6‐Propylamino‐2,6‐propylepimino‐2,4,4,8,8‐pentakis(pyrrolidin‐1‐yl)‐1,3,5,7,2λ5,4λ5,6λ5,8λ5‐tetraazatetraphosphorocine

The title compound, C₂₆H₅₅N₁₁P₄, consists of a bicyclic phosphazene ring with five bulky pyrrolidino and one propyl­amino group, together with a second propyl­amino group bridging the two P atoms. The asymmetric unit contains two mol­ecules with very similar conformations. The bulky substituents are instrumental in determining the bicyclic P₄N₅ ring conformation. Each of the fused six‐membered N₃P₃ rings is in a sofa conformation. The P—N distances in the bridge are non‐equivalent and one of them is the longest P—N bond in the mol­ecule. The hybridization of the bridging N atom is pyramidal. The single and double P—N bonds cannot easily be distinguished, since they retain their phosphazenic character in the phosphazene macro‐rings.     

Palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate: a practical synthesis of unsymmetrical ureas

An efficient method for palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate is reported. The protocol allows for the synthesis of unsymmetrical N,N'-di- and N,N,N'-trisubstituted ureas in one pot and is tolerant of a wide range of functional groups. Insight into the mechanism of aryl isocyanate formation was gleaned through studies of the transmetalation and reductive elimination steps of the reaction, including the first demonstration of reductive elimination from an arylpalladium isocyanate complex to produce an aryl isocyanate.     

A guide to Sonogashira cross-coupling reactions: the influence of substituents in aryl bromides, acetylenes, and phosphines

The conversion-time data for 168 different Pd/Cu-catalyzed Sonogashira cross-coupling reactions of five arylacetylenes (phenylacetylene; 1-ethynyl-2-ethylbenzene; 1-ethynyl-2,4,6-R(3)-benzene (R = Me, Et, i-Pr)) and Me(3)SiCCH with seven aryl bromides (three 2-R-bromobenzenes (R = Me, Et, i-Pr); 2,6-Me(2)-bromobenzene and three 2,4,6-R(3)-bromobenzenes (R = Me, Et, i-Pr)) with four different phosphines (P-t-Bu(3), t-Bu(2)PCy, t-BuPCy(2), PCy(3)) were determined using quantitative gas chromatography. The stereoelectronic properties of the substituents in the aryl bromides, acetylenes, and phosphines were correlated with the performance in Sonogashira reactions. It was found that the nature of the most active Pd/PR(3) complex for a Sonogashira transformation is primarily determined by the steric bulk of the acetylene; ideal catalysts are: Pd/P-t-Bu(3) or Pd/t-Bu(2)PCy for sterically undemanding phenylacetylene, Pd/t-BuPCy(2) for 2- and 2,6-substituted arylacetylenes or Me(3)SiCCH and Pd/PCy(3) for extremely bulky acetylenes and aryl bromides. Electron-rich and sterically demanding aryl bromides with substituents in the 2- or the 2,6-position require larger amounts of catalyst than 4-substituted aryl bromides. The synthesis of tolanes with bulky groups at one of the two aryl rings is best done by placing the steric bulk at the arylacetylene, which is also the best place for electron-withdrawing substituents.     

1H and 13C NMR spectral assignment of N,N′‐disubstituted thiourea and urea derivatives active against nitric oxide synthase

The ¹H and ¹³C NMR resonances of seventeen N‐alkyl and aryl‐N′‐[3‐hydroxy‐3‐(2‐nitro‐5‐substitutedphenyl)propyl]‐thioureas and ureas ( 1–17 ), and seventeen N‐alkyl or aryl‐N′‐[3‐(2‐amino‐5‐substitutedphenyl)‐3‐hydroxypropyl]‐thioureas and ureas ( 18–34 ), designed as NOS inhibitors, were assigned completely using the concerted application of one‐ and two‐dimensional experiments (DEPT, HSQC and HMBC). NOESY studies confirm the preferred conformation of these compounds. Copyright © 2016 John Wiley & Sons, Ltd.     

Stereochemistry and opioid receptor affinity of 2,4‐dipyridine‐3,7‐diazabicyclo[3.3.1]nonanones ‐ influence of the substituent in position N7

The stereochemistry the 2,4‐di‐arene substituted 3,7‐diazabicyclo[3.3.1]nonan‐9‐one 1,5‐dicarboxylate skeleton was found to be regulated by the kind of substituents attached to the arene rings as well as to the nitrogens N3 and N7. Conformational isomers, i.e., chair/chair, boat/chair and chair/boat, in addition to cis/trans conflgurational isomerism with respect to the arene rings were reported. Since the analgesic potency of the diazabicyclononanones, which is related to their affinity toward the κ‐opioid receptor, is governed by the stereochemistry of the molecules, the influence of the substituents at nitrogen N7 was studied herein. The various differently N7 substituted diazabicyclononanones were found to crystallise in a highly symmetrical chair/chair conformation. However, beside HZ2 none of the compounds exhibits high affinity to the κ receptor. In contrast, some compounds with affinity to the μ receptor could be identified. In addition, the N7‐(4‐carboxybenzyl) substituted compound was found to have affinity to the δ receptor in the submi‐cromolar range of concentration.     

Effect of allylic strain on the conformations of diphenyl-substituted tetrahydro-1,3-oxazin-2-ones and hexahydropyrimidin-2-ones

The conformations of the cis and trans isomers of 4,6-diphenyl-, 4,5-diphenyl- and 5,6-diphenyltetrahydro-1,3-oxazin-2-one and 4,5-diphenylhexahydropyrimidin-2-one, and of some of their N-substituted derivatives, have been studied by ¹H NMR. Conformers with 4a, 6e-, 4a, 5e- and 5a, 6e-phenyl groups are preferred in the respective isomers of the N-H oxazinones, confirming a half-chair conformation of the ring. Allylic strain caused by N-substituents shifts strongly the a,e?e, a equilibria in trans-4,6-diphenyl- and cis-4,5-diphenyl-oxazinones, but only moderately the e,e?a,a equilibria in the compounds with trans-vicinal phenyl groups. In the latter, the diaxial conformation is preferred only in the case of bulky N-substituents. The diaxial conformation is more favoured in the trans-4,5-diphenylpyrimidones.     

Ab initio study of the (5R)- and (5S)-TT pyrimidine h5(6-4) pyrimidone photoproducts. Implications on the design of new biologically relevant analogues

A computational study of a series of N(1)- and/or C(6)-alkyl-5,6-dihydrothymine diastereomers at theory levels up to MP4(SDTQ)/6-31G//HF/6-31G and MP2/6-311G//HF/6-31G has demonstrated the respective importance of the substituents at positions 1, 5, and 6 on the energetically favored conformation of each isomer. Results obtained both in the gas and condensed phase indicate that unsubstitution of the N(1)-position favors a half-chair conformation with the C(5) -and C(6)-substituents in the equatorial position. On the other hand, in the case of the (6S)-1,6-dimethyl-5,6-dihydrothymine, the C(6)-substituent adopts the axial position to minimize its van der Waals interactions with the N(1)-substituent. Furthermore, if the configuration at the C(5)-dihydrothymine position has no resultant influence on the total molecular free energy, when a pyrimidone substituent is introduced at the dihydrothymine C(6)-position, additional repulsive forces between the C(5)- and C(6)-substituents make the diaxially substituted half-chair conformation the most energetically favorable one. These results indicate that the observed C(6)-axially substituted conformation of the thymine-thymine pyrimidine h(5)(6-4) pyrimidone photoproducts is not necessarily induced by the macrocyclic structure. They also nicely explain the formation mechanism of these photoproduct derivatives, and allow the prediction of the conformation of new analogues.     

The origin of the conformational preference of N,N'-diaryl-N,N'-dimethyl ureas

Poly aromatic ureas and poly aromatic amides are important classes of foldamers-oligomers with well defined conformations. We have explored the origins of the conformational preference of some N,N'-diaryl-N,N'-dimethyl ureas by a combination of NMR spectroscopy and electronic structure calculations using both a recently developed density functional (M06-2X) and a DFT approach (DFT-D) having empirical corrections for dispersive interactions. We have validated the DFT-D approach for structures of this type using high level wavefunction calculations, (CCSD(T)), of the unsubstituted N,N'-diphenyl-N,N'-dimethyl urea. For the N,N'-diaryl-N,N'-dimethyl ureas we have identified a number of 'endo' conformers (i.e. having an E,E geometrical conformation about the two urea C-N bonds), both π- and tert-butyl-stacked, as well as 'exo' structures (having a Z geometrical conformation about at least one of the C-N bonds), and have computed the relative energies of these conformers as well as the barriers for their interconversion. We find that the relative energies of the 'endo' structures closely follow the relative values of the dispersive interactions. The calculations have allowed us to associate different conformers with the various peaks in the NMR spectra, which point to relatively small differences in energy between the conformers. Somewhat larger energy differences are predicted by the two computational approaches, with the M06-2X functional performing the better of the two. It is suggested that the continuum model employed may not be sufficiently accurate to reflect the solvation of the various conformers.     

A computational study of the effectiveness of the frontier molecular orbital formalism in predicting conformational isomerism in (p-RC6H4NC)2W(dppe)2

Ab initio electronic structure calculations on a series of ligands, p-RC6H4NC:, indicate, that the energy of the LUMO correlates with the electron-withdrawing/donating capabilities of the substituent group, which determines the relative pi-acidity of the ligand. Depending on the nature of the para substituent group on the aryl isocyanide ligand, bis(aryl isocyanide) complexes of tungsten-containing bulky bidentate arylphosphine ligands adopt either cis or trans conformations. The frontier molecular orbital formalism predicts that strong pi-acids, which contain electron-withdrawing groups, tend to polarize sufficient charge density away from the metal center to effect the formation of the sterically less favorable but electronically stabilized cis conformer. Density functional theory calculations on similar complexes containing phosphines which do not impose severe steric contraints indicate that the balance between steric and electronic stabilization can be effectively predicted by comparing the relative energies of the ligand LUMOs.     

Dimeric capsules by the self-assembly of triureidocalix

A number of calix[6]arenes bearing ureas at the upper rim positions of alternate rings 1, 3 and 5 were prepared and studied in detail by NMR spectroscopy and gel permeation chromatography. N-Unsubstituted ureas were shown to dimerize through a cyclic array of hydrogen bonds to give cylindrical cavities capable of encapsulating small molecules such as dichloromethane, benzene and fluorobenzene. Slow equilibria between dimer and monomer were observed in [D6]DMSO-CDCl3 mixtures. By contrast, N-substituted ureas are monomeric. All urea monomers with bulky O-substituents display a solvent-dependent, slow equilibrium between C3v and Cs cone conformations.     

The synthesis of novel acetolactate synthase inhibitors,N‐(asymmetrically disubstituted phosphoryl)‐N′‐(4,6‐dimethoxypyrimidin‐2‐yl) ureas

In view of the isosterism of the sulfonyl group(‐SO₂‐) and the phosphoryl group, two new types of compounds N‐(N‐aryl‐O‐alkyl phosphoryl)‐N′‐(4,6‐dimethoxypyrimidin‐2‐yl) ureas (2) and N‐(N‐aryl‐N‐alkylphosphoryl)‐N′‐(4,6‐dimethoxypyrimidin‐2‐yl) ureas (3) were designed and synthesized by treating N‐(arylaminochlorophosphoryl)‐N′‐(4,6‐dimethoxypy‐rimidinyl‐2‐) ureas (4) with alcohols or amines. Compounds 4 were obtained by treating dichloro‐phosphoryl isocyanate with 4,6‐dimethoxy‐2‐amino‐pyrimidine and then with aromatic amines. The enzyme tests in vitro indicated that compounds 2 and 3 were two novel classes of acetolactate synthase (ALS) inhibitors and also showed that phosphoryl groups[‐P(O)(OR)‐, R=alkyl] and [‐P(O)(NHR), R=alkyl] were likely to be good bioisosteres of the sulfonyl group (‐SO₂‐) in the sulfonylureas. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10:237–241, 1999     

1-芳基-2-苯基-3-甲基-3-异丙基-2-氧代-1,4,2-二氮磷杂环戊-5-酮的合成及除草活性

利用取代苯基脲与苯基二氯化膦和3-甲基-2-丁酮进行的类Mannich反应合成了15种新的1,4,2-二氮磷杂环戊-5-酮类化合物(2a_2o), 其结构经     

Curved Perylene Diimides Fused with Seven-Membered Rings

Curved perylene diimides fused with seven-membered rings have been synthesized using a regioselective bay-functionalization method and Pd-catalyzed intramolecular C−H/C−Br coupling reaction. X-Ray analysis and temperature-dependent NMR spectroscopy revealed the curved molecular structure with a certain degree of conformational flexibility. The curved and expanded π-conjugation altered the electronic properties while retaining the intrinsic properties of the parent perylene diimide. Despite the absence of solubilizing N-substituents, the curved perylene diimides showed sufficient solubility for application in solution-processed organic photovoltaic devices. The devices showed superior performance with a power conversion efficiency of up to 2.76% due to suppressed charge recombination. Our detailed investigations suggest that the introduction of a curved structure enables the removal of the bulky N-substituents, which is an effective way to achieve a thin-film morphology suitable for photoelectric conversion.     

Synthesis and Biological Activity of Novel Aryl Sulfamonyl Ureas

2-Substituted aryl sulfamonyl ureas are novel sulfonylurea compounds,in which the bridge was modified. For instance, 1-((o-cyclopropylcarbonyl)phenyl sulfamonyl)-3- (4',6'-dimeth-oxy-2-pyrimidinyl)urea is effective for the selective control of a variety of weed species in the presence of cereal crops and is especially useful for controlling broadleaf weeds and sedges^[1]. For further structural study, nine aryl sulfamonyl ureas(3) were synthesized, including four 1-(o-substituted phenyl sulfamonyl)-3-(4'-substituted pyrimidin-2'-yl) ureas and five 1-(α-pyridinyl sulfamonyl)-3-(4'6'-disubstituted pyrimidin-2'-yl) ureas.     

Synthesis of 2-substituted 1-benzyl-2,3,4,5-tetrahydro-1-benzazepines by palladium catalysis. Observation of a competitive β-hydride elimination pathway

A synthetic route to 1-benzyl-tetrahydro-1-benzazepine is reported, which also permits access to analogous structures with alkyl and aryl substituents at position-2 of the aliphatic ring. Palladium catalysis is utilized in two of the three steps, constructing the seven-membered rings effectively from 2-bromoiodobenzene. Competitive β-hydride elimination was observed in the attempted carbonnitrogen bond formation with a sterically bulky substrate (when R=tert-butyl).     

Alkylated trimethylene-bridged bis(p-phenylenediamines)

One and two electron oxidation of N,N',N',N'-tetramethyl-1,5,12,16-tetraaza[5,5]paracyclophane (Me3C), a bis-trimethylene bridged bis-p-phenylene diamine (PD), and its ethyl and isopropyl analogues are discussed. The monocation and dication are both stable, as demonstrated by optical studies that show they are in equilibrium in solution, with an especially small difference in first and second oxidation potentials for Me3C in MeCN (+23 to -20 mV, measured by simulation of the optical spectrum and of the cyclic voltammogram, respectively). The monocations have charge localized in one PD unit and show a Hush-type mixed valence transition between their PD0 and PD.+ groups. The dications Me3C2+ and Et3C2+ have optical spectra that appear to show large splittings between their PD.+ groups and have a weak ESR spectrum, and 1H NMR data show that the former is a ground-state singlet. iPr3C2+ has a very different optical spectrum and exhibits a triplet ESR spectrum at 120 K. X-ray crystal structures show that for Me3C0 the N(CH2)3N units on each side are in doubly anti (aa) conformations that put the aryl rings as far apart as possible, but Me3C2+ has doubly gg N(CH2)3N trimethylene bridges and both N,N and C,C distances between the PD.+ groups that are significantly below van der Walls contact. In contrast, iPr3C0 is in a doubly ag conformation, and its diradical dication is suggested to be a triplet because it does not attain the doubly gg conformation.     

Control of photochemical, photophysical, electrochemical, and photocatalytic properties of rhenium(I) complexes using intramolecular weak interactions between ligands

Intramolecular interactions between ligands have been successfully applied as a novel tool for controlling various properties of a series of cis,trans-[Re(dmb)(CO)(2)(PR(3))(PR'(3))](+)-type complexes (dmb = 4,4'-dimethyl-2,2'-bipyridine), in the ground state and in the excited state and in the one-electron reduced form. For rhenium complexes with two triarylphosphine ligands, P(p-XPh)(3), the dmb ligand was sandwiched by four aryl rings having CH(aryl)-pi(pyridine)-pi(aryl) interactions. On the other hand, complexes with one triarylphosphine ligand and one trialkylphosphite ligand, P(OR)(3), had pi-pi and CH-pi interactions between each pyridine ring in the dmb ligand and the aryl group in the P(p-XPh)(3). Various properties of these two series of rhenium complexes were compared with those of complexes having two trialkylphosphite ligands, which do not interact through space with the dmb ligand. Properties of the complexes associated mainly with the dmb ligand are strongly affected by the intramolecular interactions: (1) UV/vis absorptions to the pi-pi and (1)MLCT excited states were both red-shifted, but (2) emission from the (3)MLCT excited state was blue-shifted; (3) the lifetime of the (3)MLCT excited state was prolonged up to 3-fold; (4) the reduction potential in the ground state was positively shifted by 110 mV with pi-pi and CH-pi interactions and by 180-200 mV with the CH-pi-pi interactions. (5) In the excited states, the oxidation power of the complex was also enhanced by the intramolecular interactions. (6) In the corresponding one-electron-reduced species cis,trans-[Re(dmb(-.)(CO)(2)(PR(3))(PR'(3))], the intramolecular interactions are maintained and strongly affected their UV/vis spectra. (7) Photocatalysis for CO(2) reduction was significantly enhanced only by the CH-pi-pi interaction.     

threo‐2‐(2,6‐Dimethoxy­phen­oxy)‐1‐(4‐hydr­oxy‐3,5‐dimethoxy­phenyl)­propane‐1,3‐diol: a conformational study

In the crystal structure of the title compound, C₁₉H₂₄O₈, the mol­ecules adopt a conformation in which the bulky 2,6‐dimethoxy­phen­oxy and 4‐hydr­oxy‐3,5‐dimethoxy­phen­yl groups are almost as far apart as possible. The C(aryl)·C(aryl) distance is 4.8766 (19) Å, which is close to the calculated maximum value (4.92 Å). The C(aryl)—C—C—O(aryloxy) torsion angle is 173.76 (11)° and the C(benzylic)—C—O—C(aryl) torsion angle is 149.09 (11)°. The conformation is compared with those of related lignin model compounds. The hydrogen‐bonding pattern is discussed in terms of graph‐set theory.     

One-pot two step synthesis of unsymmetrically substituted indenes from 3,4-diarylbutadiene sulfones

A new one-pot two step synthesis of unsymmetrically substituted indenes from available 3,4-diarylbutadiene sulfones involves SO₂ thermal extrusion followed by acid- catalyzed cyclization of the diene formed, the cyclization proceeding selectively at the more electron-rich aryl rings. The procedure is efficient for substrates bearing donor, acceptor, as well as bulky substituents.     

P(MeNCH2CH2)3N: a highly selective reagent for synthesizing trans-epoxides from aryl aldehydes

In contrast to its acyclic analogue P(NMe2)3 (1), which in benzene at room temperature reacts with two aryl aldehyde molecules bearing electron-withdrawing groups to give the corresponding diaryl epoxide as an isomeric mixture (trans/cis ratios: 72/28-51/49), P(MeNCH2CH2)3N (2a) under the same reaction conditions is found to be a highly selective reagent that provides epoxides with trans/cis ratios as high as 99/1. These reactions are faster with 2a, because its phosphorus atom is apparently more nucleophilic than that in 1. Thus, it is found that 2a more easily forms 1:1 and 1:2 adducts with one or two molecules of aldehyde, respectively. These adducts apparently are intermediates in the formation of the product epoxide and the corresponding phosphine oxides of 1 and 2a.