Sulfurisation of Amino Tetraphosphorus Trichalcogenide Compounds

Amino tetraphosphorus trisulfides α-P₄S₃(NR¹R²)₂ reacted with S₈ under photolysis using visible light, in moderate or low conversion, to give α-P₄S₃(S)(NR¹R²)₂, in which the added sulfur atom was exocyclic. For NR¹R² = NPr₂ⁱ, three isomers were found: a pair of diastereomers corresponding to attachment of the sulfur atom to a nitrogen-carrying phosphorus atom either with retention or with inversion of its configuration, and an isomer containing a sulfurised bridgehead phosphorus atom. For NR¹R² = NMePh, only the two diastereomers were seen. Photolysis of a mixture of α-P₄Se₃(NMePh)₂ and α-P₄Se₃(NMePh)I with S₈ gave as major products α-P₄SSe₂(NMePh)₂ and α-P₄SSe₂(NMePh)I, in which sulfur had replaced the bridging selenium atom in the starting compounds. This provides a synthesis of compounds α-P₄SSe₂XY in which sulfur occupies a specific skeletal position, rather than being randomly distributed. All products were characterised by ³¹P NMR in unseparated solutions. Ab initio MO calculations of geometry and of GIAO NMR chemical shifts at the 3-21G* level for three isomers of the unknown model compound α-P₄S₃(S)(NH₂)₂, and two isomers of α-P₄S₃(NH₂)₂, allowed identification of the observed isomer of α-P₄S₃(S)(NPr₂ⁱ)₂ with a sulfurised bridgehead, but relative assignment of the two diastereomers to their NMR parameters remains a hypothesis.     

Stereoisomeric complexes of Pt(II) with threonine and allothreonine

The paper describes the synthesis of geometrical isomers and diastereomers of Pt(II) bischelates with diastereomeric hydroxy-amino acids threonine (threo-α-amino-β-hydroxybutyric acid CH₃C*H(OH)C*H(NH₂)COOH=ThrH) and allothreonine (erythro-α-amino-β-hydroxybutyric acid=alloThrH) containing two asymmetric carbon atoms C*: cis-,trans-[Pt(S-Thr)₂], cis-,trans-[Pt(RThr)(S-Thr)], cis-,trans-[Pt(R-alloThr)(S-alloThr)] (where R and S are the absolute configurations of the asymmetric carbon atom bonded to the carboxyl group). ¹⁹⁵Pt NMR spectroscopy is used to investigate the successive phases of the synthesis of the stereoisomeric Pt(II) complexes with threonine. The synthesized complexes are studied by ¹H, ¹³C, ¹⁹⁵Pt NMR spectroscopy, IR spectroscopy, and single crystal XRD.     

Stereochemistry of the products of reductive amination of 2,6-bis[(2-oxocyclohexyl)methyl]cyclohexanone, an alicyclic 1,5,9-triketone

The reductive amination of alicyclic 1,5,9-triketone—2,6-bis[(2-oxocyclohexyl)methyl]cyclohexanone—has been studied under Leuckart reaction conditions and in the presence of NaBH₃CN. A mixture of diastereomers of quinolizidine structure (2,3,5,6-bistetramethylenehexahydrojulolidine) is obtained. The stereochemistry of seven isomers is determined by the study of their NMR spectra using 2D NMR experiments (¹H-¹H COSY, HSQC, and HMBC).     

Synthesis,spectroscopic and configurational study,and ab initio calculations of new diazaphospholanes

New 2-substituted diazaphospholane-2-oxides (I-III, V-VIII) and diazaphosphorinane-2-oxide (IV) were synthesised and characterised by ¹H, ¹³C, and ³¹P NMR, IR spectroscopy, and elemental analysis. The presence of chiral diamino groups in compounds II and V–VIII gives rise to various diastereomers so that the ³¹P{¹H} NMR spectra demonstrated three and two peaks with different ratios, respectively. Also, the ¹H and ¹³C{¹H} NMR spectra of compounds II and V–VIII revealed three and two sets of signals for the related conformers (diastereomers). Interestingly, the ³¹P NMR spectrum of V in D₂O indicated a great upfield shift (Δδ = 19.0) for ³¹P relative to the value obtained in DMSO-d₆ (solvent effect). The two signals in V split further to three signals in the presence of β-cyclodextrin. Moreover, conformational analysis of diazaphospholane V was studied by ab initio calculations at the HF and B3LYP levels of theory using the Gaussian 98 program. Results indicated that among four suggested diastereomers (C1–C4) of V, C1 and C3 containing methyl group in the equatorial position are the most stable forms.     

Alkyl‐Tethered Bis‐Phosphoryl Compounds with two 1,3,2‐Benzodiazaphosphorinone Units; Oxidation,Complexation, and X‐Ray Structure Analysis of Selected Compounds

The reaction of the bis‐chlorophosphines 1 a – 1 d with bis(2‐chloroethyl)amine hydrochloride in the presence of triethylamine and with various trimethylsilylamines led to a new class of bis‐phosphorus ligands 2 a – 2 c and 3 a – 3 g . ³¹P‐NMR studies suggested that the bis‐phosphorus ligands undergo rotation reactions about the alkyl bridge in polar solvents. Compounds 2 a – 2 c showed initially only one sharp singlet each in their ³¹P‐NMR spectra. After a few days at room temperature, two signals were observed. Similar results were observed for 3 a – 3 g . In the solid state, the two phosphorus atoms in 2 c are not equivalent, as was confirmed by the observation of two signals in the solid state ³¹P‐NMR spectrum. Oxidation reactions of 2 a – 2 c by the hydrogen peroxide‐urea 1 : 1 adduct (NH₂)₂C(:O) · H₂O₂ led to the formation of the corresponding phosphoryl compounds 4 a – 4 c . Reaction of 2 a and 3 a with Pt[COD]Cl₂ (COD = 1.5‐Cyclooctadiene) furnished the complexes 5 and 6 . The NMR spectra suggested that the two chlorine atoms are in cis position. X‐ray structure analyses were conducted for 2 a , which exhibits twofold symmetry; 2 c , which is linked into dimers by hydrogen bonds C–H…O; and 6 , confirming the cis configuration.     

Beiträge zur Chemie des Phosphors. 105. 1,2,3,4-Tetraphenyl-1,4-bis(trimethylsilyl)-tetraphosphan und 1,2,3,4-Tetraphenyltetraphosphan

Contributions to the Chemistry of Phosphorus. 105. 1,2,34-Tetraphenyl-1,4-bis(trimethylsilyl)-tetraphosphane and 1,2,3,4-Tetraphenyltetraphosphane 1,2,3,4-Tetraphenyl-1,4-bis(trimethylsilyl)-tetraphosphane, Me₃Si? (PPh)₄? SiMe₃ ( 1 ), is obtained by reacting K₂(PPh)₄ with trimethylchlorosilane under suitable conditions. Compound 1 disproportionates almost easier than the corresponding triphosphane (Me₃Si)₂(PPH)₃. Of the six possible diastereomers only 1a (erythro, meso, erythro), 1b (erythro, d,l, erythro), 1 d (threo, d,l, threo), and 1 f (erythro, threo, threo) can be detected in solution by ³¹P-NMR spectroscopy. In consequence of rapid inversion at the P atoms a dynamic equilibrium exists between the different isomers. The assignment of the ³¹P-NMR-spectroscopically observed spin systems to the corresponding diastereomers results from the dependence of the ¹J_PP-coupling constants on the dihedral angle between vicinal free electron pairs as well as on the observed frequency distribution. In the alcoholysis of 1 the corresponding hydride H? (PPh)₄? H ( 2 ) is formed as the main product. It could be isolated in spite of its instability. At room temperature 2 disproportionates rapidly forming mainly (PPh)₄ and H₂(PPh)₂ (ratio 1:2) at first; later on also H₂(PPh)₃, H₂PPh, and (PPh)₅ are found. The corresponding rearrangements follow a four-center mechanism involving predominantly P? P bonds.     

Hydrogen‐Bonding in Cyclic 2‐(3‐Oxo‐3‐phenylpropyl)‐Substituted 1,3‐Diketones: 17O‐NMR Spectra and X‐Ray Structure Determination

Structures of cyclic 2‐(3‐oxo‐3‐phenylpropyl)‐substituted 1,3‐diketones 4a – c were determined by ¹⁷O‐NMR spectroscopy and X‐ray crystallography. In CDCl₃ solution, compounds 4a – c form an eight‐membered‐ring with intramolecular H‐bonding between the enolic OH and the carbonyl O(11)‐atom of the phenylpropyl group, as demonstrated by increased shielding of specifically labeled 4a – c in the ¹⁷O‐NMR spectra (Δδ(¹⁷O(11))=36 ppm). In solid state, intermolecular H‐bonding was observed instead of intramolecular H‐bonding, as evidenced by the X‐ray crystal‐structure analysis of compound 4b . Crystals of compound 4b at 293 K are monoclinic with a=11.7927 (12) Å, b=13.6230 (14) Å, c=9.8900 (10) Å, β=107.192 (2)°, and the space group is P2₁/c with Z=4 (refinement to R=0.0557 on 2154 independent reflections).     

Beiträge zur Chemie des Phosphors. 200. Tetraisopropyl-tetradecaphosphan(4), P14(i-Pr)4 – Darstellung und strukturelle Charakterisierung

Contributions to the Chemistry of Phosphorus. 200. Tetraisopropyl-tetradecaphosphane(4), P₁₄(i-Pr)₄ – Preparation and Structural Characterization Tetraisopropyl-tetradecaphosphane(4) ( 1 ) has been obtained by reacting i-PrPCl₂, P₄, and magnesium and subsequently thermolysing the crude reaction product, and has been isolated in pure form. Whereas the ³¹P{¹H}-NMR spectrum provides only limited structural information, the ¹³C{¹H, ³¹P}-DEPT-NMR and the ¹H{³¹P}-NMR spectrum of 1 reveals the presence of two symmetrical configurational isomers 1a and 1c and one asymmetrical diastereomer 1b . This would only be possible, if 1 is 3,4,10,11-tetraisopropyl-hexacyclo[6.6.0.0^2,6.0^5,14.0^7,12.0^9,13]tetradecaphosphane. When crystallizing 1 pure 1a precipitates, which at +10°C in solution is retransformed into the isomeric mixture 1a , 1b , 1c by inversion of the configuration.     

Reductive Coupling Reaction of Aryliminomethylferrocenes with Triethyl Orthoformate Induced by Low‐valent Titanium

Reductive coupling reaction of aryliminomethylferrocenes FcCH = NAr[(1, Ar=QHs (a), p‐ClC₆H₄ (b), p‐BrC₆H₄ (c), p‐CH₃C₆H₄ (d), m‐ClC₆H₄ (e)] with triethyl orthoformate (2) in Zn‐TiCl₄ system gave three kinds of products: 1, 3‐diaryl‐4, 5‐diferrocenyl imidazolidines (3), N, N‐disubstituted formamides (4), and 1, 2‐diferrocenyl ethylene (5). ¹H NMR spectra proved that all the compounds 3 obtained were dl‐isomers. All the new compounds 3 and 4 were characterized by elemental analysis, ¹H NMR, ¹³C NMR (for 3) and IR spectra. The molecular structure of 3c was determined by X‐ray diffraction.     

NMR and Molecular Mechanics Studies on Configurational Isomerism and Conformational Equilibrium of Chiral Cyclohexenones

Chiral diastereomers of 2-isopropyl-5-methyl-6-(4-phenyl)benzylcyclohex-2-enone and their isomer 2-(4-phenylbenzyl)-3-methyl-6-isopropylcyclohex-2-enone, which are products of an acid-catalyzed intramolecular rearrangement of 3R,6R-2-(4-phenylbenzylidene)-3-methyl-6-isopropylcyclohexanone, were investigated to show that conformational analysis by molecular mechanics and ¹H NMR spectroscopy permits an integrated solution of three structural problems: double bond location in an aliphatic ring for isomeric products; determination of the stereochemical configuration for the two diastereomers; evaluation of the conformational equilibrium between the diastereomers. Based on the results of calculations, this is achieved by estimating the configuration- and conformation-sensitive proton spin–spin coupling constants of the cyclohexenone ring for alternative structures and correlating them with ¹H NMR data.     

Preparation,Reactions, and Stereochemistry of 4-Tert-Butyl-1-Chlorophosphorinane 1-Sulfide and Derivatives

Abstract

Nucleophilic substitution at tetracoordinated phosphorus centers has been extensively investigated.¹ Transesterification of acyclic phosphinates proceeds with inversion of configuration,² whereas four-membered phosphinates react with retention.³ In previous work⁴ we suggested that transesterification in six-membered phosphinates occurs via an S_N2 mechanism. The title compound was synthesized as a model structure to study the stereochemical and mechanistic aspects of nucleophlic substitution at phosphorus in a six-membered ring. A mixture of diastereomers was produced and separated by column chromatography. Both the mixture and separate isomers were used for an investigation of substitution with methanol, methoxide ions, and phenoxide ions; the reactions proceeded with inversion. Transesterification reactions of the resulting thiophosphinates were studied and found to proceed with inversion. Reactions of these with phenyllithium, benzyllithium, lithium phenylacetylide, and the corresponding organomagnesium halides were also carried out. The stereochemical assignments for the title compound (cis and trans) and two derivatives have been firmly anchored by X-ray studies;⁵ assignments for others are tentative and based on spectroscopic measurements, including ¹H, ¹³C, and ³¹P NMR data.     

Structure elucidation of β-carotene isomers by HPLC-NMR coupling using a C30 bonded phase

The separation of cis/trans isomers of β-carotene has been performed with a C₃₀ stationary phase employing ¹H NMR spectroscopy as an on-line detection technique. 1D as well as 2D NMR spectra have been recorded in the stopped-flow mode for the predominant chromatographic peaks. Structural assignment of the five identified isomers was performed via comparison of simulated 1D ¹H NMR spectra on the basis of the structures of β-carotene cis/trans isomers with the experimental data, and also by the analysis of the proton-proton connectivities in the 2D NMR spectra of three isomers with the highest concentration. The chromatographic retention behaviour of the isomers agreed well with previously reported data. The advantage of the applied hyphenated coupling technique compared to conventional off-line techniques lies in the fact that chromatographic separation and NMR detection are performed in a closed system, so that reisomerization of the separated compounds is inhibited. Received: 29 May 1996 / Revised: 1 July 1996 / Accepted: 4 July 1996     

Electron impact ionization mass spectrometry and tandem mass spectrometry of phenylalkylpyridazines

The mass spectrometric fragmentation behaviour of pyridazine and four monosubstituted derivatives containing a pbenylalkyl side-chain (3- and 4-benizylpyridazine, 3- and 4-(2-pbenylethyl)pyridazine) was investigated. In the electron impact ionization mess spectra of the 3-substituted compounds abundant [M – H]⁺ peaks are observed. This allows a clear distinction between 3- and 4-substituted pyridazines, as the spectra of the latter isomers show only very weak [M – H]⁺ signals. The stability of [M – H]⁺ ions derived from 3-alkylpyridazines (deduced from only the very low abundance of further fragment ions) gives strong evidence for a cyclic structure of these ions. One fragmentation pathway typical of the parent pyridazine, the [M - N₂] fragmentation, was not detectable with any of the phenylalkylpyridazines investigated. Instead, loss of HCN, H₃CN⁺ and N²H⁺ was observed. An interesting fragmentation, observed with 3-(2-phenylethyl)pyridazine, is the loss of ⁺CH₃ from the molecular ion and also from the [M – H]⁺ ion.     

Structure elucidation of β-carotene isomers by HPLC-NMR coupling using a C30 bonded phase

The separation of cis/trans isomers of β-carotene has been performed with a C₃₀ stationary phase employing ¹H NMR spectroscopy as an on-line detection technique. 1D as well as 2D NMR spectra have been recorded in the stopped-flow mode for the predominant chromatographic peaks. Structural assignment of the five identified isomers was performed via comparison of simulated 1D ¹H NMR spectra on the basis of the structures of β-carotene cis/trans isomers with the experimental data, and also by the analysis of the proton-proton connectivities in the 2D NMR spectra of three isomers with the highest concentration. The chromatographic retention behaviour of the isomers agreed well with previously reported data. The advantage of the applied hyphenated coupling technique compared to conventional off-line techniques lies in the fact that chromatographic separation and NMR detection are performed in a closed system, so that reisomerization of the separated compounds is inhibited. Received: 29 May 1996 / Revised: 1 July 1996 / Accepted: 4 July 1996     

Secondary interactions in n‐(chloromethyl)pyridinium chlorides (n = 2, 3, 4)

In the isomeric title compounds, viz. 2‐, 3‐ and 4‐(chloro­methyl)pyridinium chloride, C₆H₇ClN⁺·Cl^?, the secondary interactions have been established as follows. Classical N—H?Cl^? hydrogen bonds are observed in the 2‐ and 3‐isomers, whereas the 4‐isomer forms inversion‐symmetric N—H(?Cl^??)₂H—N dimers involving three‐centre hydrogen bonds. Short Cl?Cl contacts are formed in both the 2‐isomer (C—Cl?Cl^?, approximately linear at the central Cl) and the 4‐isomer (C—Cl?Cl—C, angles at Cl of ca 75°). Additionally, each compound displays contacts of the form C—H?Cl, mainly to the Cl^? anion. The net effect is to create either a layer structure (3‐isomer) or a three‐dimensional packing with easily identifiable layer substructures (2‐ and 4‐isomers).     

13C NMR spectra of 2,3-dihydro-1H-benzo[b]azepines: Differentiation of diastereomers

The ¹³C NMR spectra of 23 2,3-dihydro-1H-benzo[b]azepines, including nine pairs of diastereomers separated by chromatography, [(2R*, 3R^*) and (2R^*), 3S^*)] are hereby assigned and discussed. The relative configurations of the diastereomers were assigned by two methods. The first, based on the chemical shifts of the asymmetric carbons C-2 and C-3 (with regression analysis), shows that the values for (R^*, R^*) are approximately 1 ppm lower than those for (R^*, S^*) diastereomers. The second method uses the chemical shifts, δ₃, of the R₃(CH₃) substituents. When these δ₃ values are compared by means of the δ₃-δ_m difference (δ_m is the mean value obtained from compounds where R₂=H), the difference is always negative for (R^*, R^*) and positive for (R^*, S^*). This is attributed to a γ-gauche effect between R₂ and R₃ in the case of (R^*, R^*) diastereomers (R₂ and R₃ are cis). The results corroborate those already obtained by ¹H NMR [J(23)(R^*, R^*)<J(23)(R^*, S^*)] and are a confirmation of the results of a radiocrystallographic examination carried out on two nitrogen acetylated diastereomers.     

Proton-transfer salts of diphenylphosphinic acid with substituted 2-aminopyridine: crystal structure,spectroscopic and DFT studies

Three proton-transfer salts of diphenylphosphinic acid (DPPA) with 2-amino-5-(X)-pyridine (AMPY, X = Cl, CN or CH₃), namely, 2-amino-5-chloropyridinium diphenylphosphinate, C₅H₆ClN₂⁺·C₁₂H₁₀O₂P⁻ ( 1 , X = Cl), 2-amino-5-cyanopyridinium diphenylphosphinate, C₆H₆N₃⁺·C₁₂H₁₀O₂P⁻ ( 2 , X = CN), and 2-amino-5-methylpyridinium diphenylphosphinate, C₆H₉N₂⁺·C₁₂H₁₀O₂P⁻ ( 3 , X = CH₃), have been synthesized and characterized by FT–IR and ¹H NMR spectroscopy, and X-ray crystallography. The crystal structures of compounds 1 – 3 were determined in the space group P for 1 and 2 , and C2/c for 3 . All three compounds contain N—H…O hydrogen-bonding interactions due to proton transfer from the O=P—OH group of DPPA as donor to the pyridine N atom of AMPY as acceptor. The proton transfer of compounds 1 – 3 was also verified by ¹H NMR and FT–IR spectroscopy. The stoichiometry of all three proton-transfer salts was determined to be 1:1 and the Benesi–Hildebrand equation was applied to determine the formation constant (K_CT) and the molar extinction coefficient (ϵ_CT) in each case. Theoretical density functional theory (DFT) calculations were performed to investigate the optimized geometries, the molecular electrostatic potentials (MEP) and the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) of all three proton-transfer salts. The results showed good agreement between the experimental data and the DFT computational analysis.     

Peculiarities of the three-dimensional structures of isomers of 1,2,5-trimethyl-4-amino(amido)piperidines from the 1H and 13C NMR spectra

The three-dimensional structures of seven 1,2,5-trimethyl-4-amino(amido)piperidines were studied by means of the ¹H and ¹³C NMR spectra. The ³J_HH values and the ¹³C chemical shifts indicate that the substituents in the piperidine ring of all of the 2c,5c,4r isomers have a 2e,4e,5a orientation, while those in the piperidine ring of all of the 2c,5t,4r isomers have a 2e,4e,5e orientation. The conformational change (as a result of ring conversion) 2e,4a,5e 2a,4e,5a was observed for the 2t,5c,4r isomers on passing from the corresponding amine to the amide; this change is associated with striving of the more bulky amide substituent to become equatorially oriented. Retarded rotation about the C₍₄₎-N bond was observed in the 2c,5t,4r isomer of the 4-(N-phenylbenzamido) derivative; this is explained by steric hindrance due to the 5e-CH₃ group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 54–57, January, 1988.The authors thank I. I. Chervin for assistance in recording the NMR spectra with a WM-400 spectrometer.     

Electron impact mass spectra of polycyclic aromatic compounds with several types of pyridino- and benzobenzanthrone skeletons

Electron impact mass spectra were measured for five isomers of pyridinobenzanthrones and three isomers of benzobenzanthrones. The fragmentation pattern and intensity of M²⁺, [M – H]⁺, [M – CO]ⁱ⁺, [M – CO – H(or 2H)]ⁱ⁺ and [M – CO – HCN]ⁱ⁺ (i = 1, 2) ions indicated remarkable differences and very interesting features according to the isomers with or without nitrogen and condensation positions of a pyridino or benzo ring to the benzanthrone skeleton. Further, the competition of decompositions through [M – H]⁺, [M – CO]^+˙ or [M – HCN]^+˙ ions was confirmed by the observation of metastable ions and the appearance energies of fragment ions. Interesting observations from these results were expulsion of an H atom in close proximity to the area around an O?C group, a weak bonding interaction between sp² C? H and an O?C group, inducing specific hydrogen rearrangement, and characteristic charge localization on heteroatoms.     

Structural Dynamics and Stereoselectivity of Chiral Benzylideneamine N,C-Chelate Borane Photo–Thermal Isomerization

New chiral N,C-chelate organoboron compounds based on benzylideneamines (bza) with the general formula of B(bza-R)Mes₂ (R=H or Me; Mes=mesityl) are reported. A chiral substituent group R- or S-CH(CH₃)Ph (Ph=phenyl) was introduced to the imine center, which imposed a previously unobserved pseudo- or axial-chirality on the BMes₂, creating distinct diastereomers. NMR spectroscopic studies established that the diastereomers undergo slow exchange in solution at ambient temperature. The chiral N,C-chelate B(bza-R)Mes₂ molecules undergo photoisomerization in the same manner as their non-chiral analogues, generating chiral BN-cyclooctatriene (BN-COT) derivatives. Most significantly, by tracking the photoisomerization with circular dichroism (CD) and ¹H NMR spectra along with time-dependent density functional theory (TD-DFT) computational studies, the photoisomerization was established to proceed in a highly stereoselective manner, that is, one diastereomer converts exclusively to the corresponding diastereomer product in the photoreaction.