Two closely related {4‐[(N‐substituted amino)(diethoxyphosphoryl)methyl]phenyl}boronic acids

Organic phosphonic acids and organic phosphonic acid esters have been of much interest due to their applications in the fields of medicine, agriculture and industrial chemistry. Boronic acids can act as synthetic intermediates and building blocks and are used in sensing, protein manipulation, therapeutics, biological labelling and separation. The additional introduction of an aminophosphonic acid group into a boronic acid may give new opportunities for application. To study the structure of such multifunctional compounds, we prepared two new derivatives which can be easily converted to the corresponding phosphonic acids. In the title compounds, {4‐[(butylamino)(diethoxyphosphoryl)methyl]phenyl}boronic acid monohydrate, C₁₅H₂₇BNO₅P·H₂O, (I), and {4‐[(diethoxyphosphoryl)(4‐nitroanilino)methyl]phenyl}boronic acid, C₁₇H₂₂BN₂O₇P, (II), three different substituents are attached to a central C—H group, namely 4‐boronophenyl, diethoxyphosphoryl and amine. Compound (I) crystallizes as a monohydrate and O_B—H…N hydrogen bonds link neighbouring molecules into chains along the [001] direction. The solvent water molecule connects two such chains running in opposite directions. Compound (II) crystallizes as an ansolvate and classical hydrogen bonds result in a layer structure in the (001) plane.     

3-(Furyl)-3-(diethoxyphosphoryl)acrylates: Synthesis and reaction with nitromethane

A series of 3-(furyl)-3-(diethoxyphosphoryl)acrylates was synthesized by the reaction of 2- and 3-furoyl phosphonates with ethoxycarbonylmethylenetriphenylphosphorane. It was shown that in all cases diethoxyphosphoryl and ester groups were in trans-position with respect to the double bond disregarding the structure of the furan fragment. Potassium fluoride catalyzed addition of nitromethane to the compounds synthesized was studied. It was found that this reaction proceeded regioselectively to form 2-[(furyl)(diethoxyphosphoryl) methyl]-3-nitropropanoic acids.     

Synthesis and some heterocyclization reactions of new diethyl (1,1-difluoro-3,3-dicyano-2-trifluoromethylallyl)phosphonate and ethyl 3,3-dicyano-2-[(diethoxyphosphoryl)difluoromethyl]acrylate

A new CF₂X-analogue of 1,1-bis(trifluoromethyl)-2,2-dicyanoethylene (X = P(O)(OEt)₂), diethyl (1,1-difluoro-3,3-dicyano-2-trifluoromethylallyl)phosphonate, has been synthesized from diethoxyphosphoryl pentafluoroacetone 1. A similar phosphoryl analogue of ethyl 3,3-dicyano-2-trifluoromethylacrylate, ethyl 3,3-dicyano-2-[(diethoxyphosphoryl)difluoromethyl]acrylate, has been obtained from ethyl 3-(diethoxyphosphoryl)-3,3-difluoro-2-oxopropionate 2. By heterocyclization of these new ethylenes with 3-methyl-2-pyrazoline-5-ones, 3(5)-aminopyrazoles, dimedone, 2-aminopyridines, 1-aryl-3-methyl-5-aminopyrazoles, 1,3,3-trimethylisoquinolines, as well as by condensation with anilines and ketones, the difluoromethylphosphonate-substituted derivatives of 1,4-dihydropyrano[2,3-c]pyrazole, 4,5-dihydropyrazolo[1,5-a]pyrimidine, 5,6,7,8-tetrahydro-4H-chromene, 2H-pyrido[1,2-a]pyrimidine, 4,7-dihydro-1H-pyrazolo[3,4-b]pyridine, 1,4-dihydropyridine, 4,5,6,7-tetrahydro-1H-[1]pyrindine, 1,4,5,6,7,8-hexahydroquinoline, and 6,7-dihydro-2H-pyrido[2,1-a]isoquinoline have been obtained in one stage.     

Alkenylphosphonates: unexpected products from reactions of methyl 2-[(diethoxyphosphoryl)methyl]benzoate under Horner-Wadsworth-Emmons conditions

Methyl 2-[(diethoxyphosphoryl)methyl]benzoate reacts with several aldehydes to produce an alkenylphosphonate as the major product, together with varying amounts of the expected Horner-Wadsworth-Emmons product, a 1,2-disubstituted E-alkene. Use of a bulky aldehyde or the tert-butyl ester favours the normal HWE product.     

Theoretical study on electronic structures,spectra, and charge transporting properties of two Pt(II) complexes with triazenido ligands

Russian Journal of General Chemistry - Two compounds 1-[(2-carboxymethyl)benzene]-3-[2-pyridine]triazene (HL) and 1-[(2-carboxymethyl) benzene]-3-[o-aminobenzoic acid]triazene (H2L') and two...     

Simple synthesis of some unsaturated 1,1-difluoro-2-hydroxyethylphosphonates

A short synthesis of some 1,1-difluoro-2-hydroxymethylphosphonates in good yields is described. This procedure involves the regioselective 1,2-addition of [(diethoxyphosphoryl)difluoromethyl]lithium toward unsaturated aldehydes and ketones.     

Anions derived from squaric acid form interionic pi-stack and layered, hydrogen-bonded superstructures with organometallic sandwich cations: the magnetic behaviour of crystalline

Depending on the stoichiometric ratio, squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione, H2SQA) reacts with [(eta6-C6H6)2Cr] in THF to form the crystalline material [(eta6-C6H6)2Cr][HSQA] (1) and in water to yield [[(eta6-C6H6)2Cr]2][SQA] x 6H2O (3); it also reacts with [(eta5-C5H5)2Co][OH] in water to form [[(eta5-C5H5)2Co]2][SQA] x 6H2O (4). Compound 1 is almost isostructural with the previously reported salt [(eta5-C5H5)2Co][HSQA] (2); its structure is based on pi-pi stacks between the benzene ligands and the hydrogen squarate anionic chains (pi-pi distance 3.375 A). Compounds 3 and 4 are isomorphous and have a structure in which layers of organometallic cations intercalate with layers of water molecules hydrogen bonded to squarate dianions. All crystals contain charge-assisted C-Hdelta+...Odelta- hydrogen bonds between the organometallic and the organic components, while negative O-H(-)...O(-) and O-H...O(2-) interactions are present in the pairs 1/3 and 2/4, respectively. In constrast to most organic salts of [(eta6-C6H6)2Cr]+ and [(eta5-C5H5)2Co]+ which are yellow, crystals of compounds 1-4 are orange. Reflectance spectra measured on the crystalline material 1 show the presence of an intense tail that can be assigned to a charge-transfer transition through the [(eta6-C6H6)2Cr]+/[HSQA]- pi-stacking interactions, while the pi stacking in 2 causes only a broadening of the band. The magnetic behaviour of 1 and 3 has been investigated by SQUID magnetometry. Both compounds are characterised by a weak antiferromagnetic interaction between the S=1/2 Cr centres of the [(eta6-C6H6)2Cr]+ cations, which is significantly stronger in 1 due to the pi-stacking with the HSQA- anions.     

Dynamic mechanism of E2020 binding to acetylcholinesterase: a steered molecular dynamics simulation

The unbinding process of E2020 ((R,S)-1-benzyl-4-[(5,6-dimethoxy-1-indanon)-2-yl]-methylpiperidine) leaving from the long active site gorge of Torpedo californica acetylcholinesterase (TcAChE) was studied by using steered molecular dynamics (SMD) simulations on a nanosecond scale with different velocities, and unbinding force profiles were obtained. Different from the unbinding of other AChE inhibitors, such as Huperzine A that undergoes the greatest barrier located at the bottleneck of the gorge, the major resistance preventing E2020 from leaving the gorge is from the peripheral anionic site where E2020 interacts intensively with several aromatic residues (e.g., Tyr70, Tyr121, and Trp279) through its benzene ring and forms a strong direct hydrogen bond and a water bridge with Ser286 via its O24. These interactions cause the largest rupture force, approximately 550 pN. It was found that the rotatable bonds of the piperidine ring to the benzene ring and dimethoxyindanone facilitate E2020 to pass the bottleneck through continuous conformation change by rotating those bonds to avoid serious conflict with Tyr121 and Phe330. The aromatic residues lining the gorge wall are the major components contributing to hydrophobic interactions between E2020 and TcAChE. Remarkably, these aromatic residues, acting in three groups as "sender" and "receiver", compose a "conveyer belt" for E2020 entering and leaving the TcAChE gorge.     

Synthesis of chiral hydroxyl phospholanes from D-mannitol and their use in asymmetric catalytic reactions

Chiral hydroxyl monophosphane 3 [(2S,3S,4S,5S)-3,4-dihydroxy-2, 5-dimethyl-1-phenylphospholane] and bisphospholanes 5a [1,2-bis[(2S, 3S,4S,5S)-3,4-dihydroxy-2,5-dimethylphospholanyl]benzene] and 5b [1, 2-bis[(2S,3S,4S,5S)-2,5-diethyl-3,4-dihydroxyphospholanyl]benzene] were synthesized from readily available D-mannitol in high yields. Strategies for protection and deprotection of OH-groups in the presence of phosphines have been explored. Rate acceleration in the Baylis-Hillman reaction was observed when a hydroxyl phosphine was used as the catalyst. Rhodium complexes with chiral bisphospholanes are highly enantioselective catalysts for the asymmetric hydrogenation of various kinds of functionalized olefins such as dehydroamino acid derivatives, itaconic acid derivatives, and enamides. An interesting feature of the hydroxyl phospholane system is that hydrogenation of some substrates can be carried out in water with >99% ee and 100% conversion (e.g., itaconic acid).     

2,5-Dimethyl-3,4-bis[(2R,5R)-2,5-dimethylphospholano]thiophene: first member of the hetero-DuPHOS family

[reaction: see text] The 2,5-dimethyl-3,4-bis[(2R,5R)-2,5-dimethylphospholano]thiophene (UlluPHOS), a new thiophene-based analogue of (R,R)-1,2-bis(phospholano)benzene (Me-DuPHOS), was synthesized, geometrically and electronically characterized, and employed as ligand of Rh and Ru in some standard hydrogenation reactions of prostereogenic functionalized carbon-carbon and carbon-oxygen double bonds. The synthesis of UlluPHOS is much easier than that provided for Me-DuPHOS. UlluPHOS and Me-DuPHOS display very similar geometries, while the electronic availability of the former is higher than that exhibited by the latter. The Rh and Ru complexes of UlluPHOS produced excellent enantiomeric excesses (98.9-99.5%) in the hydrogenation of N-acetyl-alpha-enamino acids and reaction rates higher than those found when employing the analogous complexes of Me-DuPHOS.     

Synthesis of substituted in benzene ring 4-[(2-aminophenyl)thio]-, 4-[(2-mercaptophenyl)amino]-2-methylquinolines and (4E)-4-[(2-mercaptophenyl)imino]-2-methyl-1,4-dihydroquinolines

By a reaction of 2-methyl-4-chloroquinolines with o-mercaptoaniline under various conditions synteses were performed of substituted in the benzene ring 4-[(2-aminophenyl)thio]-2-methylquinolines and (4E)-4-[(2-mercaptophenyl)imino]-2-methyl-1,4-dihydroquinolines that were respectively by isomerization or rearrangement converted into 4-[(2-mercaptophenyl)amino]-2-methylquinolines.     

Synthesis and crystal structures of the first C2-symmetric bis-aldimine NCN-pincer complexes of platinum and palladium

(S,S)-2,6-bis[(N-α-methylbenzyl)imino]phenylpalladium bromide was synthesised by oxidative addition of palladium(0) to (S,S)-1-bromo-2,6-bis[(N-α-methylbenzyl)imino]benzene. In contrast, (S,S)-2,6-bis[(N-α-methylbenzyl)imino]phenylplatinum chloride was synthesised by direct C-H activation from the reaction of potassium tetrachloroplatinate with (S,S)-1,3-bis[(N-α-methylbenzyl)imino]benzene. The X-ray crystal structures of both pincer complexes were obtained. Treatment of both complexes with silver hexafluoroanimonate gave effective but not stereoselective catalysts for a Michael reaction between methyl vinyl ketone and methyl 2-cyanopropanoate.     

Reactions of 1,4-bis(tetrazole)benzenes: formation of long chain alkyl halides

The reactions of 1,4-bis[2-(tributylstannyl)tetrazol-5-yl]benzene with α,ω-dibromoalkanes were carried out in order to synthesise pendant alkyl halide derivatives of the parent bis-tetrazole. This led to the formation of several alkyl halide derivatives, substituted variously at N1 or N2 on the tetrazole ring. The crystal structures of 1,4-bis[(2-(4-bromobutyl)tetrazol-5-yl)]benzene (2-N,2-N′), 1,4-bis[(2-(4-bromobutyl)tetrazol-5-yl)]benzene (1-N,2-N′) and 1,4-bis[(2-(8-bromooctyl)tetrazol-5-yl)]benzene (2-N,2-N′) are reported. Further discussion involves the structure of 1,4-bis[2-(6-bromohexyl)-2H-tetrazol-5-yl]benzene (2-N,2-N′) previously reported.     

Participation of benzene hydrogen bonding upon anion binding

A m-xylene-bridged imidazolium receptor, 1, has been designed and synthesized. The receptor 1 utilizes two imidazole (C-H)(+)- - -anion hydrogen bonds and one benzene hydrogen- - -anion hydrogen bond. The major driving force of complexation between the receptor 1 and anions comes from two imidazole (C-H)(+)- - -anion hydrogen bonds. However, both NMR experiments and ab initio calculations show that the benzene hydrogen attracts the anion guests, clearly indicating benzene (C-H)- - -anion hydrogen bonding. [reaction: see text]     

Insertion of the Ga(I) bis-imidinate Ga(DDP) into the metal halogen bonds of Rh(I) complexes. How electrophilic are coordinated Ga(DDP) fragments?

The reactivity of Ga(DDP) (DDP = 2-((2,6-diisopropylphenyl)amino-4-((2,6-diisopropylphenyl)imino)-2-pentene) towards the rhodium-chloride bonds of [RhCl(PPh3)3] and [RhCl(COE)2]2 (COE = cyclooctene) is investigated. Reaction of the first complex leads to [(Ph3P)2Rh{Ga(DDP)}(mu-Cl)] (1), exhibiting a chloride bridging the gallium and the rhodium atoms, whereas the second complex leads to a full insertion of the Ga(DDP) ligand into the Rh-Cl bond giving [(COE)(benzene)Rh{(DDP)GaCl}] (2) on coordination of the solvent C6H6. Compounds 1 und 2 readily react with the halide abstracting reagent Tl[BArF] (BArF = B[3,5-(CF3)2C6H3]4), yet the products could not be isolated and characterized because of their lability. The Au(I) complex [{(DDP)Ga}Au{Ga(DDP)}Cl] reacts with Na[BArF] giving the linear, symmetric cationic complex [{(DDP)Ga.THF}2Au][BArF] (3.2THF), exhibiting two THF molecules coordinated to the Ga(DDP) moieties.     

Facile Ar-CF3 bond formation at Pd. Strikingly different outcomes of reductive elimination from [(Ph3P)2Pd(CF3)Ph] and [(Xantphos)Pd(CF3)Ph

Facile and highly selective perfluoroalkyl-aryl reductive elimination from a metal center (Pd) has been demonstrated for the first time. At temperatures as low as 50-80 degrees C, [(Xantphos)Pd(Ph)CF3] undergoes remarkably clean decomposition to produce CF3Ph in high yield and selectivity. In contrast, analogous trifluoromethylpalladium aryls stabilized by rigid cis-chelating ligands such as dppe are completely unreactive at temperatures up to 130-140 degrees C. Decomposition of [(Ph3P)2Pd(Ph)CF3] in the presence of PhI in benzene at 60 degrees C does not produce PhCF3 but rather leads to [(Ph3P)2Pd(Ph)I] and [Ph4P]+[(Ph3P)Pd(CF3)3]- in a 2:1 ratio with high selectivity.     

Reduktion von 1,2-bis[(Z)-(2-nitrophenyl)-NNO-azoxy]benzol: Synthese von Cyclotrisazobenzol ( = (5E,6aZ,11E,12aZ,17E,18aZ)-5,6,11,12,17,18-Hexaazatribenzo[aei][1,3,5,7,9,11]cyclododeca-hexaen)

Reduction of 1,2-Bis[(Z)-(2-nitrophenyl)-NNO-azoxy]benzene¹: Synthesis of Cyclotrisazobenzene ( = (5E,6aZ,11E,12aZ,17E,18aZ)-5,6,11,12,17,18-Hexaazatribenzo[aei][1,3,5,7,9,11]cyclododeca-hexaene) Na₂S reduction of 1,2-bis[(Z)-(2-nitrophenyl)-NNO-azoxy]benzene ( 2 ) yielded 3 deoxygenated products: the (known) red 2,2′-((E,E)-1,2-phenylenbisazo)dianiline ( 3 , 23%), the orange 2-[2-((E)-2-aminophenylazo)phenyl]-2H-benzotriazol ( 4 , 55%) and the colorless 2,2′-(1,2-phenylene)di-2H-benzotriazol ( 5 , 13%). The constitutions of 3 – 5 and of 6 , the N-acetyl derivative of 4 , were deduced from their ¹H-NMR spectra (chemical shifts, couplings, and symmetry properties), and the configurations of 3 , 4 , and 6 at their N,N-double bonds are assumed to be the same as in 2 . Oxidation of 3 with 2 mol-equiv. of Pb(OAc)₄ afforded 5 (47%) and a novel, highly symmetrical macrocycle, called cyclotrisazobenzene ( 7 , 24%). The constitution of 7 as a tribenzo-hexaaza[12]annulene and its (E)-configuration at the N,N-bonds was confirmed by X-ray analysis. The molecular symmetry expressed by the ¹H-, ¹³C- and ¹⁵N-NMR spectra of 7 reveals a rapid torsional motion around the six N,C bonds. This implies that the N,N-double bonds in the cyclic 12π-electron system (or 24π-electron system if the benzene rings are included) of 7 are highly localized.     

Metal-metal and carbon-carbon bonds as potential components of molecular batteries

The reductive coupling of [M(salophen)] derivatives, where M is an early transition metal and salophen is N,N'-o-phenylenebis(salicylideneaminato) dianion, led to the formation of dimers linked through C-C and M-M bonds. Both of these bonds can potentially function as electron reservoirs: each bond can be used as a reversible source of a pair of electrons under the condition that it is not chemically transformed by the incoming substrate which functions as an electron acceptor. To explore this potential function as well as the competition in the redox processes between C-C and M-M bonds within the same molecular framework, we investigated the reduction of [(tBu4-salophen)NbCl3] (1) and [(tBu4-salophen)MoCl2] (7) as model compounds. In the former case, the reduction led to [(Nb-Nb)(tBu4-*salophen2*)] (2) which contains both a Nb-Nb bond (2.6528(7) A) and two C-C bonds across two imino groups of the ligand. Complex 2 can be reduced further to a transient compound 5 that contains an Nb=Nb bond. In the second case, the reduction of 7 by two electrons led to [(Mo[triplebond]Mo)(tBu4-salophen)2] (8), which does not contain any C-C linkages between the two salophen units. Complexes 2 and 5 are able to transfer one pair and two pairs of electrons, respectively, to give compounds 3, 4, and 6, with the consequent cleavage of the Nb-Nb and Nb=Nb bonds. In the present case, it is surprising that the C-C bonds do not participate in the reduction of the substrates. A careful theoretical treatment anticipates, both in the case of 1 and 7, the preferential formation of metal-metal bonds upon reduction. This is indeed the case for 7, but not for 1, where the formation of C-C bonds competes with that of M-M bonds, the latter being the first ones, however, to be involved in electron-transfer reactions. The theoretical approach allowed us to investigate the possibility of intramolecular electron transfer from C-C bonds to M-M bonds and vice versa.     

Polynaphthylimides based on isomeric 2,5-bis[(aminophenoxy)phenylen]-1,3,4-oxadiazoles

Polynaphthylimides containing 1,3,4-oxadiazole cycles in main chains of macromolecules are prepared via the interaction of isomeric 2,5-bis[(aminophenoxy)phenyl]-1,3,4-oxadiazoles with dianhydrides of naphthalene-1,4,5,8-tetracarboxylic acid and 1,3-bis(1,8-dicarboxynaphthoyl-4)benzene. These polymers are synthesized through high-temperature polycyclocondensation in N-methylpyrrolidone and molten phenol. The relationships between the solubility and thermal characteristics of polynaphthylimides and their structure are studied, and the optical properties of the polymers are estimated.