Efficient guanylation of N,N-difunctionalized polyamines at the secondary amino functions

Treatment of N^α,N^ω-ditritylated linear and aromatic polyamines and of polyamine conjugates of the alkaloid kukoamine A (KukA) type with N,N′-bis(tert-butoxycarbonyl)thiourea in the presence of Mukaiyama’s reagent produced high yields of derivatives guanylated at the secondary amino functions.     

Reaction of thiourea with formaldehyde and simplest aliphatic diamines

N,N′-Bis(hydroxymethyl)thiourea reacted with propane-1,3-diamine at a molar ratio of 2 : 1 to give 5,5′-propane-1,3-diylbis(1,3,5-triazinane-2-thione), whereas 1,3,5,7,11,13,15,17-octaazatricyclo[15.3.1.1^7,11]-docosane-4,14-dithione was obtained in the reaction with equimolar amounts of the reactants. Tricyclic product was also formed in the three-component condensation of thiourea with formaldehyde and propane-1,3-diamine at a ratio of 1 : 3 : 1. The reactions of N,N′-bis(hydroxymethyl)thiourea with ethane-1,2-diamine (2 : 1) and of thiourea with formaldehyde and butane-1,4-diamine (1 : 2 : 1) afforded 5,5′-(ethane-1,2-diyl)bis(1,3,5-triazinane-2-thione) and 5,5′-(butane-1,4-diyl)bis(1,3,5-triazinane-2-thione), respectively.     

Two chiral mononuclear and one-dimensional cadmium(II) complexes constructed by (1R,2R)-N1,N2-bis(pyridinylmethyl)cyclohexane-1,2-diamine derivatives: Effect of positional isomerism

Reactions of (1R,2R)-N¹,N²-bis(pyridinylmethyl)cyclohexane-1,2-diamine derivatives, (1R,2R)-2-bpcd and (1R,2R)-3-bpcd [(1R,2R)-2-bpcd = (1R,2R)-N¹,N²-bis(pyridin-2-ylmethyl)cyclohexane-1,2-diamine, (1R,2R)-3-bpcd = (1R,2R)-N¹,N²-bis(pyridin-3-ylmethyl)cyclohexane-1,2-diamine], with CdI₂ in an analogous way led to the formation of a chiral discrete mononuclear complex and a chiral one-dimensional polymeric chain, respectively, which may be attributed to the positional isomerism of the ligands. The chiral organic ligands and complexes display luminescent properties indicating that they may have a potential application as optical materials. Powder second-harmonic generation (SHG) efficiency measurement shows that the SHG efficiency of the complexes is approximately 0.3 and 0.45 times that of KDP, respectively.     

Aminomethylation of Thiourea with Formaldehyde and Cyclic Amines

Three-component condensation of thiourea with equimolar amounts of formaldehyde and morpholine afforded N-(morpholin-4-ylmethyl) derivative, whereas analogous reaction with 2 equiv of formaldehyde and amine gave symmetrical N,N′-bis(morpholin-4-ylmethyl)thiourea. In the condensation of thiourea with piperidine and formaldehyde, only symmetrical N,N′-bis(piperidin-1-ylmethyl)thiourea was isolated, regardless of the reactant ratio.     

An effective method for the preparation of mono N-alkyl derivatives of 1,1′-bis(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline)

The condensation of 1,1′-bis(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) with alkyl, aralkyl and aryl aldehydes, but not ketones, in ethanol or chloroform provides useful cyclic aminal [8-substituted 5,6,10,11,15b,15c-hexahydro-2,3,13,14-tetramethoxy-8H-imidazo[5,1-a:4,3-a′]diisoquinoline] intermediates that when subsequently treated with sodium cyanoborohydride in ethanol, followed by the addition of 2 M hydrochloric acid, gave monosubstituted N-alkyl 1,1′-bis(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) derivatives in very high yields. The rates of the initial condensation with four different aldehydes were measured, and the entire sequence was successfully applied in one example to a ‘one-pot’ process; this signals a versatile route to differentially N-substituted 1,1′-bis(1,2,3,4-tetrahydroisoquinoline) derivatives.     

Organocatalytic asymmetric addition of aliphatic thiols to nitro olefins and nitrodienes

The N-3,5-bis(trifluoromethyl)phenyl thiourea derivative of readily available chiral 1-benzyl-3-aminopyrrolidine was an effective organocatalyst for the asymmetric sulfa-Michael reaction. The adducts of aliphatic thiols to nitro olefins and nitrodienes were formed in good yields and with up to 87% ee in the presence of 2.5 mol % of the organocatalyst.     

Reductive alkylation of thioureas: a highly practical synthesis of unsymmetrical N,N′-disubstituted thioureas

A highly practical synthesis of unsymmetrical N,N′-disubstituted thioureas by the reductive alkylation of N-monosubstituted thioureas with aldehydes is described. N-Monosubstituted thioureas can in turn be synthesized by the reductive amination of thiourea with an appropriate aldehyde. This reductive alkylation methodology was also extended to carbamates.     

Fluorimetric determination of aromatic aldehydes with 2,2'-dithiobis(1-aminonaphthalene)

A sensitive fluorimetric method for the determination of aromatic aldehydes is based on their reaction in dilute sulfuric acid with a new reagent, 2,2'-dithiobis(l-amino-naphthalene) in the presence of tri-n-butylphosphine, sodium sulfite and sodium phosphite at ambient temperature. The fluorescences produced are fairly characteristic of individual aldehydes. The method is extremely selective for aromatic aldehydes and very sensitive, especially for p-hydroxybenzaldehyde, o-methoxybenzaldehyde, p-methoxybenzaldehyde and p-tolualdehyde which can be determined at concentrations of as little as 3–5 ng ml^-1.     

Ferromagnetic interaction in iron(II)–bis-Schiff base complexes

The preparation and magnetic properties of three Fe(II)–bis-Schiff base complexes, [Fe₂(L1)2(4,4′-bpy)] · MeOH (1), [Fe(L2)(EtOH)] (2) and [Fe(L3)(MeOH)] (3) (L1 = N,N′-bis(2-hydroxy-1-naphthaldehyde)-1,2-phenylenediimine; L2 = N,N′-bis(salicylidene)-1,2-phenylenediamine; L3 = N,N′-bis(5-Cl-salicylidene)-1,2-phenylenediamine; 4,4′-bpy = 4,4′-bipyridine) are reported. X-ray single crystal structure analyses for 1–3 reveal that 1 shows a dinuclear Fe(II)–bis-Schiff base complex bridged by 4,4′-bpy, while 2 and 3 show mononuclear structures. Molecular packing of 2 shows a uniform one-dimensional chain structure through hydrogen bonds and Fe?π interaction and that of 3 indicates significant π–π interaction to form a dimmer structure. The χT–T plots of 1–3 show all ferromagnetic interaction at low temperature. The origin of the ferromagnetic interaction observed in 2 is tentatively ascribed to the dimer formation through Fe?π interaction at low temperature.     

Reactions of diphenyl- and diethylphosphinodithioic acids with <Emphasis Type="Italic">N</Emphasis>-alkyl-2-haloaldimines in the synthesis of new P,S- and N,P,S-containing organic compounds

Diphenyl- and diethylphosphinodithioic acids, unlike the stronger О,О-dialkyl phosphorodithioic acids, react with N-alkyl-2-chloroaldimines at a 1: 1 ratio, following two pathways: nucleophilic substitution of chlorine in the primary salt by the phosphinothioylthio group and reduction of the cation of the primary salt on the C–Cl bond. Nucleophilic substitution contributes more in the case of the stronger diphenylphosphinodithioic acid, as well as in the case of a large excess of the starting chlorimine. N-Alkyl-2-bromoaldimines react only by a single pathway, specifically, reducing the cation of the primary iminium salt on the C–Br bond. New iminium salts were synthesized and converted into the corresponding aldehydes and imines. The aldehydes synthesized were converted into acetals and five-membered heterocyclic compounds.     

Three-component condensations of aldehydes with N-methoxycarboxamides

The first condensations of N-methoxycarboxamides (component A) with aliphatic acetals (component B) are described. Depending upon the conditions, the hemiaminal type products (AB) can usually be isolated. Conducting the condensations with 2 equiv of acetal affords β-(N-methoxy)amido aldehydes (type ABB products). A condensation using anisole (component C) afforded a product of type ABC.     

Copper(I) complexes of heterocyclic thiourea ligands

The coordination of heterocyclic thiourea ligands (L = N-(2-pyridyl)-N′-phenylthiourea (1), N-(2-pyridyl)-N′-methylthiourea (2), N-(3-pyridyl)-N′-phenylthiourea (3), N-(3-pyridyl)-N′-methylthiourea (4), N-(4-pyridyl)-N′-phenylthiourea (5), N-(2-pyrimidyl)-N′-phenylthiourea (6), N-(2-pyrimidyl)-N′-methylthiourea (7), N-(2-thiazolyl)-N′-methylthiourea (8), N-(2-benzothiazolyl)-N′-methylthiourea (9), N,N′-bis(2-pyridyl)thiourea (10) and N,N′-bis(3-pyridyl)thiourea (11)) with CuX (X = Cl, Br, I, NO₃) has been investigated. CuX:L product stoichiometries of 1:1–1:5 were found, with 1:1 being most common. X-ray structures of four 3-coordinate mononuclear CuXL₂ complexes (CuCl(6)₂, CuCl(7)₂, CuBr(6)₂, and CuBr(9)₂) are reported. In contrast, CuBr(1)₂ is a 1D sulfur-bridged polymer. CuIL structures (L = 7, 8) are 1D chains with corner-sharing Cu₂(μ-I)₂ and Cu₂(μ-S)₂ units, and CuCl(10) is a 2D network having μ-Cl and N-/S-bridging L. Two [CuL₂]NO₃ structures are reported: a mononuclear 4-coordinate copper complex with chelating ligands (L = 10) and a 1D link-chain with N-/S-bridging L (L = 3). Two ligand oxidative cyclizations were encountered during crystallization. CuI crystallized with 6 to produce zigzag ladder polymer [(CuI)₂(12)]·½CH₃CN (12 = N-(pyrimidin-2-yl)benzo[d]thiazol-2-amine) and CuNO₃ crystallized with 10 to form [Cu₂(NO₃)(13)₂(MeCN)]NO₃ (13 = dipyridyltetraazathiapentalene).     

Carbazole-modified blue light-emitting copolymers with the backbones integrated by diphenyloxadiazole,fluorene, and triphenylamine

Two new blue light-emitting polymers, poly{[2,5-bis(4-phenylene)-1,3,4-oxadiazole]-[9,9-dihexylfluorene-2,7-diyl]-[N-(4-(9H-carbazol-9-yl)phenyl)-N,N-bis(p-phenylene)aniline]} (POFPA) and poly{[2,5-bis(4-phenylene)-1,3,4-oxadiazole]-[9,9-dihexylfluorene-2,7-diyl]-[4-(3,6-(di-9H-carbazol-9-yl)-9H-carbazol-9-yl)-N,N-bis(p-phenylene)-aniline]} (POFCPA), were synthesized by Suzuki coupling reactions. By GPC analysis against a linear polystyrene standard POFPA and POFCPA were found to have M_n of 1.68 × 10⁴ and 3.70 × 10³, respectively. In contrast to POFPA, the main absorption peak of POFCPA in dilute toluene solution was blue-shifted by Δλ = 26 nm owing to its backbone of relatively shorter π-conjugation length and more carbazole units in side chain. The absolute fluorescence quantum yield (Φ_f) of POFCPA in dilute toluene solution was determined as 73%, much higher than that of POFPA (Φ_f ≈ 58.9%) measured under the same conditions. An electroluminescence device based on POFCPA displays a stable blue emission having color coordinates of (0.15, 0.20), a maximum brightness of 4762 cd/m², and a maximum current efficiency of 1.79 cd/A. By using this polymer as the host material doped with 1 wt.% 4,4′-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl, the achieved highest brightness, maximum current efficiency and maximum power efficiency are 13,613 cd/m², 3.38 cd/A, and1.84 lm/W, respectively.     

Regio- and diastereoselective SN2′ or SN2″ reactions on chiral acetals of cyclic aldehydes promoted by PhCu,BF3

The regio- and diastereoselectivity of the addition of PhCu, BF₃ reagent on chiral acetals derived from several mono or dienic aldehydes was studied. It was found that monoethylenic acetals react regio- and diastereoselectively via an overall anti S_N2′ reaction. The regioselectivity observed with the dienic acetals seems to be strongly dependent on the nature of the acetal. In all cases the S_N2″reaction was the result of an anti process.     

Heptanuclear high-spin complex compounds based on S-donors

The precursors [Fe(III)(^SYL)Cl] (^SYLH₂) = N,N′-bis(1-hydroxy-Y-2-benzyliden)-1,6-diamino-3-thiohexane, (Y = H, 3EtO, 5Me) are high-spin (S = 5/2) complexes. The precursors are combined with [Fe(II)(CN)₆]⁴⁻ and [Co(III)(CN)₆]³⁻ to yield star-shaped heptanuclear clusters, [Fe(II)(CN–Fe(III)^SYL)₆]Cl₂ and [Co(III)(CN–Fe(III)^SYL)₆]Cl₃. The star-shaped compounds are high-spin (HS) systems at room temperature. On cooling to 20 K some of the iron(III) centers perform some HS–HS transition.     

Co2(CO)8-catalyzed carbonylation of acetals using N-silylamines

Formaldehyde dialkyl acetals and cyclic acetal, 1,3-dioxolane, are smoothly carbonylated using N-silylamines at 140–160 °C under 70–88 kg cm⁻² CO pressure in the presence of a catalytic amount of Co₂(CO)₈ to give the corresponding 2-alkoxyamides in moderate to good yields. In the carbonylation of formaldehyde dialkyl acetals using N-silylamines, addition of pyridine drastically enhances the catalytic activity.     

Catalytic-kinetic determination of substituted thioureas and thioacetamide by an absorptiostat method with bromopyrogallol red/hydrogen peroxide as the indicator reaction

In the absorptiostat method described, the concentration of the dyestuff in the bormopyrogallol red/hydrogen peroxide reaction is kept very low and constant by the automatic addition of increments of bromopyrogallol red solution. This is used in aqueous solutions at pH 4.0 to determine the catalysts thiourea, N-methylthiourea, N-allylthiourea and thioacetamide in the 0.1–1 mmol l^?1 range with only 0.5-ml samples. The catalytic activities of another nine substituted thioureas are described; they depend on the kind of N-substituents as has been shown before for the sodium azide/iodine reaction, but the sequence of activities for different compounds is quite different.     

Recovery and pre-concentration of gold onto poly((N-(Hydroxymethyl)methacrylamide)–1-allyl-2-thiourea) hydrogels synthesized by gamma radiation

Poly((N-(Hydroxymethyl)methacrylamide)–1-allyl-2-thiourea) hydrogels, Poly(NHMMA–ATU), were synthesized by gamma radiation using ⁶⁰Co γ source at different irradiation doses and different ATU content in the irradiated monomer mixture. The swellability of the synthesized hydrogels was changed by irradiation doses and by the content of ATU in the irradiated mixture. These hydrogels were used for the specific gold recovery and pre-concentration from single gold ion solutions and from different natural samples. It has been observed that gold adsorption capacity onto the hydrogels was high at low pHs and reached maximum value at pH = 0.5. Adsorption capacity of the hydrogels for gold at pH = 0.5 was found to be about 698 mg g^− 1 dry hydrogels. Adsorption equilibrium time of gold ions onto the hydrogels was found to be very short and also these hydrogels were showed extremely high selectivity to the gold ions in acidic media when the concentration of the other metal ions were extremely higher than gold. Because of the high specificity of these hydrogels to gold beside the other metal ions at low pHs, all matrix effects were easily eliminated adsorbing gold onto the hydrogels and desorbing into 3 M HCl solution containing 0.8 M thiourea. These hydrogels were found to be highly open pore size. This property of the hydrogels make them attractive due to high adsorption capacity of gold ions on/in the hydrogels penetrating inside and react to all functional groups in the interior surface of the hydrogels.     

A convenient method for the synthesis of (Z)-α-haloacrylates: Lewis base-catalyzed carbonyl olefination using α-halo-C,O-bis(trimethylsilyl)ketene acetals

A highly useful method for the stereoselective synthesis of (Z)-α-haloacrylates from various aldehydes that uses α-halogenated ethyl-C,O-bis(trimethylsilyl)ketene acetals in the presence of a Lewis base catalyst such as acetate salts was established. This procedure gives the corresponding α-halo-α,β-unsaturated esters in high yields with excellent stereoselectivity from E/Z mixtures of ketene silyl acetals under mild conditions.     

Access to C-protected β-amino-aldehydes via transacetalization of 6-alcoxy tetrahydrooxazinones and use for pseudo-peptide synthesis

Efficient access to masked β-amino-aldehydes was performed starting from 6-alcoxy tetrahydrooxazinone 6a–d (6-ATO). Transacetalization leads to the opening of the cycle to form either unsymmetric acetal 7 or symmetric acetals 16–18. These amino acetals are key compounds, obtained with 99% ee, which can be engaged in efficient peptide coupling. This method could easily provide peptides aldehydes or small amido aldehydes as exemplified with the formal synthesis of ent-Maraviroc.