Front Cover: Small-Molecule Activation by Heteroleptic Metallasilylenes (Eur. J. Inorg. Chem. 2/2023)

We report on reactions of heteroleptic metallasilylenes L¹(Cl)MSiL² (M=Al 1 , Ga 2 , L¹=HC[C(Me)NDipp]₂, Dipp=2,6-ⁱPr₂C₆H₃; L²=PhC(N^tBu)₂) with CO₂, N₂O, and Me₃SiN₃, yielding the corresponding carbonate complexes L¹(Cl)MOSi(CO₃-κ²O,O−)L² (M=Al 3 , Ga 4 ), silanoic esters L¹(Cl)MOSi(O)L² (M=Al 5 , Ga 6 ), and silaimine L¹(Cl)GaSi(NSiMe₃)L² ( 8 ), whereas {L²Si[N(SiMe₃)Al(Cl)C(Me)NDipp][CHC(Me)N(Dipp)]} 7 was formed by C−C bond cleavage of the L¹ ligand. Compounds 3 – 8 were characterized by NMR (¹H, ¹³C) and IR spectroscopy, elemental analysis and single crystal X-ray diffraction.     

Porphyrins. 17. Oxidation of porphyrins with a cyclopentane ring on the surface of silica gel. Chemical properties of hydroxycyclopentanoporphyrins

It was established that porphyrins with a cyclopentane ring are oxidized on the surface of silica gel by air oxygen to give 5¹-hydroxy-3¹,5¹-cycloporphyrins in 30–35% yields. Heating 5¹-hydroxy-3¹methyl-3¹,5¹-cycloheptaethyl-porphyrin in CF₃COOH leads to splitting out of water and prototropic rearrangement of the intermediate unstable cyclopentenoporphyrin to the previously unknown exo-methylenecyclopentanoporphyrin.See [1] for communication 16.See [2] for our preliminary communication.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 485–489, April, 1984.     

Specialist Periodical Reports. Organometallic Chemistry,Volume 11. : E.W. Abel and F.G.A. Stone,senior reporters. The Royal Society of Chemistry, 1983, xviii + 549 pages, £ 77.

CpNi-vinyl, which is formed as an intermediate in the reaction of nickelocene with vinyllithium, in the presence of ethylene reacts in part via reductive coupling of two vinyl groups to give the binuclear (CpNi)₂(η⁴-butadiene) and in part via ethylene insertion into the vinylnickel bond to give the η¹,η²-3-butenyl complex, which isomerizes at elevated temperatures to the η³-1-methylallyl compound.     

Polysulfonylamine. VII. Aliphatische Trisulfonylamine

Polysulfonyl Amines. VII. Aliphatic Trisulfonyl Amines The compounds N(SO₂R¹)₂(SO₂R²) with R¹ = R² = CH₃ ( 2a ), R¹ = R² = C₂H₅ ( 2b ) and R¹ = CH₃, R² = C₂H₅ ( 2c ) are prepared by cleavage of aminostannanes (CH₃)₃SnN(SO₂R¹)₂ with sulfonyl chlorides R²SO₂Cl. A simple synthesis of 2a from AgN(SO₂CH₃)₂ and CH₃SO₂Cl is described. From the vibrational spectra of 2a , evidence is obtained for a planar NS₃ group in this compound. X-ray structure determinations of 2b and HN(SO₂C₂H₅)₂ ( 3 ) are reported. In 2b , the NS₃ group is approximately planar (S? N? S bond angles 119.0 ± 0.6°, sum of bond angles at N 356.9°); the S? N bond lengths of ca. 173 pm indicate a bond order of 1. In compound 3 , the nitrogen atom has a planar coordination (S? N? S angle 125.3°, sum of bond angles at N 359.3°), the S? N bond lengths of ca. 165 pm correlate with a bond order of 1.3? 1.4.     

N.m.r. studies of a rate process in a bridged biphenyl: Resolution of a discrepancy between n.m.r. and polarimetric kinetic data

Total bandshape analysis of the temperature-dependent n.m.r. spectrum of the bridge methylene protons in 6,6-dicarbethoxy-1,2,3,4-dibenzcyclohepta-1,3-diene has been carried out to yield the following activation parameters: ΔG = 60.96 ± 0.17 kJmol^?1 (14.57 ± 0.04 kcal mol^?1), ΔH^? = 47.3 ± 0.8 kJ mol^?1 (11.3 ± 0.2 kcal mol^?1) and ΔS^? = ?45.6 ± 3.3 J mol^?1 K^?1 (?10.9 ± 0.8 cal mol^?1 K^?1). A value of ΔG^? in agreement with the above may be obtained from a bandshape analysis (at a suitable temperature) of the spectrum of the methylene protons in the carbethoxy groups. In our opinion, the rate process described by these activation parameters must be the configurational inversion of the biphenyl system, and thus the polarimetric data on this compound reported by Iffland and Siegel [J. Am. Chem. Soc. 80, 1947 (1958); half-life of 80 min at room temperature] are seriously called to question, as previously noted by Sutherland and Ramsay [Tetrahedron 21, 3401 (1965)]. We have attempted unsuccessfully to repeat the polarimetric work, and have been able to show by means of thin-layer chromatography in the cold, mass spectral analysis and polarimetry that an optically active impurity (as yet unidentified) is the most probable cause of the discrepancy.     

Chelate von Chinolin-8-ol — Derivaten. XI. Eigenschaften und Struktur von Nickelchelaten alkyl-substituierter Chinolin-8-ole bzw. Chinolin-8-thiole

Reactions of 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete with N? H and P? H Acidic Compounds 1,1,3,3-Tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete, 1 , reacts with aniline to give by opening of the ring 2,2,4,4-tetrakis(dimethylamino)-1-phenyl-1,2λ⁵,4λ⁵-azadiphosphapenta-1,3-diene, 2 , with p-CN? C₆F₄? NH₂ the product is 1-(4-cyano-2,3,5,6-tetrafluorophenyl)-2,2,4,4-tetrakis(dimethylamino)-1,2λ⁵,4λ⁵-azadiphosphapenta-1,3-diene, 3 . t-Butylamine or diethylamine do not react with 1 . Mesitylphosphane opens the ring system 1 forming by reduction of one phosphorus atom {[bis(dimethylamino)phosphanyl]methylidene}bis(dimethylamino)methylphosphorane, 4 . The same product 4 is obtained by reaction with phenylphosphane. The reaction products 2–4 are characterized by their nmr, mass, and ir spectra. Their way of formation is discussed. In 4 a ⁵J(PH), in 3 a ⁷J(CF) long range coupling constant could be identified.     

Synthesis of macrolide antibiotics. 20. Synthesis of erythronolide A

A complete, stereocontrolled synthesis for erythronolide A was carried out by fusion of the (C⁹-C¹³)+(C⁷-C⁸)+(C¹-C⁶) fragments from levoglucosan in 61 steps with 0.28% total yield.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 195–199, January, 1990.     

The photoperoxidation of unsaturated organic molecules--XV. O21Delta g quenching by bilirubin and biliverdin.

Abstract —The use of competitive methods with rubrene as reference acceptor provides values of the rate constants k^B_Q= 2.3 times 10⁹/ mol^-1 s^-1 and k^v_q= 3.3 times 10⁹ mol^-1 s^-1 for the physical quenching of O₂¹δg, by bilirubin (in CCl₄) and biliverdin (in CHCl₃) respectively attributed to electron and energy transfer processes. The rate constant k^B_R= 1.7 times 10⁸/ mol^-1 s^-1 for bilirubin reaction with O₂¹δg is considerably greater than that k^v_R 3 times 10⁸ mol^- s^-1 for the reaction of biliverdin which has identical O₂¹δa, acceptor sites, and is attributed to a primary Type I oxidation process followed by a slower Type II addition of O₂¹δg to the primary products.     

Cation radicals. XXXII. Reaction of N-ethylcarbazole with iodine-silver salts. Nitration of N-ethylcarbazole

Reaction of N-ethylcarbazole ( 1 ) with iodine-silver perchlorate gave a green solution having a singlet esr signal. Reduction of the solution with potassium iodide gave N,N′ -diethyl-3,3′-dicarbazolyl ( 3 , 48%). Small amounts of 3-iodo- ( 4 ) and 3,6-diiodo-N-ethylcarbazole ( 5 ) were also obtained. Compounds 4 and 5 are believed to have been formed by electrophilic iodination of 1 by I₂-AgCIO₄, whereas 3 appears to have been formed via the dimerization of 1 ^.+. In accord with this, reaction of 1 with iodine-silver nitrite gave 3-nitro-N-ethylcarbazole ( 6 , 61%), 9% of another nitro-N-ethylcarbazole ( 7 ), thought to be either 1- or 4-nitro-N-ethylcarbazole, and 28% of 4. Thus, trapping of 1 ^.+ by nucleophilic nitrite ion occurred even though 1 ^.+ is not stable enough toward isolation as the perchlorate.     

Organoborazines. III. Homo- and copolymerization of p-vinylphenylcyclotriborazines

The polymerization and copolymerization with styrene of a series of unsymmetrically B-p-vinylphenyl-N-methyl and N-phenyl borazines [R³(R²)₂B₃N₃(R¹)₃; R¹ = methyl, phenyl, R² = methyl phenyl, R³ = p-vinylphenyl] has been studied. The polymerization of these monomers yielded both tractable and crosslinked materials. The polymers obtained were characterized by ¹H- and ¹³C-NMR spectroscopy, elemental analysis, gel permeation chromatography, and thermogravimeteric analysis. The reactivity ratios for the copolymerization reaction were calculated by the Mortimer-Tidwell method.     

Natural abundance nitrogen-15 n.m.r. spectroscopy. Spin–lattice relaxation in organic compounds

The small negative magnetogyric ratio (γ) of the ¹⁵N nucleus decreases the efficiency of ¹⁵N? ¹H dipole-dipole relaxation to about 25% of that for an analogous ¹³C nucleus. This may lead to greater competition from other relaxation mechanisms in ¹⁵N n.m.r. and consequent partial or total quenching of the negative nuclear Overhauser effect (NOE). In unfavorable circumstances nulling of the ¹⁵N resonance can occur. Previous ¹⁵N relaxation studies have examined isotopically enriched, low molecular weight compounds. The present study examines several small to intermediate size organic compounds containing nitrogen at natural isotopic abundance. In contrast to some of the earlier studies, ¹⁵N? ¹H dipolar relaxation was found to be dominant for protonated nitrogen atoms, even for two tertiary nitrogens (the tertiary amine nitrogen in 1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a] quinolizine and the oxime nitrogen in 3-methyl-2-pentanone ketoxime). The magnitude of the NOE and the moderate value of T₁ indicate effective dipolar relaxation from neighboring but not directly bonded protons in these cases. Nitro groups were found, as expected, to have predominant contributions from non-dipolar mechanisms, and in one case (2-methyl-2-nitro-1, 3-propanediol) signal nulling (NOE of η = ?1) was observed. The effect of paramagnetic impurities was demonstrated for ethanolamine, which contains a basic nitrogen. In this case T₁^DD(¹⁵N? ¹H) = 4·3 s; added Ni(acac)₂ at 1 × 10^?4 Molar reduced the ¹⁵N T₁ to 0·065 s and consequently the NOE to η = 0.     

N.M.R. study of collective molecular motions in smectogen liquid crystals

Abstract

The proton spin relaxation dispersion, T ₁(v), was studied by field-cycling techniques over a broad Larmor frequency range in the nematic and smectic phases of several liquid crystals (4,4′-bis-heptyloxyazoxybenzene, 4-cyano-4′-8-alkylbiphenyl, 4-cyano-4′-9-alkylbiphenyl, 4-cyano-4′-11-alkylbiphenyl and 4-cyano-4′-9-alkoxybiphenyl) with different sites of the nitrogen atom. The results can be explained quantitatively in terms of nematic and smectic order fluctuations (T ₁ ∝ v ^1/2, T ₁ ∝ v ¹), molecular self-diffusion, molecular rotations and up to six cross-relaxation resonances due to a nitrogen-proton coupling The order fluctuations contribution and the transition from the v ^1/2 to the v ¹ dispersion profile occurs always at Larmor frequencies in the kilohertz range. Some additional measurements of the frequency dependence of the dipolar relaxation time T _1D(v), are not in accord with existing theories.     

Indirect A.C. Oscillopolarographic Determination of Total Monomeric and Acid-Reactive Aluminum in Natural Waters by Using Pyrocatechol Violet

ABSTRACT

Indirect determination of total monomelic and acid-reactive aluminum in natural waters by a.c. oscillopolarography in the presence of pyrocatechol violet (PCV) is presented in this paper. In 0.5 mol 1^?1 NH₄Ac buffer solution (pH 6.4) containing l×lO^?3 mol 1^?1 PCV, PCV yields two incisions on the a.c oscillogram at the potentials of - 0.80 and - 1.20 V, respectively. The incision depth declines when adding aluminum in the solution. The decreases of incision depth (Ep = -1.20 V) has a linear relationship with increasing Al concentrations (4×10^?7 - 4×10^?6 mol 1^?). It is the basis for indirect quantitative analysis. The relative standard deviation is 8.3% for 1×10^?6 mol 1^?1 Al (n = 10) and the detection limit is 2 × 10^?7 mol 1^?1. The proposed method has been applied to determine total and acid-reactive Al in natural waters and the results are compared with Driscoll's 8-HQ-MIBK-GF/AAS and PCV colorimetric methods.     

Phosphate Derivatives of Natural Lactones. I. Synthesis of Novel Isoalantolactone Dialkylphosphonates

Novel isoalantolactone dialkylphosphonates were synthesized in 70-87% yields by reacting this eudesmanolide with dialkylphosphites. Their structures were proved by spectral analysis using IR, PMR, ¹³C and ³¹P NMR, and two-dimensional ¹H-¹H (COSY) spectroscopy. The reaction of isoalantolactone with dialkylphosphites is highly stereoselective.     

N.m.r. studies in the heterocyclic series: XVI—determination of the structure of 3-azidoindazole by 1H and 13C n.m.r. spectroscopy

The 1-NH structure for 3-azidoindazole has been demonstrated by the observation of ¹H? ¹H and ¹³C? ¹H couplings involving the hydrogen atom attached to nitrogen. A comparison between 3-azidoindazole and indazole shows that both compounds have the same tautomeric structure.     

Thermodynamic Studies of Bi-Univalent Electrolytes. VI. Thermodynamics of Cadmium Acetate from E. M. F. and Calorimetric Measurements

E. M. F. of the Cell, Cd-Hg (2-phase)/CdAc₂(m), Hg₂Ac₂(s)/Hg was measured at 20°, 25°, 30° and 40°C. The standard e. m. f. of the cell, Cd/CdAc₃(m), Hg₂Ac₂(c)/Hg was evaluated as E°=1.1500?11.09×10^?4T+1.06×10^?8T² The thermodynamic data of the reaction, Cd(c) + Hg₂Ac₂(c)=2Hg(l)+Cd⁺⁺(aq)+2Ac^?(aq) at 25°C were estimated as ΔF°=?42,139, ΔH°=?48,698 cal mole^?1 and ΔS°=?22.0 cal deg^?1 mole^?1 at 25°C. The thermodynamic data for the formation of Hg₂Ac₂(s) were evaluated as ΔF_f°=?202.3, ΔH_f°=?154.5 Kcal mole^?1 and S°=72.9 cal deg^?1 mole^?1. From measurements of the heats of solution of CdAc₂·2H₂O in aqueous solution, the relative partial molal enthalpies of cadmium acetate in aqueous solution were estimated.     

Biosynthesis of cytochalasans. Part 4. The mode of incorporation of common naturally-occurring carboxylic acids into cytochalasin D1.

Utilization of sodium [1-¹⁴C]-, [2–¹⁴C]-, and [1,2-¹³C]-acetates, [1-¹⁴C]-, [1-¹³C]-, or [2-¹⁴C]-propionates, [1-¹⁴C]-or [2-¹⁴C]-malonates, of [1-¹⁴C]- or of [1-¹⁴C]-myristic acid, or of [1-¹⁴C]- and [1-¹⁴C]-palmitic acid in the biosynthesis of cytochalasin D ( 1 ) by Zygosporium masonii was determined by degradation studies or by carbon magnetic resonance spectroscopy. The precursors were incorporated primarily via the acetate-malonate pathway to generate 1 from nine intact acetate units, eight of which are coupled in a head to tail fashion to form the C₁₆-polyketide moiety.     

Porphyrins. 18. Synthesis of octapropylporphyrin by the method of monopyrrole cyclotetramerization of 5-carboxy-2-methoxymethyl-3,4-dipropylpyrrole. Investigation of the thermolysis of meso-N-methylformaldimineocta-propylporphyrin

The synthesis of octapropylporphyrin on the basis of 5-carboxy-2-methoxymethyl-3,4-dipropylpyrrole was realized. It was demonstrated that in the thermolysis of meso-N-methylformaldimineoctapropylporphyrin, 3¹,5¹-cyclo-3¹-ethylidene- and 3¹,5¹-cyclo-3¹-ethyl-5¹-(N-methylimine) derivatives are also formed in addition to 3¹,5¹-cyclo-3¹-ethylhectaporphyrin.See [1] for Communication 17.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 922–927, 1984.     

Low-molecular-mass metabolites of fungi. III. Stachybotrolide fromStachybotrys alternans

The new nitrogen-free compound stachybotrolide has been detected among the products of the vital activity ofStachybotrys alternans. The structure of stachybotrolide has been determined on the basis of IR, mass, and¹H and¹³C NMR spectra. To interpret the latter we have made use of DEPT, 2M NMR¹H−¹H chemical shift correlation (¹H−¹H COSY or HMQC) and 2M NMR correlations of¹H−¹³C long-range interactions (HMBC). Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (371) 120 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 679–683, September–October, 1998.     

Triterpenoidal Secondary Metabolites from Lantana Camara Linn.

Three new pentacyclic triterpenoids, camarin ( 1 ), lantacin ( 2 ), and camarinin ( 3 ) were isolated from the aerial parts of Lantana camara Linn ., together with seven known compounds. The structures of the new constituents were elucidated by chemical transformation, HR‐EI mass spectrometry, and NMR spectroscopy, including 1D (¹H‐ and ¹³C‐NMR) and 2D (¹H,¹H‐COSY, NOESY, ¹H,¹H‐TOCSY, J‐resolved, HMQC, and HMBC) experiments.