Manfred Pulst

Kombinierte d-NMR- und LIS-Untersuchungen zum konformativen Verhalten von Formylmethylenthiopyranen

The rotational barriers ΔG≠ toE,Z- ands-cis, s-trans-isomerisation in formylmethylenthiopyranes are determined and discussed with regard to their dependence on substituent effects. Preferential conformers are distinguished by lanthanide induced shifts. Best fits between calculated and experimental shifts are obtained forE,s-trans andZ,s-cis isomers. The results indicate a nonbonding interaction between aldehyde oxygen and ring sulphur, favourings-cis conformation in case ofZ configuration.

Reactivity of a β-trifluoromethyl β-thioacrolein with various electrophiles

Abstract Novel classes of trifluoromethylthiophenes and thiopyrans have been prepared by the reaction of a β-trifluoromethyl β-thioacrolein with different electrophiles, i.e. phenacyl bromide, enones or activated β-chlorovinylpropenes.

2H- und 4H-thiopyrane—eigenschaften, synthesen und reaktionen

Abstract This review presents properties, syntheses, and reactions of 2H- and 4H-thiopyrans, either compounds exhibiting low thermal stability owing to their “non-aromatic” electronic structure or stabilized derivatives with electron-withdrawing group respectively, on an exo-methylene or exo-allylidene group in 2- or 4-position. Such compounds can be drawn with canonic formulas corresponding to donor acceptor systems or charge transfer complexes. After earlier investigations of the pyran-pyrylium ring system the sulfur analogues have found increasing interest during the last twenty-five years. Some of these ring systems are now of technical and scientific interest as electric conductors, dyestuffs, or intermediates for dyes with long wave absorption maxima and as compounds with fluorescent properties, respectively. Several compounds have been investigated for biological activity; interesting in this connection are fluoro substituted derivatives. In this review compilations of characteristic spectroscopic ...

Synthese von substituierten 2-(Ethoxycarbonyl-formyl-methylen)-2H-benzopyranen und ihre Überführung in Polymethinderivate

Summary3-Chloro-2-ethoxycarbonyl crotonic aldehydeC reacts with several 2-hydroxybenzene carbaldehydes and 2-hydroxy-naphthalene-1-carbaldehyde, respectively, to give 2-(ethoxycarbonyl-formyl-methylene)-2H-benzopyrans1a–h under mild conditions. With exception of1c and1d these compounds are mixtures ofE–Z isomers.1a–h easily undergo reactions, e.g. with aniline and derivatives to give2a–e, with various CH-acidic compounds to give3a–h and with 2-alkyl-4,6-diphenyl pyrylium salts to give4a–e. In the presence of alcoholic hydrochloric acid, compounds1 are converted into symmetrical 2,2′-benzopyrylotrimethine salts5a–e which exhibit longwave absorptions from 640–705 nm. These polymethine dyes with ester groups in the methine chain exhibit a remarkable thermal stability.

THE CHEMISTRY OF STABILIZED 2H-THIOPYRANES

Abstract 2H-Thiopyranes with a side chain in position 2 of the ring and a terminal formyl group are resonance stabilized compounds. They represent solid, coloured substances, both thermal stable and also reactive, especially against several nucleophilic reagents. The red coloured 2-(α(-formylmethylene)-2H-thiopyranes are good available by cyclisation reactions starting with β-thioxoaldehydes respectively their derivates, and acceptor substituted 2-chloro-propenes. The Z-s-cis configuration of the side chain was elucidated by 1H-nmr spectroscopy and X-ray analysis. Several reactions lead to prolongation of the side chain, e.g. to the formation of purple 2-(γ-formylallylidene)-2H-thiopyranes. These compounds are very new educts for the synthesis of pentamethine dye stuffs with long wave light absorption maxima. Introduction of alkyl carboxylate groups by synthesis, e.g. use of dimethyl-2-chloro-propene-dicarboxylates, increase the solubility of resulting thiopyranes, but also cause an amazingly steric shiel...

Zur struktur des dimeren β-mercaptozimtaldehyds

Zusammenfassung Versuche zur Darstellung von β-Thioketoaldehyden aus β-Chlorvinylaldehyden und Natriumsulfid fuhrten im Falle der Umsetzung von β-Chlorzimtaldehyd mit Natriumsulfid zur Isolierung einer dimeren Form des β-Mercaptozimtaldehyds. 1 Die Struktur des Dimeren wurde mit Hilfe von IR-, 1H-NMR-und 13C-NMR-Spektren untersucht und als Bicyclo-[3.3.1]-5,7-diphenyl-3-hydroxy-2-oxa-6,9-dithia-nonen-(7) charakterisiert.