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Dive into the research topics where Gerhard Hojas is active.

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Featured researches published by Gerhard Hojas.


Molecules | 2001

Malonates in Cyclocondensation Reactions

Wolfgang Stadlbauer; El-Sayed A. M. Badawey; Gerhard Hojas; Peter Roschger; Thomas Kappe; Karl-Franzens-University Graz

The use of malonates such as diethyl malonates 9, (chlorocarbonyl)ketenes 15 and bis(2,4,6-trichlorophenyl) malonates 18 as reagents for cyclocondensation with 1,3-dinucleophiles to give six-membered heterocycles is described. Further attempts to use malonates such as bis(trimethylsilyl) malonates 19 and bis(carbamimidoyl) malonates 29 as new cyclocondensation agents are described .


Journal of Biochemical and Biophysical Methods | 2002

Study of the thermal behavior of azidohetarenes with differential scanning calorimetry.

Wolfgang Stadlbauer; Gerhard Hojas

Thermal properties of azidohetarenes without reactive ortho-substituents, obtained by DSC analysis, were compared with the DSC data of ortho-phenyl and ortho-acyl substituted azidohetarenes, which give ring closure reactions either to indoles or to five-membered heterocycles such as isoxazoles. The reaction temperatures and reaction enthalpies give both information to prepare the reaction conditions and important safety information and were, in addition, used to find out relations between the temperatures or enthalpies with the three different reaction mechanisms.


Journal of The Chemical Society-perkin Transactions 1 | 2000

Synthesis of 4-azido-3-diazo-3H-pyrazolo[3,4-b]quinoline from 3-amino-4-hydrazino-1H-pyrazolo[3,4-b]quinoline

Wolfgang Stadlbauer; Gerhard Hojas

The reaction of 3-amino-4-hydrazino-1H-pyrazolo[3,4-b]quinoline 8 with nitrous acid did not give 2,4-diazidoquinoline-3-carbonitrile 5 as reported previously, but afforded in 60% yield 4-azido-3-diazopyrazolo[3,4-b]quinoline 10, which gave by azo coupling with 2-naphthol 4-azido-3-(2-hydroxy-1-naphthylazo)-1H-pyrazolo[3,4-b]quinoline 11.


Journal Fur Praktische Chemie-chemiker-zeitung | 2000

Thermal Cyclization of 3‐Acyl‐4‐azidopyridines to Isoxazolo[4,3‐c]pyridines

Wolfgang Stadlbauer; Werner Fiala; Michaela Fischer; Gerhard Hojas

4-Azidopyridines such as 3-acetyl-4-azido-2-pyridones 3 or 4-azido-3-ethoxycarbonylpyridine 7 with reactive ortho-acyl substituents were obtained from the 4-hydroxy-2-pyridones 1, resp. 5via 4-tosyloxy-2-pyridones 2 or the 2,4-dichloropyridine 6. DSC-assisted thermolysis of the azides 3 and 7 resulted in electrocyclization and elimination of nitrogen to the isoxazolo[4,3-c]pyridines 4 and 8.


Journal of Heterocyclic Chemistry | 2004

Ring closure reactions of 3-arylhydrazonoalkyl-quinolin-2-ones to 1-aryl-pyrazolo[4,3-c]quinolin-2-ones

Wolfgang Stadlbauer; Gerhard Hojas


Journal of Heterocyclic Chemistry | 2000

Heteroelectrocyclic reaction of 4-azido-3-hydrazonoalkyl-quinolines to 2-arylaminopyrazolo[4,3-c]quinolones†

Gerhard Hojas; Werner Fiala; Wolfgang Stadlbauer


Journal of Heterocyclic Chemistry | 2000

Thermal cyclization of 4-azido-3-nitropyridines to furoxanes†

Wolfgang Stadlbauer; Werner Fiala; Michaela Fischer; Gerhard Hojas


Journal of Heterocyclic Chemistry | 2003

Synthesis of 10-Aryl-10H-naphtho[1,8a,8-fg]indazol-7-ones†‡

Wolfgang Stadlbauer; Gerhard Hojas


ChemInform | 2010

Organic Azides in Heterocyclic Synthesis. Part 27. Heteroelectrocyclic Reaction of 4-Azido-3-hydrazonoalkylquinolines to 2-Arylaminopyrazolo[4,3-c]quinolones.

Gerhard Hojas; Werner Fiala; Wolfgang Stadlbauer


ChemInform | 2004

Organic Azides in Heterocyclic Synthesis. Part 33. Synthesis of 10-Aryl-10H-naphto[1,8a,8-fg]indazol-7-ones.

Wolfgang Stadlbauer; Gerhard Hojas

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