The synthesis of dendrodoine, 5-[3-(N,N-dimethylamino- 1,2,4-thiadiazolyl]-3-indolylmethanone,a metabolite of the marine tunicate dendroda grossular

The cytotoxic natural product dendrodoine has been synthesised by a 1,3-dipolar addition reaction between indolyl-3-carbonyl nitrile and N,N-dimethylaminonitrile sulphide generated $\text{in}$$\text{situ}$ through the thermolysis of 5-(N,N-dimethylamino)-1,3,4-oxathiazol-2-one.     

Solid products from thermal decomposition of polyethylene terephthalate: Investigation by CP/MAS 13C-NMR and fourier transform-IR spectroscopy

The solid reaction products from pyrolysis of polyethylene terephthalate in the presence and absence of red phosphorus were characterized by CP/MAS ¹³C-NMR, FR-IR, and MAS ³¹P-NMR spectroscopy. Over the temperature range of 300–400°C, polyethylene terephthalate was converted in a sealed vial to a highly crosslinked polymer of terephthalic acid. Pyrolysis in the presence of red phosphorus, which functions as a flame retardant by increasing the amount of char, yielded an intractible polyaromatic phosphate ester. After thermal cleavage of polyethylene terephthalate with formation of free carboxyl and vinyl ester groups, there are two competing reaction pathways. The smaller molecular weight fragments may enter the vapor phase where they undergo further degradation primarily to CO₂, CO, and acetaldehyde, as described by others. However, if volatilization of the oligomeric fragments is inhibited, an alternate reaction pathway gives rise to the formation of highly crosslinked char. Red phosphorus decreases the volatility of the oligomeric fragments by converting them to phosphates and thereby enhances char formation.     

The thermal decomposition of aluminium sulfate

The mechanism of thermal decomposition of aluminum sulfate has been investigated in the 500–700°C temperature range using a flow reactor system with the emitted gaseous sulfur oxides collected in a Goksøyr—Ross coil and a hydrogen peroxide impinger. Sulfur trioxide (SO₃) was found to be the primary sulfur oxide released during thermal decomposition (1).

Less than 3% of the released sulfur oxides were sulfur dioxide (SO₂), indicating that the SO₃ dissociation reaction (2) is slow relative to the residence time of the SO₃ in the reactor (～ 1 sec).

The experimental technique should be readily adaptable to the study of the thermal decomposition of other metal sulfates.     

Investigation of the phosphinyl analog of α-ketoglutaric acid

It was shown by³¹P and¹³C NMR spectroscopy that methyl(3-carboxy-3-oxopropyl)phosphinic acid (4-methylhydroxyphosphinyl-2-oxobutyric acid) (1) and the amide (2) of the latter exist in keto forms in non-aqueous solutions. In aqueous solutions an equilibrium between the keto,gem-diol, and enol forms has been observed. The proportions of the diol and enol forms increase as the acidity of the media increases. Silylation of acid 1 with hexamethyldisilazane gives the tris(trimethylsilyl) derivative of enol form (3) (Z- andE-isomers).Translated fromIzyestiya Akadetnii Nauk. Seriya Khimicheskaya, No. 1, pp. 125–128, January, 1994.     

Photophysics and photochemistry of sterically strained α-haloanthraquinones: The bromo and/or chloro substituted compounds

The steric hindrance between the oxygen and halogen atoms results in the structural deformation of α-haloanthraquinones and their lowest excited triplet (T₁) states are of mixed nπ ^*-ππ ^* or ππ ^* character with unusually short lifetimes. Moreover, the rates of hydrogen-atom abstraction from ethanol by the T₁ states decrease with their increasing ππ ^* character, and the proximity of the halogen atom to the hydroxy group causes the photochemical intramolecular elimination of hydrogen halide from the initial photoproducts (α-haloanthrahydroquinones) yielding α-haloanthraquinones (or anthraquinone) with one less halogen atom than the original molecule; the final product is anthrahydroquinone. The remarkably large structural deformation of 1,8-dihaloanthrasemiquinone radicals which gives rise to the simultaneous formation of 1,8-dihaloanthrahydroquinones and the original anthraquinones. Of particular interest is observation of the absorption band(s) attributable to the second excited triplet (T₂) states of 1,8-dihaloanthraquinones. However, the electron transfer from triethylamine (TEA) to these T₂ states generating the radical anions is observed only in acetonitrile, while that to the T₁ states generating their exciplexes with TEA is observed not only in acetonitrile but also in toluene and ethanol.     

S-4-methylphenyl-o,o-bis[1-benzotriazolyl] phosphorothioate: a versatile phosphorylating agent

The phosphorylating agent obtained by treatment of S-4-methylphenyl phosphorodichloridothioate with 1-hydroxybenzotriazole can not only be applied for the introduction of polyphosphate functions at the terminal ends of nucleic acids, but also for the formation of 3′-5′-phosphotriester linkages.     

Analogs of pyrimidine nucleosides

α-(1-Cytosinyl)-γ-butyrolactone was obtained by condensation of bis(trimethylsilyl)cytosine with α-bromobutyrolactone. The reduction of α-(1-cytosinyl)-γ-butyrolactone with sodium borohydride gave N₁-(1,4-dihydroxy-2-butyl)cytosine, the acylation of which with benzoyl chloride and subsequent partial hydrolysis gave N₁-(1,4-dihydroxy-2-butyl)-N₄-benzoylcytosine.     

Rapid analysis of small glass fragments by atomic-absorption spectroscopy

A rapid method is described for the determination of magnesium, iron and manganese in small glass fragments (250-500 mug). The speed of the analytical procedure is made possible by the use of a convenient cold digestion stage allied to a discrete sampling method which permits the three elements of interest to be determined by flame atomic-absorption spectrophotometry.     

Crystal and molecular structure of 1-aza-6′-(3′-oxo-5′, 5′-dimethyl-δ1′-pyrrolin-3′-yl)methylidene-2,2,7,7-tetramethyl-4-hydroxybicyclo-[2.2.21azaoctane

An x-ray structural study has shown that 6-(3-oxo-5,5-dimethyl-¹-pyrrolin-3-yl)methylidene-2,2,7, 7-tetramethyl-4-hydroxybicyclo[2.2.2]azaoctane is formed as a low-molecular-weight byproduct of the solid-phase polymerization of 1,4-bis(2,2,6,6-tetramethyl-4-hydroxy-4-piperidyl)butadiyne.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 585–587, March, 1990.