1H NMR spectra of 1-alkyl-1,2,3,4-tetrahydro-2-oxo-3-azocine-carboxylic acid derivatives and their analogues

¹H NMR spectra of 1-alkyl-1,2,3,4-tetrahydro-2-oxo-3-azocinecarboxylates and -carbonitriles indicated that the geminal protons at the 1-α-position were located in noneqnivalent magnetic environments. The difference in the chemical shifts amounted to as much as 0.73 ppm in the case of methyl 1-ethyl-1,2,3,4-tetrahydro-2-oxo-3-azocinecarboxylate at 26°, and the free energy of activation for the coalescence was estimated to be larger than 23 $\text{kcal}\text{mol}$. The same type of nonequivalence and coalescence phenomena were also observed even with dimethyl protons at the 1-γ-position of 1-isobutyl-1,2,3,4-tetrahydro-2-oxo-3-azocinecarboxylate (ΔG^≠_c = 19 $\text{kcal}\text{mol}$). The situation was hardly affected by the reduction of the CC double bonds. The nonequivalence was not observed, however, if the substituent at the 3-position was absent. Therefore, these novel ¹H NMR spectra of 1-alkyl protons in the title compounds were concluded to be due to strong coupling between the restricted rotation around N(1)—C(α) bond and inversion of the 2-oxoazocine ring which required high energy of activation.     

The conformation of 4-t-butylcycloheptanone

The 400 MHz ¹H NMR spectra of two deuterated derivatives of 4-t-butylcycloheptanone ($\text{2}$ and $\text{3}$) provided ²J_HH values for the α-methylene protons on each side of the carbonyl group. The interpretation of their magnitude shows clearly that the carbonyl group is located at position 1 of the twist-chair conformation while the t-butyl group is located at position 4e.     

Proton and carbon nuclear magnetic resonance study on some n- and o-acyl derivatives of monohydroxypyridines

Comparative study on the proton and carbon NMR spectra for a series of $\text{N}$- and $\text{O}$-acyl substituted monohydroxypyridines (C₅H₄NO$\text{R}$: $\text{R}$=-H, -CHO, -COCH₃, -COC(CH₃)₃, -COCF₃, -COC₆H₅, -SO₂CH₃, -SO₂C₆H₄CH₃ is reported. p]Characteristic ¹H, ¹³ NMR and IR spectral features allow simple and unambiguous distinction between the isomeric $\text{N}$- and/or $\text{O}$-acyl-derivatives of 2-, 3- and 4-hydroxypyridines, so that both forms can clearly be identified when tautomeric equilibria occur, since the tautomerism rate is slow on the NMR time scale     

Action of tert-butyl azidoformate on the conjugate bases of 1,2,3,4-tetrahydro-9H-carbazole and other indole derivatives

tert-Butyl azidoformate ($\text{2}$) reacts with the conjugate bases of $\text{3a}$, $\text{7a}$, $\text{9}$ (R¹ = R² = CH₃), and $\text{9}$ (R¹ = CH₃, R² = H) to give products [$\text{4}$, $\text{8}$, $\text{12}$, and $\text{14}$, respectively] in addition to the expected N-(tert-butoxycarbonyl)indole derivatives.     

O- versus N-methanesulphonylation and N-(methanesulphonyl)-methanesulphonylation with methanesulphonyl chloride

Depending upon the experimental conditions, t-butyl (1$\text{SR}$,5$\text{SR}$,7$\text{RS}$,8$\text{RS}$)-1-ethoxycarbonyl-8-hydroxy-2-oxa-6-azabicyclo[3.2.0]octane-7-carboxylate (2a) reacts with methanesulphonyl chloride to give predominantly the $\text{O}$-methanesulphonyl derivative (2b), the $\text{N}$-methanesulphonyl derivative (3a), or the $\text{N}$-(methanesulphonyl)methane-sulphonyl derivative (6a).     

Comparison of steric effects on 31P chemical shifts in some 7-norbornyl, 7-norbornenyl and cyclohexyl phosphorus compounds

Phosphorus-31 NMR spectra were obtained on both syn and anti isomers of norbornenes with the 7-position bearing Cl₂P-, Me₂P-, Me₂(S)P- and Me₃P as substituents. Norbornanes with 7-Cl₂P- and 7-Me₂P- were also studied. Just as is true for ¹³C shifts for 7-Me in these bicyclo[2.2.1]heptane derivatives, the ³¹P shifts all fall noticeably upfield of published values for comparable cyclohexane derivatives. Consistent also with the ¹³C effect, a slight shielding of ³¹P in Me₂P- (1.1 ppm) was noted when this group was syn to the double bond of the norbornene system, relative to the value for the anti compound, suggesting the sensitivity of ³¹P to a diamagnetic effect from the double bond. However, the more space-demanding Cl₂P group when moved from the crowded anti to the less crowded syn position experienced a strong deshielding effect, as did the Me₂(S)P- and Me₃P- groups. The opposite is seen when these same groups are moved from the crowded axial to the less crowded equatorial position of cyclohexane, and a new structural influence appears to be operating in this system. A recent proposal that steric compression causes bond angles about phosphorus to increase and that this is the cause of the γ-shielding effect is not supported by published NMR and X-ray structural data for cis- and trans-1-methyl-4-tert-butyl-4-phosphorinanol. Bond angles about phosphorus are virtually identical in these isomers, yet ³¹P shifts differ by 6.9 ppm.     

A facile formation of cyclic selenuranes and a cyclic selenurane oxide in the reaction of 2-methylseleno- and 2-phenylselenobenzoic acids and their derivatives with t-butyl hydroperoxide

The reaction of 2-methylselenobenzoic acid with 1,1′-carbonyldiimidazole followed by addition of t-butyl hydroperoxide gave cyclic selenuranes $\text{2a}$ and $\text{3a}$, suggesting the intramolecular insertion of the neighboring selenium atom into the OO bond of t-butyl 2-methylselenoperoxybenzoate. In the reaction of 2-phenylselenobenzoyl chloride with t-butyl hydroperoxide, cyclic selenurane $\text{2b}$ and the oxide $\text{7}$ were obtained.     

Conformational equilibria in halocyclohexanones,an NMR and solvation study

The conformational equilibrium in 2-chloro cyclohexanone is measured in thirteen solvents from the 220 MHz¹H NMR spectrum using the C₂-H couplings and chemical shifts and the cis and trans 4-t-butyl-2-chlorocyclohexanones as reference compounds. ΔG_ea varies from 1.04 $\text{kcal}\text{mole}$ in n-pentane to ?0.58 $\text{kcal}\text{mole}$ in DMSO. The large concentration dependence of the NMR parameters in non-polar solvents noted previously is confirmed.Generalised reaction-field theory is used to calculate this solvent dependence, using a refined model of the geometry and dipole moments of the conformers.The cyclohexanone ring is considerably flatter than that of cyclohexane and this has an appreciable effect on the resultant dipole moments. Use of this geometry and CO and C-Cl bond moments which reproduce the observed dipole moments of the t-butyl compounds together with the generalised reaction field theory gives calculated solvation energies in good agreement with the observed data and hence allows the prediction of the vapour state energy difference.The model is applied to a variety of halo-ketones and gives both a reasonable explanation of the observed solvent dependencies and also the vapour state energy differences.The vapour state conformer energies are compared with the corresponding values for the halocyclohexanes and illustrate the large polar and steric effects due to the introduction of the CO group.     

Stereocontrolled synthesis of 7-hydroxy- and 7-acetoxy-PGI2: New stable PGI2 analogues

Stable analogues of PGI₂, 7-hydroxy- and 7-acetoxy-PGI₂, were synthesized from protected PGI₂ methyl ester $\text{1b}$via sulfoxides $\text{6a}$, $\text{6b}$ through stereocontrolled sulfoxide-sulfenate rearrangement.     

Organothallium compounds XII NMR spectra of some polyfluorophenylthallium (III) compounds

The PMR and ¹⁹F NMR spectra of the complexes R₂TlBr (R = C₆F₅, $\text{o}$-HC₆F₄, $\text{m}$-HC₆F₄, 3,5-H₂C₆F₃, or 3,6-H₂C₆F₃ and R₃Tl(diox) (R = C₆F₅, $\text{m}$-HC₆F₄, or 3,5-H₂C₆F₃; diox = 1,4-dioxan) have been recorded. Proton and fluorine chemical shifts, thallium-proton, thallium-fluorine, fluorine-fluorine, and fluorine-proton coupling constants, and thallium substituent chemical shifts are given and discussed     

K4Au7Ge2: eine Gerüststruktur mit Au7-Doppeltetraedern und Ge2-Hanteln

K₄Au₇Ge₂: a Framework Structure with Au₇-Double-Tetrahedra and Ge₂-Dumb-Bells Black lustrous, brittle single crystals of a hitherto unknown K₄Au₇Ge₂ were synthesized by the reaction of KN₃, germanium- and gold-powder at 550°C. The structure was determined from X-ray single-crystal diffractometry data: space group R3 m, Z = 3, a = 6.411(3) Å, c = 27.912(20) Å, R/R_w(w = 1) = 0.046/0.056, Z(F ${}_{\text{º}}^{\text{2}}$ ) ≥ 3σ(F ${}_{\text{º}}^{\text{2}}$ ) = 302 and N(var.) = 18. K₄Au₇Ge₂ crystallizes in a substitution variant of the MgCu₂-type. Gold and germanium form a framework structure that consists of corner-sharing Au₇-double-tetrahedra and Ge₂-dumb-bells. The potassium atoms occupy channel-like cavities within the gold germanium partial structure.     

1,1-Diaminosubstituted 2-azaallenium salts: preparation and barriers to topomerization

Dialkylcarbodiimides, $\text{5}$, react with iminium salts, $\text{6}$, to afford the formal 1,1-diaminosubstituted 2-azaallenium salts $\text{3}$. According to dynamic NMR measurements compounds $\text{3}$ must be regarded as alkylidene-guanidinium salts $\text{A}$, undergoing a fast topomerization via a transition state $\text{B}$ with allene geometry (2G⁼₂₆₅ = 45.9 ± 1 kJmol^-1 for $\text{3f}$) and a slower rotation around the peripheral C-N bonds (transition state $\text{C}$; 2G⁼₂₉₀⁼ 58.0 ± 1 kJmol^-1 for $\text{3f}$).     

Conformational dependence of pyranoid rings 1,2-cis-fused to dioxolane rings on the configuration of the dioxolane rings in acetylated derivati

X-Ray and ¹H N.M.R. studies on pyranoid rings 1,2-$\text{cis}$-fused to dioxolane rings in acetylated $\text{D}$-gluco- and $\text{D}$--galactopyranose derivatives demonstrate that the configuration of the dioxolane ring influences the conformation of the pyranoid ring in the $\text{D}$-gluco but not in the $\text{D}$-galactopyranose series. The crystal structure of 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-(R)--(l-cyano-ethylidene)-α-$\text{D}$-glucopyranose ($\text{1}$) and 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-($\text{R}$)-(1-cyano-ethylidene)-α-$\text{D}$-galactopyranose ($\text{2}$)have been determined by X-ray analysis. Lattice parameters for $\text{1}$ are a=20.6021 (11), b=8.0438 (2), c=5.5541 (1) Å and β= 95.588 (3)° for a cell with P21 symmetry. These parameters for $\text{2}$ are a=20.3361 (7), b=10.0907 (2), c=18.9115 (5) Å, β =112.399 (2)°, C2, with two crystallographycally independent molecules. The conformation of the pyranoid ring in both compounds can be described as flattened ⁴C₁ and that of the dioxolane ring as distorted E₁. The importance of the torsion angles for describing problems of configuration is remarked and the use of relative configurational angles is stressed. The ¹H N.M.R. spectra of $\text{1}$ and $\text{2}$ and 3,4,6-tri-$\text{O}$-acetyl-1,2-O-(S)- and (R)-ethylidene-α-$\text{D}$-glucopyranose ($\text{5}$ and $\text{7}$), 3,4,6-tri-O-acetyl--1,2-O-(S)- and ($\text{R}$)-ethylidene-α-$\text{D}$-galactopyranose ($\text{6}$ and $\text{8}$), and 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-($\text{S}$)-and ($\text{R}$)-benzylidene-α-$\text{D}$-glucopyranose ($\text{9}$ and $\text{10}$) have been analyzed by using iterative computer methods and N.O.E. measurements. The results indicate that the major solution conformation of the pyranoid ring of the derivatives in the $\text{D}$-gluco series $\text{1}$, $\text{5}$ and $\text{9}$ may be described as flattened ⁴C₁ and that of $\text{7}$ and $\text{10}$ as ²$\text{S}$₅. The major solution conformation of the pyranoid ring in all compounds in the $\text{D}$-galacto series ($\text{2}$,$\text{4}$,$\text{6}$,$\text{8}$) may be described as flattened ⁴$\text{C}$₁.     

Preparation,crystal and molecular structure of,and NMR parameters for,the exopolyhedral heterocyclic platinaundecaborane [μ-2,7-(SCSNEt2)-7-(PMe2Ph)-NIDO-7-PtB10H11]

The compound [μ-2,7-(SCSNEt₂)-7-(PMe₂Ph)-nido-7-PtB₁₀H₁₁] has been obtained in a yield of 52% from the reaction of [7,7-(PMe₂Ph)-nido-7-PtB₁₀H₁₂] and [AuBr₂(S₂CNEt₂)], and identified by single crystal X-ray diffraction analysis and multi-element single and double resonance NMR spectroscopy. The yellow-orange compound crystallizes in the monoclinic space group P2₁/n with a 1179.2(2), b = 1244.9(5), c = 1641.4(2) pm, β = 95.45(1)°, Z = 4, and the structure (R 0.0209, R_w = 0.0211 for 3719 observed reflections) is that of a nido-7-platinaundecaborane with an exopolyhedral N,N-diethyldithiocarbamate ligand bridging the Pt(7) and B(2) positions to give a $\text{-Pt-B-C-S-}$ five-membered ring. The tetrahapto platinum-to-borane bonding has a considerable twist distortion relative to other nido-7-platinaundecaboranes which do not possess this cyclic feature. The NMR parameters exhibit no anomalies and are consistent with the crystal molecular structure. A plot of δ(¹¹B) vs δ(¹H) for directly bound exo-terminal hydrogen atoms shows good correlation with the slope 16 : 1.     

Studies on the reaction of 1,2-dicarbonyl compounds with dimethyl 3-ketoglutarate. Steric and electronic effects

The steric and electronic influences of substituents attached to the 1,2-dicarbonyl system on the success of the reaction of 1,2- diketones with dimethyl 3-ketoglutarate $\text{2}$ have been examined. It is clear from the reaction of $\text{2}$ with benzil, thienil, furil, and phenanthrenequinone $\text{5}$, respectively, coupled with ¹³C NMR spectroscopy of the reaction intermediates, that steric effects play a major role in the overall success of the reaction to provide $\text{4}$. This is analogous to the situation observed earlier with 1,2-diketones, R-CO-CO-R, where R represented an aliptiatic or alicyclic group.     

Peptides containing β-turns I-- cyclo-(gly-l-cys-gly)3 triply bridged by 1,3,5-tris-(thiomethyl)benzene

Reaction of $\text{cyclo}$-(Gly-$\text{L}$-Cys-Gly)₃ with 1,3,5-$\text{tris}$-bromomethylbenzene yields a $\text{tris}$ thioether of the cyclic nonapeptide in 28% yield. Both ¹H and ¹³C NMR spectra are consistent with a molecule of 3-fold symmetry; the temperature dependences of chemical shifts of the amide hydrogens are consistent with a structure composed of three β-turns.     

Cyclisatioh de diarylalcanes en milieu superacide : synthese de cetones tricycliques a methyle angulaire et mecanisme de leur isomerisation

Cyclisation of readily available diary1-1,2 ethanes $\text{1→4}$ proceeds in SbF₅,-HF at 0°C to yield tricyclic phenanthrenones $\text{5}$, $\text{6}$, $\text{7}$ and $\text{11}$ bearing an angular methyl group. This process implies the electrophilic attack of the more basic aromatic ring, reacting through its diprotonated form (on the oxygen and the meta carbon atom) on the second aromatic ring. Isomerization of these primary products may be observed to give ketones $\text{8}$, $\text{9}$, $\text{10}$ from $\text{3}$ and $\text{12}$ from $\text{4}$) and it has been demonstrated by the use of specifically deuterated $\text{3d}$ that it involves stereospecific 1,2 hydride (or deuteride) shifts, without exchange.     

The preperation and coordination properties of 1,4-diaza-3-methylbutadiene-2-ylpalladium(II) complexes with different substituents on the imino nitrogen atoms

The complexes trans-[PdCl{$\text{C(=NR)C}$(ME)=NR'} (PPh₃)₂] (R=C₆H₁₁,p-C₆H₄OMe; R$\text{.}\text{?}$=p-C₆H₄OMe, Me) containing a σ-bonded 1,4-diaza-3-menthyl-butadiene-2-yl group with different substituents on the nitrogen atoms have been prepared by two routes. The first involves initial methylation of the mixed isonitrile complex [PdCl₂(CNR)(CNR')]by HgMe₂, followed by reaction with PPh₃ ($\text{Pd}\text{PPh}{}_3$molar ratio $\text{1}\text{2}$). The second method involves condensation of primary aliphatic amines with the carbonyl group of the 1-azabut-1-en-3-one-2-yl moiety of the complex trans-[PdCl{$\text{C(=NR)C}$(Me) = 0} (PPh₃)₂]. The 1,4-diaza-3-methylbutadiene-2-yl derivatives act through their imino nitrogen atoms as chelating ligands towards anhydrous metal chlorides MCl₂ (M = Co, Ni, Cu, Zn). Magnetic moment measurements and the far-infrared and electronic spectra of these adducts indicate an essentially pseudo-tetrahedral configuration at M in the solid and in solution. With the ZnCl₂ adducts, the ¹H NMR pattern for the phenyl protons of the p-methoxyphenyl N-substituents dependss upon the position of the substituent i the 1,4-diazabutadiene chain.     

Optisch aktive übergangsmetall-komplexe : XVIII. Über die reaktion von C5H5Co(CO)(C3F7)j mit isonitrilen

In the reaction of C₅H₅Co(CO)(C₃F₇)I with isonitriles in the molár ratio $\text{1}\text{1}$ the brown complexes C₅H₅Co(CNR)(C₃F₇)I are formed. The fluorine atoms of the α-CF₂ groups are diastereotopic because of the asymmetric center at the Co atom. With (—)-α-phenylethylisonitrile a pair of diastereoisomers is obtained which could not be separated.C₅H₅Co(CO)(C₃F₇)I and C₅H₅Co(CNR)(C₃F₇)I react with excess isonitrile with the formation of benzene soluble, yellow salts [C₅H₅Co(CNR)₂(C₃F₇)]⁺I^?, which can be transformed into the corresponding PF^?₆ salts. The new compounds were characterised by C, H, N, Co analyses, molecular weight determinations, IR, ¹H NMR, ¹⁹F NMR, ¹³C NMR, ESCA and mass spectra.     

X-ray molecular structure of the 1:1 adduct of [FeH(CO)4]− and dimethyl acetylenedicarboxylate. η3-[trans-2,3-bis(methoxycarbonyl)acryloyl]tricarbonylferrate

The crystal structure of a bis(triphenylphosphine)iminium salt of the 1:1 adduct of [FeH(CO)₄]^? and dimethyl acetylenecarboxylate has been determined from three-dimensional X-ray data collected by the counter method. Single crystals belong to the triclinic space space group P$\text{1}$, with two units of [C₃₆H₃₀NP₂]⁺[C₁₀H₇FeO₈]^? in a cell of dimensions: $\text{a}$ = 13.918(2), $\text{b}$ = 15.669(5), $\text{c}$ = 9.909(2) Å, $\text{α}$ = 91.22(3), $\text{β}$ = 94.83(2), and $\text{γ}$ = 77.62(2)°. The structure was refined to a conventional $\text{R}$ of 0.068 for 5373 observed

reflections. The resulting structure indicates that the complex anion is η³-[$\text{trans}$-2,3-bis(methoxycarbonyl)acryloyl]tricarbonylferrate, the coordination around the iron atom being described as a considerably distorted trigonal bipyramid. A comparison of the present structure with the structures of related complexes suggests that the η³-acryloyl portion is best represented as an intermediate of (η³-allyl) with the oxygen atom and (η²-olefin + η¹-acyl). The short Fe-C(acyl) length of 1.897(5) Å implies an enhanced back-donation of electrons from the iron atom to the acyl group.