Cycloaddition reactions of 1,3-benzothiazines—I. : Reactions of 2-phenyl-4-H and 4-phenyl-2H-1,3-benzothiazine derivatives with substituted acetyl chlorides

6,7-Dimethoxy-2-phenyl-4$\text{H}$-1,3-benzothiazine (1) and 6,7-dimethoxy-4-phenyl-2$\text{H}$-1,3-benzothiazine (2) react with substituted acetyl chlorides to give linearly, and new angularly condensed β-lactam derivatives (4,5). Heating of the latter compounds with hydrogen chloride in anhydrous ethanol leads to the formation of the corresponding 4$\text{H}$- and 2$\text{H}$-1,3-benzothiazinium chloride, respectively. The configurations of these compounds (the mutual positions of the substituents relative to the β-lactam ring) were determined by ¹H and ¹³C studies, also making use of the aromatic solvent-induced shifts.     

Determination of traces of lead,cadmium and zinc in copper by an arc-nebulization and flame atomic absorption technique

Arc-nebulization (a thermal nebulization technique) is used to form an aerosol of cadmium, lead and zinc. An open arc chamber of simple operation and an ejector of high efficiency are described which are adaptable for use with any flame atomic absorption spectrometer. Limits of detection better by one or two orders of magnitude than those achieved by conventional flame a.a.s. methods were obtained viz., 43 ng Pb, 5 ng Cd, 7 ng Zn (equivalent to 0.7, 0.08 and 0.11 ppm, respectively, in copper). Calibration with matrix-free solutions was possible for lead and cadmium but not for zinc. The spectral interference of copper on absorbance at the most sensitive zinc line (213.856nm) and the efficiency of arc nebulization of cadmium are also discussed.     

Synthesis of 6H,8H-isoquino[2,3-c][1,3]benzothiazin-8-ones

6H,8H-Isoquino-1,3-benzothiazin-8-ones have been prepared by reaction of 6,7-dimethoxy-2H-1,3-benzo-thiazines with homophthalic anhydride and by photocyclization of 3-benzoyl-4-methylene-6,7-dimethoxy 2H-1,3-benzothiazine. The compounds are thia analogues of protoberberine alkaloids containing a sulfur atom at C-5 and a lactam function at C-8. The mass spectra of the title compounds are discussed.     

Synthesis of quinazolino-1,3-benzothiazine derivatives

The ring-closure reactions of N-(3,4-dimethoxyphenylthiomethyl)-2-nitrobenzamide derivatives 5a,b with phosphoryl chloride gave 4-(2-nitrophenyl)-2H1,3-benzothiazine derivatives 7a,b , which on reduction yielded 4-(2′-aminophenyl)-3,4-dihydro-2H-1,3-benzothiazines 8a,b. Reaction of these compounds with phosgene led to a new heterocyclic ring system, 6H,8H-quinazolino[3,4-c][1,3]benzothiazine derivatives 9a,b. The structures of the title compounds were proved via their ir and nmr (¹H, ¹³C) spectra.     

Application of combined thermoanalytical techniques in the investigation of cyclodextrin inclusion complexes

Citronellol and citronellyl acetate have been entrapped with α-, β- and γ-cyclodextrin (CD). Evolved gas detection and TG-MS coupling was applied to prove the actual inclusion complex formation between monoterpens and CDs. The terpene content was determined by UV-VIS specrophotometry and RP-HPLC and the effect of storage time on the terpene content was also investigated. The α- and γ-cyclodextrin inclusion complexes showed higher thermal stabilities vs. dynamic heating compared to the β-CD complexes. On the contray, the retention of guest using β-cyclodextrin even after 10 years of storage was much more pronounced. Experimental data other than 1:1 complex compositions are assumed. Molecular modeling experiments also suggested multiple complex compositions.     

Synthetic applications of non-polymerizable monomers in living carbocationic polymerization

The foundation and methodology of using highly reactive but non-polymerizable monomers in living cationic polymerizations is introduced. The chemistry and kinetics of 1,1-diphenylethylene (DPE) addition to living polyisobutylene (PIB) in methyl chloride/n-hexanes 40/60 v/v at −80°C is reported. Monoaddition occurred even when large excess of 1,1-diphenylethylene was used. The methanol quenched polymer of the DPE capped PIB carried -OCH₃ functionality exclusively, suggesting that the diphenyl alkyl chain-ends are completely ionized, which was confirmed by conductivity studies. By in-situ functionalization using soft nucleophiles a variety of functional groups were obtained, most notably ester upon reaction with silyl ketene acetal. It was found that the diphenyl carbenium ion is an efficient initiating species for the polymerization of reactive monomers such as vinyl ethers and α-methylstyrene. The synthesis of PIB based block copolymers was accomplished by sequential monomer addition, using para-methylstyrene, α-methylstyrene or isobutyl vinyl ether as the second monomer. It involved capping with DPE, followed by tailoring the Lewis acidity to the reactivity of the second monomer by the addition of titanium(IV) alkoxide, by replacing the Lewis acid with a weaker one or by the use of a common ion salt. PIB-b-PMMA was obtained by the combination of living cationic and group transfer (GTP) polymerizations.     

Determination of Organic Acids in Xylem Sap of Cucumber: Effect of Lead Contamination

Lead, iron, and organic acid concentrations were determined in low-volume xylem sap samples of cucumbers grown in both “lead-free” and lead-contaminated nutrient solutions containing either Fe-citrate or Fe-EDTA by total reflection X-ray fluorescence spectrometry (iron and lead), graphite furnace atomic absorption spectrometry (lead), and reversed-phase high-performance liquid chromatography (organic acids). Three acids of the Krebs cycle—citric, fumaric, and malic acids—were detected and measured. In presence of Fe-citrate the lead contamination results in about three times higher organic acid production in the cucumber compared with the uncontaminated plants. At the same time the amount of transported iron decreases with about 20%. In presence of Fe-EDTA, the same amount of lead leads to a small change in organic acid production; however, the uptake and the transport processes of iron are considerably hindered (35%). Lead transport in the xylem channel was more than one order of magnitude higher when iron was added to the nutrient solution as citrate instead of EDTA complex. These phenomena can be attributed to the participation of the organic acids in the translocation processes of the metals investigated.     

Ueber die Adsorption von Eisen aus Eisenhydroxydsolen und aus Eisenchloridlösungen durch Kaolin und Talkum

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