rate limiting breakdown of the Meisenheimer σ-intermediate. Nitrobenzene and diazene are formed as unusual products from the reaction between sodium azide and 4-NFB, which may be due to the initially formed 4-nitroazidobenzene decomposing to give a nitrene intermediate, which may then give diazene or be trapped by ammonia to give the unstable hydrazine which then yields nitrobenzene.     

Solvent and salt effects on reaction of Na amalgam with acrylonitrile and methacrylonitrile

The reaction of acrylonitrile (AN) and methacrylonitrile (MeAN) with Na amalgam was studied in diglyme solution. It was shown that addition of dimethyl sulfoxide (DMSO) increases only the rate of hydrodimerization of AN to adiponitrile, while addition of water increases only the rate of hydrogenation of AN to propionitrile. The proposed mechanism assumes two separate intermediates for these two simultaneous reactions. The reaction of MeAN with Na amalgam was found to be 100 times slower than that of AN. DMSO increases the rate of both the hydrodimerization and hydrogenation reactions via the same intermediate. Addition of quaternary ammonium salts to AN in diglyme has an effect similar to that of DMSO. The salts, however, react at very low concentrations due to accumulation of the cations on the charged amalgam surface. The effect of the size and structure of the quaternary cations was studied and is discussed.     

Preparation of 1-ferrocenyl-2-methyl-1-propylamine,a highly effective chiral template in asymmetrically induced synthesis

The 1-ferrocenyl-2-methyl-1-propylamine (2a)is the most effective chiral template in asymmetrically induced peptide synthesis by stereoselective four component condensation (4CC). Two routes for the synthesis of this amine via its N,N-dimethyl derivative (12a) an described. One route involves the conversion of 12a into the corresponding azide 14a by treatment with methyl iodide/sodium azide in diglyme/water and subsequent reduction of the azide. The preferred other route consists of treating 12a with thioglycolic acid/formic acid to yield the carboxymethylmercapto derivative 9a and transformation of the latter into 2a with aqueous ammonia/ammonium chloride/mercuric chloride. Some related reactions are also discussed.     

Syntheses and Crystal Structures of Mononuclear and Binuclear Lanthanide Halide Complexes with Diglyme

Two types of isostructural complexes of lanthanide chlorides with diglyme have been synthesized. These are mononuclear molecular complexes [LnCl₃(diglyme)(THF)] (Ln = Eu ( 1 ), Gd ( 2 ), Dy ( 3 ), Er ( 4 ), Yb ( 5 ); diglyme = diethylen glycol dimethyl ether) and binuclear molecular complexes [LnCl₃(diglyme)]₂ (Ln = Dy ( 3d ), Er ( 4d ), Yb ( 5d )). Complex 1 was obtained by the reaction of [EuCl₃(DME)₂] with diglyme in THF. The complexes 2 – 5 and 3d – 5d resulted from reactions of LnCl₃·6H₂O, (CH₃)₃SiCl and diglyme in THF. The mononuclear complexes 2 – 5 crystallized directly from the solutions where the reactions of lanthanide compounds with diglyme took place. Recrystallizations of the powder products of the same reactions from dichloromethane resulted in the binuclear complexes 3d – 5d . Reactions of lanthanide bromide hydrates, (CH₃)₃SiBr and diglyme in THF achieved mononuclear molecular complexes [LnBr₃(diglyme)(L)] (Ln = Gd, L = H₂O ( 6 ); Ln = Ho, L = THF ( 7 )). Crystals of 6 and 7 were grown by recrystallization from dichloromethane. The lanthanide atoms (Ln = Eu–Yb) are seven‐coordinated in a distorted pentagonal bipyramidal fashion in all reported complexes, 1 – 7 and 3d – 5d . Four oxygen atoms and three halide ions are coordinated to lanthanide atoms in 1 – 7 , [LnX₃(diglyme)(L)]. Four chloride ions, two bridging and two nonbridging, and three oxygen atoms are coordinated to lanthanide atoms in 3d – 5d , [LnCl₃(diglyme)]₂.     

Substitution and elimination reactions of poly(epichlorohydrin) and poly(2-chloroethyl vinyl ether) using phase transfer catalysis

The reactions of poly(epichlorohydrin) (PECH) and poly(2-chloroethyl vinyl ether) (PCEVE) with various reagents were investigated using phase transfer catalyst (PTC) such as tetra-n-butylammonium bromide (TBAB), 18-crown-6 (CR6), and dicyclohexyl-18-crown-6 (DCHC) is a solid—liquid two-phase system. Although the reactions of these polymers hardly occurred without PTC in nonpolar solvents such as toluene and diglyme under mild conditions, the addition of PTC caused the reactions to proceed smoothly under the same conditions. In addition, the reactions of PECH and PCEVE with a strong base such as potassium hydroxide proceeded selectively through β-elimination reaction to produce the polymers with pendant vinyl groups. These results suggested this method is useful for the syntheses of functional polymers. On the other hand, it turned out that quaternary ammonium salts such as TBAB have higher catalytic activity than crown ethers such as CRG and DCHE in these reactions. Furthermore, the catalytic activity of quaternary ammonium salts was strongly influenced by their chain length and the structure of the polymers.     

Hydridosilazanes hydrolysis-condensation reactions studied by <Superscript>1</Superscript>H and <Superscript>29</Superscript>Si liquid NMR spectroscopy

Hydridosilazane compounds containing Si–N and Si–H bonds can be used as precursors of SiO_x materials. The hydrolysis-condensation reactions of tetramethyldisilazane, as a polyhydridosilazane model compound, were investigated by ¹H and ²⁹Si liquid NMR spectroscopy. These reactions were carried out at room temperature for up to 120 min in presence of water. The identified products are short linear siloxane species (hydride terminated polydimethylsiloxanes M^HD_xM^H) and cyclosiloxanes. Silicon hydride persistence in the reactional mixture suggested that silazane group is more sensitive to hydrolysis reaction than silicon hydride group. Moreover, additional experiments evidenced that the low steric hindrance of the silicon hydride influences the silazane hydrolysis kinetic. Hence the presence of ammonia released during silazane hydrolysis reaction was demonstrated to be a catalyst of the silicon hydride hydrolysis reaction.     

A Systematic Study of the Use of DL-Tartaric Acid in the Synthesis of Silica Materials Obtained by the Sol-Gel Method

DL-tartaric acid was used as a template for the formation of silica nanotubes and spheres by the sol-gel method from tetraethylorthosilicate (TEOS) as silica source. The reactions were carried out in ethanol/water mixtures in the presence of aqueous ammonia, between 0°C and 75°C, using both stirred and non-stirred conditions. TEM and SEM images show that the yield and microstructure of the silica is influenced by the synthetic conditions (temperature, ammonia (aq) concentration, gelation time, solvent mixture). It was observed that the chiral form of the tartaric acid used and the diffusion of TEOS to the template determines the eventual silica structure.     

Sampling small volumes of ambient ammonia using a miniaturized gas sampler

The development of a gas sampler for a miniaturized ambient ammonia detector is described. A micromachined channel system is realized in glass and silicon using powder blasting and anodic bonding. The analyte gas is directly mixed with purified water, dissolving the ammonia that will dissociate into ammonium ions. Carrier gas bubbles are subsequently removed from the liquid stream through a venting hole sealed with a microporous water repellent PTFE membrane. A flow restrictor is placed at the outlet of the sampler to create a small overpressure underneath the membrane, enabling the gas to leave through the membrane. Experiments with a gas flow of 1 ml min(-1), containing ammonia concentrations ranging from 9.4 ppm to 0.6 ppm in a nitrogen carrier flow have been carried out, at a water flow of 20 microl min(-1). The ammonium concentration in the sample solution is measured with an electrolyte conductivity detector. The measured values correspond with the concentration calculated from the initial ammonia concentration in the analyte gas, the fifty times concentration enhancement due to the gas-liquid volume difference and the theoretical dissociation equilibrium as a function of the resulting pH.     

Cyclization equilibrium constants and the conformations of polydimethylsiloxane chains

Experimental molar cyclization equilibrium constants for dimethylsiloxane cyclics having from 8 to ca 400 skeletal bonds are presented. The results for an undiluted equilibrate, an equilibrate in toluene solution, and an equilibrate in diglyme solution are compared. The increases in the equilibrium concentrations of cyclic oligomers, previously found to be large in good solvents (e.g., toluene) are found to be small in the poor solvent (diglyme). For macrocyclics, the cyclization equilibrium constants in the undiluted equilibrate and in diglyme (theta conditions) are found to be in good agreement with calculations which were carried out by assuming that chains are unperturbed and by using the rotational isomeric state model of Flory, Cresenzi, and Mark for polydimethylsiloxane. However, with chain polymer in dilute solution in a good solvent (toluene), the macrocyclization equilibrium constants are found to be lower than in the other two equilibrates. This result confirms the work of other authors who suggested that in this case the chains were expanded by excluded-volume effects.     

Influence of Boiling on the Radiolysis of Diglyme

The radiolysis of diethylene glycol dimethyl ether (diglyme) in a boiling state has been studied for the first time. Boiling facilitates the cleavage of internal C–O bonds, weakens the cage effect and diglyme regeneration processes, and facilitates the exchange and dimerization reactions of radicals. As compared with radiolysis at room temperature, the amount of unsaturated products of diglyme fragmentation formed during irradiation in the boiling state is smaller by a factor of 4, and the disproportionation products of heavy radicals are found in negligible amounts, if any. The yield of radiolytic decomposition of diglyme under boiling conditions is ～15 molecule/100 eV, which is higher than that at room temperature by a factor of almost 1.5.     

Functionalized arylzinc compounds in ethereal solvent: direct synthesis from aryl iodides and zinc powder and application to Pd-catalyzed reaction with allylic halides

Arylzinc compounds, ArZnX, were conveniently prepared in high yields by the reaction of zinc powder with aryl iodides, which contain electron-withdrawing groups such as CO(2)CH(3), CN, Br, or CF(3) at the ortho-, meta- or para-position, or electron-donating groups such as CH(3), OCH(3), or H, at 70 degrees C in THF, at 100 degrees C, or at 130 degrees C in diglyme, respectively. Pd(dba)(2) exhibited an outstanding efficient catalytic effect for the cross-coupling of these ethereal solutions of ArZnX with allylic halides to afford a variety of functionalized allylbenzenes in high yields; the reactions were mostly carried out at 0 degrees C for 5-30 min in the presence of 5 mol % of catalyst. The conversion of the aryl iodides to allylbenzenes via two reactions could be accomplished in one pot.     

Reactions of aliphatic fluoro-alcohols with CHClF2 at atmospheric pressure

The reactions of aliphatic fluoro-alcohols with chlorodifluoromethane (CHClF₂) at atmospheric pressure were examined. In the reaction of CF₃CF₂CH₂OH, the difluoromethylated ether was obtained in moderate yield by using ethers such as 1,4-dioxane, diglyme and THF, or their mixtures with water as a reaction solvent. While acetal and orthoformate were also produced, the selectivity of the difluoromethylated ether could be improved by adding water to the reaction. The effect of water could be explained by the reaction mechanism.     

REDUCTION OF NITROGEN FUNCTIONAL GROUPS WITH ELEMENTAL SULFUR IN LIQUID AMMONIA AND AMINES

Abstract

Nitrosobenzene and phenylhydroxylamine were reduced with elemental sulfur in liquid ammonia and amines to give aniline as the major product. Although hydrazobenzene was obtained by the reactions of azoxybenzene and azobenzene with elemental sulfur in liquid ammonia and amines, the expected aniline was not obtained. The utilities of elemental sulfur in liquid ammonia and amines as reductant is discussed.