Acyl iodides in organic synthesis. Reactions of acetyl iodide with urea,thiourea, and their <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-disubstituted derivatives

Acetyl iodide reacted with urea and its derivatives to give the corresponding N-substituted products. The reactions of acetyl iodide with thiourea, N,N′-dimethylthiourea, imidazolidine-2-thione, and hexahydropyrimidine-2-thione resulted in the formation of S- or N-acetyl derivatives, depending on the temperature and structure of the sulfur functionality (thione or thiol). By contrast, in the reaction of acetyl iodide with N,N′-bis(3-triethoxysilylpropyl)thiourea one ethoxy group on the silicon atom was replaced by iodine with formation of N-{3-[(diethoxy)iodosilyl]propyl}-N′-[3-(triethoxysilyl)propyl]thiourea. The latter decomposed on heating to give 3-triethoxysilylpropyl isothiocyanate and silicon-containing polymer with the composition C₄₅H₉₇IN₆O_14.5S₃Si₆.     

Preparation and protonation of 2-pyrimidyl- and 2-pyrazylpalladium(II) complexes

The oxidative addition of 2-chloropyrimidine or 2-chloropyrazine to [Pd(PPh₃)₄] yields a mixture of trans-[PdCl(C₄H₃N₂-C²)(PPh₃)₂] (I) and [PdCl(μ-C₄H₃N₂-C²,N¹)(PPh₃ (II) (C₄H₃N₂ = 2-pyrimidyl or 2-pyrazyl group). The mononuclear complexes I are quantitatively converted into the binuclear species II upon treatment with H₂O₂. The reaction of II with HCl gives the N-monoprotonated derivatives cis-[PdCl₂(C₄H₄N₂-C²)(PPh₃)] (III), from which the cationic complexes trans-[PdCl(C₄H₄N₂-C²)(L) (L = PPh₃, IV; PMe₂Ph, V; PEt₃, VI) can be prepared by ligand substitution reactions. Reversible proton dissociation occurs in solution for III–VI. The low-temperature ¹H NMR spectra of trans-[PdCl(C₄H₄N₂-C²)(PMe₂Ph)₂]ClO₄ show that the heterocyclic moiety undergoes restricted rotation around the PdC² bond and that the 2-pyrazyl group is protonated predominantly at the N¹ atom. These results and the ¹³C NMR data for the PEt₃ derivatives are interpreted on the basis of a significant d_π → π^★ back-bonding contribution to the palladium—carbon bond of the protonated ligands.     

Manganese cationic pyrazolylamidino complexes

The reactions of fac-[MnBr(CO)₃(NHC(CH₃)pz^∗-κ²N,N)] (pz^∗ = pz, dmpz; pzH = pyrazole; dmpzH = 3,5-dimethylpyrazole) with wet AgBF₄ in a 1:1 ratio lead to the cationic pyrazolylamidino complexes fac-[Mn(OH₂)(CO)₃(NHC(CH₃)pz^∗-κ²N,N)]BF₄. The aquo ligand is readily substituted by 2,6-xylylisocyanide (CNXyl) to give fac-[Mn(CNXyl)(CO)₃(NHC(CH₃)pz^∗-κ²N,N)]BF₄. The pyrazole complexes fac-[Mn(pz^∗H)(CO)₃(NHC(CH₃)pz^∗-κ²N,N)]BF₄ are obtained by treating fac-[MnBr(CO)₃(NCMe)₂] with AgBF₄ and then with pyrazole (pzH or dmpzH), in a 1:1:2 ratio. A similar reaction using 1:1:1 ratio and AgClO₄ leads to the acetonitrile complexes fac-[Mn(NCMe)(CO)₃(NHC(CH₃)pz^∗-κ²N,N)]ClO₄. The X-ray structures of the complexes show moderate hydrogen bonds interactions between the N-bond hydrogen of the pyrazolylamidino ligand and the anion. In the aquo complex, one of the hydrogens of the coordinated water molecule is also involved in a hydrogen bond.     

Polyfunctional Siloxane Water-Soluble Nanoparticles for Biomedical Applications

Hydrolysis of N-methyl-N-(2,3,4,5,6-pentahydroxyhexyl)-N′-(3-triethoxysilylpropyl)urea gave water-soluble polysiloxane nanoparticles. They can be used for the preparation of intensely luminescent stable aqueous suspensions of water-insoluble or poorly soluble compounds (Eu(BTFA)₃ · 6H₂O complex and tetracyano-tetraaryl-porphyrazines) for biomedical applications, in particular, for bioimaging.     

Structural isomerism of propionato copper(II) complex: crystal and molecular structure of tetrakis(μ-o-propionato)bis(methyl 3-pyridyl-N-carbamate)dicopper(II) at 190 K

The crystal and molecular structure of tetrakis(μ-o-propionato)bis(methyl 3-pyridyl-N-carbamate)dicopper(II) at 190 K was determined by X-ray analysis. The internuclear Cu⋯Cu distance is 2.6395(3) Å. CuO bond lengths are 1.961(1), 1.9678(9), 1.9828(9) and 1.9979(9) Å and CuN bond length is 2.165(1) Å. The non-bonding Cu(II)⋯Cu(II) contacts for nine binuclear Cu(II) propionates and hexacoordination of Cu(II) ion in the structure of [Cu(CH₃CH₂COO)₂(mpc)₂]0.25H₂O (mpc=methyl 3-pyridyl-N-carbamate) is consistent with the bond–valence sum model.     

Enantiomerically pure cyclopalladated diazaphospholidine

Enantiomerically pure (S)-2-(anilinomethyl)pyrrolidine (S)-2 was obtained from (S)-proline using a modified four-step procedure in a total yield of 56%. Diamine (S)-2 was converted to diazaphospholidine (S)-1 using ^oTolP(NMe₂)₂. The enantiomeric purity of ligand (S)-1 and diamine (S)-2 was determined by ³¹P and ¹H NMR spectroscopy, respectively, using a CN-palladacycle for their chiral derivatization. Direct cyclopalladation of (S)-1, using Pd(OAc)₂ in toluene under mild conditions regioselectively afforded the cyclopalladated complex with the (sp²)C–Pd bond. The aromatic C–H bond activation was confirmed by NMR spectral data and X-ray diffraction study of the PPh₃ derivative of the new P¹,C¹,N¹-chiral phosphapalladacycle.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-phenyltriflamide with 1,2-dibromoethane and propargyl bromide. Unexpected cleavage of С–С and С–N bonds

Reaction of N-phenyltriflamide with 1,2-dibromoethane under basic conditions in DMSO unexpectedly results in N-methyl-N-phenyltriflamide and 1,3-diphenylurea. The presumed reaction mechanism includes the formation of unstable intermediate disubstitution product TfN(Ph)CH₂CH2N(Ph)Tf that suffers the the С–С bond cleavage resulting in TfN(Me)Ph and N,N′-methanediylbis(N-phenyltriflamide). The latter reacts with K₂CO₃ releasing two molecules of potassium triflinate and after hydrolysis of diphenylcarbodiimide PhN=C=NPh gives 1,3-diphenylurea. With propargyl bromide, N-phenyltriflamide affords N-propargyl-Nphenyltriflamide in high yield. The bromination of the latter results in a mixture of Z,E-isomers of N-(2,3-dibromoprop-2-en-1-yl)-N-phenyltriflamide which undergo dehydrobromination giving first N-(3-bromopropanedienyl)-N-phenyltriflamide and then the products of the C–N bond cleavage: N-phenyltriflamide and 3,3-dimethoxyprop-1-yne.     

Intramolecular carbonyl?carbonyl interactions in W, Mo and Fe complexes containing the η-N-maleimidato ligand: X-ray, DFT and AIM studies

The crystal structures of (η⁵-C₅H₅)W(CO)₃(η¹-N-maleimidato) and (η⁵-C₅H₅)Fe(CO)₂(η¹-N-maleimidato) complexes were determined by single crystal X-ray diffraction. The molecular geometries of both structures are compared with those of the Mo analog of the W complex and ethyl-N-maleimide in order to find a relation between the geometrical features and the rate constants of the addition reaction of the sulfhydryl group of biomolecules to the ethylenic bond of the maleimidato fragment. For a deeper insight into the problem DFT calculation were performed. An analysis of atomic charges, using the CHELPG scheme, and of theoretical electron density function, using the AIM theory, was performed. In the (η⁵-C₅H₅)W(CO)₃(η¹-N-maleimidato), likewise in its Mo analog, the carbonyl?carbonyl interaction was found both for experimental and calculated structures. It is probably the first approach to explain this type of intramolecular interactions acting in organometallic compounds. This interaction can play the essential role in the reaction mechanism of nucleophilic addition to the maleimidato moiety. The AIM investigations indicate also the differences in the character of bonding between the η-N-maleimidato ligand and the central metal atom.     

Acid-catalysed hydrolysis of N-sulphonyl sulphilimines—II

The basicity and the acid-catalysed hydrolysis of ph(R)SNTs and o-HC₆H₄(Me)SNTs sulphilimines have been studied by UV spectrophotometric and kinetic methods, respectively, in aqueous HClO₄ (1–10 M) and 1:1 (v/v) EtOH/H₂O-HClO₄ (0.5–6 M). Depending on the constitution of the substrates, sulphilimine hydrolysis can follow three different courses, according to rate-acidity profiles, Bunnett-Olsen's treatment, activation parameters and product analysis. Most typical for sulphilimines is S_N2 hydrolysis with S^IV-N bond cleavage. In this case the reaction starts with the nucleophilic addition of water and is promoted by acid-base catalysis. If a relatively stable carbenium ion can be formed from R group, an S_N1 reaction with S^IVC bond cleavage takes place. Sulphilimine with X = o-CO₂H due to neighbouring-group participation hydrolyses very rapidly via acyloxy-sulphurane and acyloxy-sulphonium ion intermediates with five-memembered ring (S_Ni reaction involving S^IVN bond cleavage).     

Three-Component Reaction of 4-Methylpyridine with Alkyl Propiolates and Secondary Phosphine Chalcogenides

The reaction between 4-methylpyridine, alkyl propiolates, and secondary phosphine oxides proceeded as N-vinylation-C-phosphorylation with stereo- and regioselective formation of (E)-N-ethenyl-C²- phosphoryl-1,2-dihydropyridines [when using bis(2-phenylethyl)phosphine oxide] or (E)-N-ethenyl-C⁴- phosphoryl-1,4-dihydropyridines (when using diphenylphosphine oxide). The process occurred at 60–62°C within 3 h to give functional dihydropyridines in 40–82% yield. Under similar conditions, bis(2-phenylethyl) phosphine sulfide and selenide reacted with alkyl propiolates preferably by nucleophilic PH-monoaddition at the triple bond.     

Syntheses and structures of iron carbonyl complexes derived from N-(5-methyl-2-thienylmethylidene)-2-thiolethylamine and N-(6-methyl-2-pyridylmethylidene)-2-thiolethylamine

The reaction of N-(5-methyl-2-thienylmethylidene)-2-thiolethylamine (1) with Fe₂(CO)₉ in refluxing acetonitrile yielded di-(μ₃-thia)nonacarbonyltriiron (2), μ-[N-(5-methyl-2-thienylmethyl)-η¹:η¹(N);η¹:η¹(S)-2-thiolatoethylamido]hexacarbonyldiiron (3), and N-(5-methyl-2-thienylmethylidene)amine (4). If the reaction was carried out at 45 °C, di-μ-[N-(5-methyl-2-thienylmethylidene)-η¹(N);η¹(S)-2-thiolethylamino]-μ-carbonyl-tetracarbonyldiiron (5) and trace amount of 4 were obtained. Stirring 5 in refluxing acetonitrile led to the thermal decomposition of 5, and ligand 1 was recovered quantitatively. However, in the presence of excess amount of Fe₂(CO)₉ in refluxing acetonitrile, complex 5 was converted into 2-4. On the other hand, the reaction of N-(6-methyl-2-pyridylmethylidene)-2-thiolethylamine (6) with Fe₂(CO)₉ in refluxing acetonitrile produced 2, μ-[N-(6-methyl-2-pyridylmethyl)-η¹ (N_py);η¹:η¹(N); η¹:η¹(S)-2-thiolatoethylamido]pentacarbonyldiiron (7), and μ-[N-(6-methyl-2-pyridylmethylidene)-η²(C,N);η¹:η¹(S)-2- thiolethylamino]hexacarbonyldiiron (8). Reactions of both complex 7 and 8 with NOBF₄ gave μ-[(6-methyl-2-pyridylmethyl)-η¹(N_py);η¹:η¹(N);η¹:η¹(S)-2-thiolatoethylamido](acetonitrile)tricarbonylnitrosyldiiron (9). These reaction products were well characterized spectrally. The molecular structures of complexes 3, 7-9 have been determined by means of X-ray diffraction. Intramolecular 1,5-hydrogen shift from the thiol to the methine carbon was observed in complexes 3, 7, and 9.     

A re-examination of the decay kinetics of pulse radiolytically generated Br-2 radicals in aqueous solution

The decay of Br^-₂ in Ar-purged or N₂O-saturated aqueous solutions of KBr (0.01-1.0 M) in the pH range 1–7 has been re-examined using the techniques of pulse radiolysis and computer simulation. The dependence of the rate constant for the intrinsic decay of Br^-₂ on ionic strength (controlled by KBr) has been established; the values of k (Br^-₂ + Br^-₂) are (1.9 ± 0.1) × 10⁹, (2.2 ± 0.3) × 10⁹ and (2.4 ± 0.3) × 10⁹ M^-1 s^-1 in the presence of 0.01, 0.1 and 1.0 M KBr, respectively, independent of pH between 2 and 7. The computer simulation of the decay of Br^-₂ has also generated, for the latter species, ϵ = 10,000 ± 700 M^-1 cm^-1 at λ_max = 360 nm; this value has been calculated without making any assumption concerning G(Br^-₂). For the reduction of Br^-₂ by H atoms, a value of k (H + Br^-₂) = (1.4 ± 0.3) × 10¹⁰ M^-1 s^-1 has been obtained in the presence of 0.01-1.0 M KBr, independent of pH between 1–4. For the reduction of Br^-₂ by e^-_aq at pH 7 (10^-3 M phosphates) and μ = 0.1, a value of k (Br^-₂ + e^-_aq = (1.1 ± 0.2) × 10¹⁰ M^-1 s^-1 has been obtained.     

Kinetics of one-electron oxidation by the ClO radical

Pulse radiolysis studies were carried out to determine the rate constants for reactions of ClO radicals in aqueous solution. These radicals were produced by the reaction of OH with hypochlorite ions in N₂O saturated solutions. The rate constants for their reactions with several compounds were determined by following the build up of the product radical absorption and in several cases by competition kinetics. ClO was found to be a powerful oxidant which reacts very rapidly with phenoxide ions to form phenoxyl radicals and with dimethoxybenzenes to form the cation radicals (k = 7 × 10⁸ −2 × 10⁹ M^-1 s^-1). ClO also oxidizes ClO^-₂ and N^-₃ ions rapidly (9.4 × 10⁸ and 2.5 × 10⁸ M^-1 s^-1, respectively), but its reactions with formate and benzoate ions were too slow to measure. ClO does not oxidize carbonate but the CO^-₃ radical reacts with ClO^- slowly (k = 5.1 × 10⁵ M^-1 s^-1).     

Mixed N-heterocycles/N-heterocyclic carbene palladium(II) allyl complexes as precatalysts for direct arylation of azoles with aryl bromides

A series of mixed N-heterocycles/N-heterocyclic carbene palladium(II) allyl complexes with general formula [(NHC)Pd(η³-allyl)]₂(μ₂-N-heterocycles)(BF₄)₂ were prepared in one pot based on anion metathesis of (NHC)Pd(η³-allyl)Cl complexes and then ligand replacement with N-heterocycles [N-heterocycles?=?pyrazine (pyz), 4,4′-bipyridine (bpy) and trans-4,4′-bipyridylethylene (bpe)]. The solid-state structures shown dinuclear structures with two palladium(II) centers holding together by bridged N-heterocycles. Initially investigation of the obtained complexes as precatalysts for direct CH bond arylation of azoles with aryl bromides was carried out.     

fac-Cobalt(III)-azido complexes derived from substituted pyridyl-based tridentate amines

Four new mononuclear triazido-cobalt(III) complexes [Co(L ^1/2/4 )(N₃)₃] and [Co(L ³ )(N₃)₃]·CH₃CN where L ¹  = [(2-pyridyl)-2-ethyl]-(2-pyridylmethyl)-N-methylamine, L ²  = [(2-pyridyl)-2-ethyl]-[6-methyl-(2-pyridylmethyl)]-N-methylamine, L ³  = [(2-pyridyl)-2-ethyl]-[3,5-dimethyl-4-methoxy-(2-pyridylmethyl)]-N-methylamine, and L ⁴  = [(2-pyridyl)-2-ethyl]-[3,4-dimethoxy-(2-pyridylmethyl)]-N-methylamine, respectively, were synthesized and structurally characterized. The four complexes were characterized by elemental microanalyses, IR and UV–VIS spectroscopy and X-ray single crystal crystallography. The complexes display two strong IR bands over the frequency region 2,020–2,050 cm^?1 assigned for the asymmetric stretching frequency, ν_a(N₃) of the coordinated azides indicating facial geometry. The molecular structure determinations of the complexes were in complete agreement with fac-[Co(L)(N₃)₃] conformation in distorted octahedral Co(III) environment.     

The peculiar reaction of 2-arylazo-1-vinylpyrroles with trifluoroacetic acid: a novel synthesis of 2-methylquinolines

2-Arylazo-1-vinylpyrroles 1-6 react with CF₃CO₂H (benzene, reflux, 5 h) in a peculiar way: instead of expected electrophilic addition of CF₃CO₂H to the N-vinyl group, the latter is transferred to the azo group followed by NN bond cleavage to afford substituted 2-methylquinolines 10-12 in up to 56% yields. The reaction was shown (¹H, ¹³C, and ¹⁵N NMR) to start with the protonation of the azo group with further inter- and intramolecular involving of two protonated N-vinyl groups to finally build up the quinoline cycle over the aryl moiety.     

Nitrogen bridgehead compounds. Part 80 unusual reaction of ethyl 9-bromo-4-oxo-6,7,8,9-tetr ahydro-4h-pyrido[1,2-a]pyrimidine-3-carboxylates and N-Methylaniline

The acid-catalysed intramolecular nucleophilic addition of the phenyl ring to the C(9a) = N(1) double bond of ethyl 9-(N-methyl-N-phenyl)-4-oxotetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylates, formed in the reactions of ethyl 9-bromo-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylates and N-methylaniline, gave the first examples of a new tetracyclic pyrimido[1′,2′:1,2]pyrido[3,2-b]indole ring system ( 7 ). X-ray diffraction analysis of 7a revealed that the annelation of the pyrimidine and piperidine rings is transoid, while that of the piperidine and pyrroline rings is cis, the piperidine ring adopts an unusual ⁶T₈ twisted boat conformation, while the pyrroline ring has a ⁹T_8a conformation.     

Preparation and reactivity of half-sandwich hydrazine complexes of ruthenium and osmium

Hydrazine complexes [MCl(η⁶-p-cymene)(RNHNH₂)L]BPh₄ (1–6) [M = Ru, Os; R = H, Me, Ph; L = P(OEt)₃, PPh(OEt)₂, PPh₂OEt] were prepared by allowing dichloro complexes MCl₂(η⁶-p-cymene)L to react with hydrazines RNHNH₂ in the presence of NaBPh₄. Treatment of ruthenium complexes [RuCl(η⁶-p-cymene)(RNHNH₂)L]BPh₄ with Pb(OAc)₄ led to acetate complex [Ru(κ²–O₂CCH₃)(η⁶-p-cymene)L]BPh₄ (7). Instead, the reaction of osmium derivatives [OsCl(η⁶-p-cymene)(CH₃NHNH₂)L]BPh₄ with Pb(OAc)₄ afforded the methyldiazenido complex [Os(CH₃N₂)(η⁶-p-cymene)L}]BPh₄ (8). Treatment with HCl of this diazenido complex 8 led to the methyldiazene cation [OsCl(CH₃NNH)(η⁶-p-cymene)L}]⁺ (9⁺). The complexes were characterised spectroscopically and by X-ray crystal structure determination of [OsCl(η⁶-p-cymene)(PhNHNH₂){PPh(OEt)₂}]BPh₄ (6b) and [Ru(κ²–O₂CCH₃)(η⁶-p-cymene){PPh(OEt)₂}]BPh₄ (7b).