Dierk Knittel

Synthese und Thermolyse von α-Azidoacrylestern

By condensation of various aromatic and heterocyclic aldehydes with ethyl azidoacetate or ω-azidoacetophenones substituted vinyl azides were prepared, which yield condensed pyrroles on thermolysis. The mechanism is discussed.ZusammenfassungDurch Kondensation verschiedener aromatischer bzw. heterocyclischer Aldehyde mit Azidoessigester oder ω-Azidoacetophenon wurden substituierte Vinylazide hergestellt, deren Thermolyse zu kondensierten Pyrrolen führte. Der Mechanismus wird diskutiert.

Enazide, 3. Mitt.: Thermolyse von α-Azidozimtestern; Synthese von Indolderivaten

ZusammenfassungDie Thermolyse von α-Azidozimtestern führt über die 2H-Azirine mit sehr guten Ausbeuten zu 2-Indolcarbonestern. Ein Mechanismus für die Enazid-Thermolyse wird diskutiert.AbstractThermolysis of α-azidocinnamates gives, through 2H-azirines a good yield of indol-2-carboxylates. A mechanism of the enazide thermolysis is discussed.

Synthese von α-Azidozimtsäureestern

ZusammenfassungDurch Kondensation von Azidoessigester mit verschieden substituierten Benzaldehyden wurden eine Reihe von α-Azidozimtsäureestern erhalten und deren UV-und IR-Spektren aufgenommen. Die Konfiguration dieser Verbindungsklasse ergibt sich aus NMR-Untersuchungen.AbstractA series of α-azidocinnamic esters has been prepared by condensation of ethyl α-azidoacetate with various substituted benzaldehydes; their IR and UV spectra have been recorded. Conformations of the compounds were assigned on the basis of NMR spectra.

Enazide, 2. Mitt.: Synthese von 1,3-Diaryl-3-azido-propenonen (α-Azidochalkonen)

ZusammenfassungDurch Kondensation von verschiedenen ω-Azidoacetophenonen mit aromatischen Aldehyden wurde eine Reihe von α-Azidochalkonen erhalten.AbstractSome α-azido-chalcones are prepared by condensation of ω-azido-acetophenones with aromatic aldehydes.

Synthese von 1-Aryl-2-azido-2-alken-1-onen

Abstract1-Aryl-2-azido-2-alken-1-ones were obtained by condensing α-azidoacetophenones with aliphatic aldehydes. Thermolysis of these compounds gave azirines, which can be converted to 2-azatricyclo[3.2.1.02.4]-6-octenes by reaction with cyclopentadiene.ZusammenfassungDurch Kondensation von α-Azidoacetophenonen mit aliphatischen Aldehyden wurden 1-Aryl-2-azido-2-alken-1-one erhalten. Die Thermolyse dieser Verbindungen gab Azirine, die sich mit Cyclopentadien in 2-Azatricyclo[3.2.1.02.4]-6-octene überführen lassen.

An electrosynthesis of sulphones

The cathodic reduction of SO2, dissolved in aprotic solvents, to the anion radical SO2− in the presence of organic halides RX results in the formation of organic sulphones R-SO2-R at appreciable current yields. With dihalides, polymeric sulphones or, as in the case ofo-xylylenedibromide, inner sulphinic esters (sultines) are formed, the latter being easily convertible to the corresponding cyclic sulphones.

Eine kleine Elektrolysezelle für organische Synthesen Versuch einer Standardisierung

A versatile electrolysis cell is presented, stable to common organic solvents and easy to handle, which allows organic electrosyntheses to be performed in rather short time under conditions of low voltage, exact separation of anode and cathode compartment and good potential control. Test examples of performance are given.

Electrolytically generated sulfur dioxide anion radical S2O·−4, its absorption coefficient and some of its decay reactions

Abstract The electrochemical reduction of SO 2 in dimethylformamide at Pt electrodes finally leads to the red species S 3 O 2− 6 via the blue complex S 2 O ·− 4 . The UV-VIS absorption coefficients are determined: ϵ(S 2 O ·− 4 ) = (224 ± 25) × 10 5 cm 2 mol −1 ; ϵ(S 3 O 2− 6 ) = (0.64 + 0.07) × 10 5 cm 2 mol −1 . A calculation of the complexing constant of SO 2 with free SO ·− 2 radical based on potential shifts confirms this constant to be in the range of 200–700 1 mol −1 . Two potentiometric titration methods (viz: with allylbromide and tetraethylammoniumtribromide) for analysis of electrolytically generated S III -oxo-anions in DMF are presented. Reactions of those anions with aromatic aldehydes and trials for trapping of possibly formed SO are described.

Synthese von ungesättigten und gesättigten Aminosäurederivaten durch kathodische Reduktion von Azidozimtsäureester

Cathodic reduction of α-azidocinnamic ester under aprotic conditions on Hg, Pt, or graphite electrodes can be directed to high yields of N,N-diacylated dehydroaminoacid derivates (f.i. addition of acetic anhydride) or to almost quantitative yields of α-aminocinnamic ester in very pure form by careful addition of H+-donors. The dehydroamino compounds in turn can be further reduced to the corresponding saturated compounds by following H+-addition and changed electrolysis potential. Almost no dimerization occurs.

Cathodic reduction of SO2 in the presence of organic dihalides

The reaction of the electrolytically generated SO2− anion radical with 1,θ-dihalides is used for the synthesis of sulfur containing heterocycles like oxathiolane-, oxathiane-, thiane- and thiepane-oxides. 1,2-Dihalides are reductively deblocked to give olefines.ZusammenfassungDie Reaktion des elektrolytisch erzeugten SO2−-Anionradikals mit 1,θ-Dihalogeniden führt zu schwefelhaltigen Heterocyclen wie Oxathiolan-, Oxathian-, Thian- und Thiepanoxiden. 1,2-Dihalogenide geben durch reduktive Eliminierung Olefine.