1H-, 31P- and 13C-NMR spectra of some 2-arylsulphonylamido-2-thiono-5-methyl-1,3,2-dioxaphospholanes

Some 2-arylsulphonylamido-2-thiono-5-methyl-1,3,2-dioxaphospholanes (1), containing two chiral centres, give NMR spectra in which splittings of the ¹H and ¹³C signals of the 5-methyl substituent and of the ³¹P signal indicate that they exist in an approximately 70:30% ratio of two racemic mixtures, Z and E respectively, diastereomeric to each other. These splittings were invariably observed for compounds 1a, containing a monosubstituted sulphonylamido group (Y = H) and various substituents at position 4′ of the aryl group, X = H, CH₃, OCH₃, F, CI and Br. The methylenic protons in position 4 of the phospholane ring are diastereotopic and therefore magnetically non-equivalent. Benzene-induced shifts were measured for the Z isomers of compounds 1a, X = H, F and for compound 1b, containing an N-disubstituted sulphonylamido group (Y = CH₃) and X = H; the tentative interpretation of these shifts places the more shielded diastereotopic methylene proton on the same side of the ring as the 5-methyl substituent. The H? P and H? H coupling constants indicate that the preferred conformation of the dioxaphospholane ring should be a ‘twisted envelopey’ shape with the 5-methyl substituent in the equatorial position.     

The Structure of 3-Phenyl-4-(N-Carbamyl-1,4,2-Oxathiazolimin-3-yl)Sydnone,C11H7N5O4S·0.8 CH2Cl2

The title compound (M_r = 373) crystalizes in the othorhombic space group P bna with a = 10.410(2), b = 11.658(4), c = 23.108(3) Å, V = 2804.4 Å Z = 8. The single crystal intensity data were collected using MoK∞ radiation (λ = 0.7093Å) at room temperature. The crystal and molecular structure was solved with the final agreement index R = 0.039 for 1046 observed reflections. The bond lengths N(1)- C(7) and C(7)-C(8) of the title compound are slightly longer than those of 3-substituted sydnone derivatives. This may be attributed to the steric effect arising from the interaction of the phenyl ring and the 4-substituent with the neighboring atoms of sydnone ring. Both the title compound and 4-acetyl-3-(p-tolyl)sydnone have smaller dihedral angles between the sydnone ring and the plane of the sp² orbital of the double bond of the 4-substituent and both have shorter C(7)-C(9) bond lengths than those of other similar sydnone derivatives.     

Rebek Imide Platforms as Model Systems for the Investigation of Weak Intermolecular Interactions

A Rebek imide receptor with an acetylene‐linked phenyl ring complexes 2,6‐di(isobutyramido)pyridine in (CDCl₂)₂ via triple H‐bonding and π–π‐stacking interactions, and the influence of para‐substituents on both rings was investigated by ¹H NMR binding titrations. When the phenyl ring was extended to biphenyl and the C(4)‐pyridine substituent varied, interaction energies increased in the order CH₃CH₂???phenyl<CH₃S???phenyl<phenyl???phenyl?N‐methylcarboxamide???phenyl, highlighting the energetic gain from π stacking on amide fragments. The predicted preference of amide–π stacking for an antiparallel alignment of the local dipoles could not be confirmed with the studied system. Different substituents were introduced in the para position of the phenyl ring and their interaction with bound 2,6‐di(isobutyramido)pyridine was investigated. Theoretical predictions that the mere introduction of a substituent has a stabilizing effect on π–π stacking, regardless of its electronic nature, were experimentally confirmed.     

13C NMR spectra of p- and m-substituted phenyl N-methyl- and phenyl N,N-dimethyl-carbamates

¹³C NMR spectra of p- and m-substituted phenyl N-methylcarbamates, phenyl N,N-dimethylcarbamates and p- and m-substituted phenyl propionates were recorded, and their para ¹³C SCS (substituent chemical shifts) were analysed by DSP (dual substituent parameters) and DSP-NLR (non-linear resonance) equations. It was found that the fixed substituent Y, ? OCONHCH₃, ? OCON(CH₃)₂ and ? OCOC₂H₅, were all mild in the sense that DSP analysis gave a good correlation, leaving little room for improvement by the DSP-NLR treatment. Further, the three series of compounds gave similar ρ_I and ρ_R values (para derivatives, 3.2–3.3 and 17.7–18.0; meta derivatives, 5.1–5.2 and 21.8–22.0). Examination of the corresponding analyses of similar compounds indicated that the ρ_I and ρ_R values and, hence, their ratio ρ_R/ρ_R = λ, depended primarily on the nature of the atom through which the fixed substituent Y (e.g. α-C, α-N and α-O) was bonded to the aromatic ring when the Y substituents are mild. The extent of this tendency for compounds with active fixed substituents is also discussed.     

Synthesis,properties and solid state structure of 5‐diphenylphosphino‐2‐hydroxy‐1,3‐xylyl‐18‐crown‐5

5‐Diphenylphosphino‐2‐hydroxy‐1,3‐xylyl‐18‐crown‐5 has been synthesized from 5‐bromo‐2‐hydroxy‐18‐crown‐5 by reacting it in sequence at low temperature with n‐butyl lithium and methyl diphenylphosphonite. The phosphorous donor properties of this phenol phosphine (OH derivative) and the corresponding phenoxide (O^? derivative) have been studied in the presence and absence of alkali metal ions by determining the frequencies of the A₁ ν(CO) bands of Ni(CO)₃L complexes. For the OH and O^? derivatives, the latter generated by addition of CsOH to the former, the ν(CO) bands are observed at 2067.6 and 2063.4 cm^?1, respectively, providing the trend predicted by Hammett parameters for OH and O^? substituents. Addition of Na⁺ or K⁺ to the OH derivative has little effect on this stretching frequency, but the former ion shifts the O^? derivative band to 2067.7 cm^?1 A solid state structure has been obtained of the OH derivative, and two independent molecules were found in the unit cell. Both have a single water molecule hydrogen bonded to two across‐ring oxygen atoms and the phenol hydrogen. The crown ether ring has the usual gauche and anti arrangements for the C‐C and C? O bonds.     

Three isomeric forms of hydroxyphenyl‐2‐oxazoline: 2‐(2‐hydroxyphenyl)‐2‐oxazoline, 2‐(3‐hydroxyphenyl)‐2‐oxazoline and 2‐(4‐hydroxyphenyl)‐2‐oxazoline

Crystal structures are reported for three isomeric compounds, namely 2‐(2‐hydroxy­phenyl)‐2‐oxazoline, (I), 2‐(3‐hydroxy­phenyl)‐2‐oxazoline, (II), and 2‐(4‐hydroxy­phenyl)‐2‐oxazoline, (III), all C₉H₉NO₂ [systematic names: 2‐(4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenol, (I), 3‐(4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenol, (II), and 4‐(4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenol, (III)]. In these compounds, the deviation from coplanarity of the oxazoline and benzene rings is dependent on the position of the hydroxy group on the benzene ring. The coplanar arrangement in (I) is stabilized by a strong intra­molecular O—H⋯N hydrogen bond. Surprisingly, the 2‐oxazoline ring in mol­ecule B of (II) adopts a ³T₄ (^C2T_C3) conformation, while the 2‐oxazoline ring in mol­ecule A, as well as that in (I) and (III), is nearly planar, as expected. Tetra­mers of mol­ecules of (II) are formed and they are bound together via weak C—H⋯N hydrogen bonds. In (III), strong inter­molecular O—H⋯N hydrogen bonds and weak intra­molecular C—H⋯O hydrogen bonds lead to the formation of an infinite chain of mol­ecules perpendicular to the b direction. This paper also reports a theoretical investigation of hydrogen bonds, based on density functional theory (DFT) employing periodic boundary conditions.     

Protonenresonanzuntersuchungen an Aminoboranen—II: Einflüsse von para-Phenylsubstituenten auf die Rotationsbarriere um die N?B-Bindung

The electronic influence of substituents on the free enthalpy of rotation around the N? B bond in aminoboranes was investigated in two series of compounds: (a) (CH₃)₂N?BCl (phenyl-p-X), containing the para-phenyl substituent at the boron atom, and (b) (p-X-phenyl)CH₃N?B(CH₃)₂, containing the para-phenyl substituent at the nitrogen atom of the N? B linkage (X = ? NR₂, ? OCH₃, ? C(CH₃)₃, ? Si(CH₃)₃, ? H, ? F, ? Cl, ? Br, ? I, ? CF₃ and ? NO₂). By comparing the rotational barriers in corresponding compounds of both series, a reverse effect of the substituents could be observed. Electron-withdrawing substituents in the para position of the phenyl ring increase the ΔG_c^≠ if the phenyl group is attached to the boron atom; on the other hand, a lower ΔG_c^≠ is observed if the phenyl ring is bonded to the nitrogen atom of the N? B system. Substitution of the phenyl ring with electron-donating substituents in the paraposition exerts the opposite effect. Within each series of compounds, the differences of ΔG_c^≠ values [δ(ΔG_c^≠) = ΔG_c^≠ (X) ? ΔG_c^≠ (X = H)] between substituted and unsubstituted compounds can be explained in terms of inductive and mesomeric effects of the ring substituents and can be correlated with the Hammett σ constant of each substituent. A comparison of the slopes of the plotted lines shows that the influence of the ring substituents is more pronounced in compounds with N-phenyl-p-X than in those with B-phenyl-p-X.     

Excited state intramolecular proton transfer (ESIPT) from phenol OH (OD) to adjacent “aromatic” carbons in simple biphenyls

This work reports results of further studies on a new class of excited state intramolecular proton transfer (ESIPT), from phenol OH to adjacent aromatic carbon atoms of suitably designed biphenyl systems. For this purpose, a number of 2-phenylphenols 3–6 with methyl and methoxy substituents on the adjacent proton accepting phenyl ring were synthesized. In particular, we were also interested in studying the effect of an acetyl (ketone) substituent on the proton accepting ring (biphenyl 7) and the effect on the photochemistry when the ketone is reduced to alcohol (biphenyl 8). All compounds except for 7 were found to undergo deuterium exchange (Ф_ex = 0.019–0.079) primarily at the 2′-position on photolysis in 1:3 D₂O–CH₃CN. This is consistent with a reaction mechanism involving initial ESIPT from the phenol OH to the 2′-position of the adjacent phenyl ring, to generate a biphenyl quinone methide intermediate which rapidly tautomerizes back to starting material. Biphenyl 8 also undergoes a competing photosolvolysis reaction (overall loss of water). Both photosolvolysis and ESIPT reactions react via isomeric quinone methide intermediates and are best interpreted as arising from an excited singlet state that possesses a large degree of charge transfer character, from the phenol ring to the attached phenyl ring. The failure of 7 to react may be due to two possible reasons: (i) high intersystem crossing rate to a non-polarized triplet excited state and/or (ii) a polarized singlet state that is now much more basic at the carbonyl oxygen. The results are consistent with qualitative examination of calculated HOMOs and LUMOs (AM1).     

Radical Copolymerization of Vinylidene Chloride with 3(2-Methyl)-6-methylpyridazinone in Several Solvents

The radical copolymerization of vinylidene chloride (Vc, M₁) with 3(2-methyl)-6-methylpyridazinone (I, M₂) was carried out in benzene, ethanol, phenol, and acetic acid at 60 and 80°C. The monomer reactivity ratios were found to vary with the reaction conditions. The linear correlationships were obtained by plotting the values of log r₁ against those of ^V C[dbnd]O and ^V C[dbnd]C of monomers determined in the solvents.     

Alternating copolymerization of methyl acrylate with donor monomers having a protected amine group

Attempts were made to copolymerize p-aminostyrene, p-acetamidostyrene, N-methyl-p-aceta-midostyrene, N-(4-vinylphenyl) phthalimide, N-vinyl succinimide, and N-vinyl phthalimide with methyl acrylate complexed with ethyl aluminum sesquichloride. Only reactions involving N-(4-vinylphenyl)phthalimide and N-vinyl phthalimide yielded alternating copolymers. N-vinyl succinimide gave nonalternating copolymers insoluble in common solvents and the other monomers did not copolymerize. In some cases, the conventional radical copolymers were prepared for comparison purposes. The reactivity ratios of the free-radical initiated copolymerization of methyl acrylate (I) with N-(4-vinylphenyl)phthalimide (II) were r₁ = 0.14 and r₂ 1.56. The alternating copolymers were studied by ¹H-NMR and ¹³C-NMR spectroscopy. The alternating copolymer of N-(4-vinylphenyl)phthalimide with methyl acrylate was hydrazinolyzed to form the alternating copolymer of methyl acrylate with p-aminostyrene. Hydrazinolysis of the alternating copolymer of methyl acrylate with N-vinyl phthalimide removed the phthalimide moiety and generated vinyl amine units which readily cyclized with neighboring methyl acrylate units to form copolymers that contained five-membered lactam rings. The infrared (IR) spectra of the hydrazinolyzed products contain bands due to amine or amide groups and are devoid of the characteristic bands of the phthalimide ring.     

Nitrogen Bridgehead Compounds. Part 81. Synthesis of 9-(benzylidenehydrazono)-6-methyl-4-oxo-6,7,8,9-tetrahydro- and 9-(benzylidenehydrazine)-6-methyl-4-oxo-6,7-dihydro-4H-pyrido[1,2-a]-pyrimidine-3-carboxylates

Reaction of ethyl 9-hydrazono-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylate and benzaldehyde and its derivatives give a tautomeric mixture of 9-arylidenehydrazono-6,7,8,9-tetrahydro- and 9-arylidenehydrazine-6,7-dihydropyrido[1,2-a]pyrimidine derivatives. In the same case the enhydrazine and hydrazone tautomers were separated. The structure of the products were characterised by uv, ir, ¹H and ¹³C nmr. The equilibrium of the tautomers was affected by the substituent of the phenyl ring. A fair linear correlation exists between the logarithms of the equilibrium constants and Hammett σ_m and σ^? constants of the substituents present on the phenyl ring.     

Conformational mobility of the six-membered ring in 5-oxo-1,3-cyclohexadiene and its derivatives

Molecular mechanics and MNDO calculations showed that the six-membered ring in the molecule of 5-oxo-1,3-cyclohexadiene possesses high conformational mobility. The transition from a planar equilibrium conformation to a distorted sofa conformation in which the C(sp²)-C(=O)-C(sp³)-C(sp²) torsion angle is equal to ±30° increases the energy of the molecule by less than 1 kcal mol^–1. The influence of steric (R = Me, Et, Prⁱ, Bu^t) and electronic (R = NH₂, NO₂) effects of substituents R on the equilibrium conformation and mobility of the carbocycle has been analyzed. Both types of substituents at unsaturated C atoms do not change the equlibrium conformation or flexibility of the six-membered ring. Substituents at saturated C atoms cause the transition of the carbocycle to the distorted sofa conformation and significantly restrict its mobility. The electronic structures of 5-oxo-1,3-cyclohexadiene and its amino and nitro derivatives have been analyzed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 849–854, May, 1995.     

New unsymmetrical μ-phenoxo bridged binuclear copper(II) complexes

A series of binuclear Cu^II complexes [Cu₂XL] ⁿ⁺ having two copper(II) ions bridged by different motifs (X = OH^–, MeCO₂ ^–, or Cl^–) have been prepared using the ligands: H₂L¹ = 4-methyl-2-[N-(2-{dimethylamino}ethyl-N-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H₂L² = 4-nitro-2-[N-(2-{dimethylamino}ethyl-N-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H₂L³ = 4-methyl-2-[N-(2-{diethylamino}ethyl-N-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol and H₂L⁴ = 4-nitro-2-[N-(2-{diethylamino}ethyl-N-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol. The complexes have been characterized by spectroscopic, analytical, magnetic and electrochemical measurements. Cryomagnetic investigations (80–300 K) revealed anti-ferromagnetic exchange between the Cu^II ions (–2J in the range –50 to –182 cm^–1). The strength of anti-ferromagnetic coupling lies in the order: OAc > OH > Cl. Cyclic voltammetry revealed the presence of two redox couples, assigned to Cu^II/Cu^II/Cu^II/Cu^I/Cu^I/Cu^I. The first reduction potential is sensitive to electronic effects from the aromatic ring substituents and steric effect on the donor nitrogens (side arm) of the ligand systems.     

Interactions intramoléculaires—XIX: Constantes de couplage vicinales, équilibres conformationnels et interactions gauches (séries cyclohexanique et cyclohexénique)

NMR parameters are determined and identified for the four stereoisomers of 3,4-dimethyl methoxycarbonylcyclohexane (d₃-2,2,3,4,5,5), the two stereoisomers of 2-methyl methoxycarbonylcyclohexane (d₅-2,3,4,5,5) and 3-methyl 4-X cyclohexene (d₃-3,6,6) (X = COOCH₃, CH₂OH, CH₂Cl). For the axial COOCH₃ substituted cyclohexane, the vicinal coupling constants are in agreement with the ring deformation. Different conformational equilibria are estimated and discussed, especially in relation to the inequality of gauche interactions between two cis vicinal substituents.     

The psuedo‐michael reaction of 2‐aminoimidazolines 2. Part 1. Synthesis and structure assignment of isomeric 5(1H)‐Oxo and 7(1H)‐Oxo‐2,3‐dihydroimidazo[1,2‐a]pyrimidine‐6‐carboxylates

The pseudo‐Michael reaction of 1‐aryl‐2‐aminoimidazolines‐2 with diethyl ethoxymethylenemalonate (DEEM) was investigated. Extensive structural studies were performed to confirm the reaction course. For derivatives with N1 aromatic substituents, it was found that the reaction course was temperature dependent. When the reaction temperature was held at ?10 °C only the formation of 1‐aryl‐7(1H)‐oxo‐2,3‐dihydroimi‐dazo[1,2‐a]pyrimidine‐6‐carboxylates ( 4 ) was observed in contrast to earlier suggestions. Under the room temperature conditions, the same reaction yielded mixtures, with varying ratio, of isomeric 1‐aryl‐7(1H)‐oxo‐ ( 4a‐4f ) and 1‐aryl‐5(1H)‐oxo‐2,3‐dihydroimidazo[1,2‐a]pyrimidine‐6‐carboxylates ( 5a‐5f ). The molecular structure of selected isomers, 4b and 5c , was confirmed by X‐ray crystallography. Frontal chro‐matography with delivery from the edge was applied for the separation of the isomeric esters. The isomer ratio of the reaction products depended on the character of the substituents on the phenyl ring. The 1‐aryl‐7(1H)‐oxo‐carboxylates ( 4a‐4f ) were preferably when the phenyl ring contained H, 4‐CH₃, 4‐OCH₃ and 3,4‐Cl₂ substituents. Chloro substitution at either position 3 or 4 in the phenyl ring favored the formation of isomers 5a‐5f . The isomer ratios were confirmed both by ¹H NMR and chromatography. The reaction of the respective hydrobromides of 1‐aryl‐2‐aminoimidazoline‐2 with DEEM, in the presence of triethylamine, gave selectively 5(1H)‐oxo‐esters ( 5a‐5f ).     

BIOLOGICALLY DERIVED PHOTOACTIVE MACROMOLECULAR AZODYES

Azophenols with various substituents at the para position of the phenyl ring were enzymatically polymerized in the presence of H₂O₂. Structural characterization of the synthesized polymers by FTIR, FT-Raman, and NMR (¹H and ¹³C) spectroscopy confirms our previous observation that this enzymatically catalyzed coupling reaction occurs primarily at the ortho positions, with some substitution at the meta position of the phenol ring. The strong constraint and poor packing of the azobenzene chromophores in the polymer leads to a significant blue shift of the π-π^* transition absorption and slow photoisomerization and thermal relaxation in comparison to the monomers. Surface relief gratings (SRG) with large surface modulation have been fabricated on these enzymatically synthesized polymer films.

     

Determination of vinyl orientation of mouse neuroglobin by 2D nuclear Overhauser spectroscopy

1H NMR has been used to determine the 2-,4-vinyl orientation of heme active site from oxidized mouse neuroglobin (mNgb).The NOEs between 3-methyl and Hα, Hβ of 2-vinyl, together with the NOEs between 5-methyl and Hα, Hβ of 4-vinyl, allowed the unambiguous determination of trans and cis orientations for the 2- and 4-vinyl groups in the mNgb, respectively.     

Novel Copolymers of Styrene. 1. Alkyl Ring-Substituted Butyl 2-Cyano-3-Phenyl-2-Propenoates

Novel trisubstituted ethylenes, alkyl ring-substituted butyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO₂C₄H₉ (where R is 2-methyl, 3-methyl, 4-methyl, 2-ethyl, 4-ethyl, 4-butyl, 4-t-butyl, 4-i-butyl) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and butyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r₁) for the monomers is 4-ethyl (4.69) > 3-methyl (4.18) > 4-t-butyl (2.98) > 2-ethyl (2.52) > 4-butyl (2.47) > 4-methyl (1.86) > 4-i-butyl (0.94) > 2-methyl (0.87). Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (3–8% wt), which then decomposed in the 500–800°C range.     

Proton NMR studies of reduced porphyrin compounds

Detailed ¹H NMR studies of ms tetraphenylchlorins (H₂TPC), new amino- and hydroxypyrroline substituted ms tetraphenylchlorins and ms tetraphenylisobacteriochlorins (H₂TPisoB) are presented and discussed. The results obtained are consistent with the general aspects of the ring current models as applied to the parent porphyrins. According to proton chemical shifts a gradual reduction in the magnitude of the ring current is observed in the order ms tetraphenylporphyrin (H₂TPP) > H₂TPC> ms tetraphenylbacteriochlorin (H₂TPB) > H₂TPisoB. The ¹H NMR spectra show chemical non-equivalence of the pyrroline ring protons due to adjacent substituents, and effects of steric constraints on the aminoalkyl substituents due to the close vicinity to the meso phenyl rings. The non-equivalence of the methylene protons of the pyrroline ring produces geminal coupling between the two methylene protons and vicinal coupling with the adjacent pyrroline proton, more pronounced in H₂TPC? OH and in . Restricted configuration of the methylene groups in the ethyl groups of H₂TPC? C(H)(CH₃)N(CH₂CH₃)₂ produces observable geminal coupling between the methylene protons. ¹H NMR reveals the difference between two types of meso phenyls in the chlorins, and three types of meso phenyls in isobacteriochlorins, as reflected in the chemical shifts of the o-phenyl protons.