Maria Krawczyk

Reactions of nitroxides. Part X: Antifungal activity of selected sulfur and selenium derivatives of 2,2,6,6-tetramethylpiperidine☆

The antifungal activity of nitroxyl radicals-derivatives of 2,2,6,6-tetramethylpiperidine-1-oxyl with reactive substituents 4-isothiocyanato-, 4-isocyano-, and 4-isoselenocyanato- and of N-formyl-, N-thioformyl-, N-selenoformyl-derivatives of 2,2,6,6-tetramethylpiperidine was investigated. Those of the above compounds, which contain a sulfur or selenium atom are the most active against four fungus plant patogens: Botrytiscinerea, Fusariumculmorum, Phytophthoracactorum, Rhizoctoniasolani. 4-Isoselenocyanato-2,2,6,6-tetramethylpiperidine-1-oxyl proved to be the most active compound.

Synthesis and Pesticidal Properties of Thio and Seleno Analogs of Some Common Urea Herbicides

Thio and seleno analogs of fenuron, isoproturon, chlorotoluron, metoxuron, monuron, and diuron were synthesized from the corresponding aryl amines. Their reaction with thiophosgene leads to isothiocyanates. Aryl amines were also converted (via isocyanides) to isoselenocyanates. The reaction of both isothio- and isoselenocyanates with dimethylamine affords the corresponding thio and seleno analogs of the above-mentioned urea herbicides. Herbicidal activity of the synthesized compounds was slightly lower than the activity of the parent urea herbicides. The thio and seleno analogs as well as the parent ureas showed good fungicidal activity at a concentration of 200 ppm against selected fungi.

Reactions of nitroxides XIV. Analogs of phenoxy carboxylic herbicides based on the piperidine scaffold; unexpected fungicidal activity of the 2-[(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)oxy]butanoic acid

Abstract Alkanoic acid derivatives bearing a nitroxyl moiety 3a–e were synthesized from 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (1) and the corresponding 2-bromoalkane carboxylic acids 2a–e. The herbicidal and antifungal activity of 3a–e was tested. No herbicidal activity of the tested compounds was found. The 2-[(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)oxy]butanoic acid 3c revealed a strong antifungal activity against the pathogenic fungus Phytophthora cactorum.

Synthesis and fungicidal activity of 2-methylalkyl isonicotinates and nicotinates

Homologs and analogs of 2-methylheptyl isonicotinate (new, natural antifungal and antibacterial antibiotic isolated from Streptomyces sp. 201): racemic 2-methylalkyl isonicotinates 4 and nicotinates 5 and enantiomerically enriched in the R and S isomers, 2-methylpentyl isonicotinate and nicotinate were obtained. Fungistatic activity of the compounds was evaluated. Nicotinates 5a–c show significant activity against phytopathogenic fungi: Fusarium culmorum, Phytophthora cactorum, Rhizoctonia solani. The activity of the enantiomerically enriched compounds was comparable to the activity of racemic ones. There was no significant difference in fungistatic activity between the enantiomerically enriched R and S isomers. Investigated compounds and their oxalates have proven to be active against chalkbrood disease caused by fungal species Ascosphaera apis. The activity of the nicotinates 5a and 5b and oxalates 5a–c against Ascosphaera apis was higher than the activity of oxalic acid itself. Especially high activity was shown for 2-methylbutyl nicotinate 5a and oxalate of 2-methylpentyl nicotinate 5b.Graphical abstract

Reactions of nitroxides 16. First nitroxides containing tellurium atom

2-Chloroethylamine hydrochloride and 3-chloropropylamine hydrochloride were converted with diphenyl ditelluride and sodium borohydride to primary amines containing the tellurium atom. Reaction of tellurium amines with thiophosgene gave the corresponding isothiocyanates, which in turn were transformed with nitroxyl amines to thioureas bearing both a nitroxyl moiety and a tellurium atom. Fungicidal activity of tellurium nitroxides was tested. 1-(2,2,6,6-Tetramethyl-1-oxyl-4-piperidinyl)-3-(3-(phenyltellanyl)propyl) thiourea showed high fungistatic activity against Fusarium culmorum and Phytophtora cactorum.

Reactions of Nitroxides. Part XII (1). - 2,2,6,6-Tetramethyl-1-oxyl- 4-piperidyl Chloroformate - A New Reactive Nitroxyl Radical. A One-pot Synthesis of 2,2,6,6-Tetramethyl-1-oxyl-4-piperidyl N,N-Dialkyl-carbamates

The reactive nitroxides 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl chloroformate and 2,2,6,6-tetramethyl- 1-oxyl-4-piperidyl chlorothionoformate were synthesized from 2,2,6,6-tetramethyl-4-hydroxypiperidin- 1-oxyl and diphosgene (68%) or thiophosgene (61%), respectively. The reactions of the chloroformate and chlorothionoformate with lower secondary amines lead to 2,2,6,6-tetramethyl- 1-oxyl-4-piperidyl N,N-dialkylcarbamates (59 - 94%) and thionocarbamates (35 - 65%), respectively. Unexpectedly, the same 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl N,N-dialkylcarbamates were obtained directly in a one-pot reaction of 2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxyl with diphosgene and lower tertiary alkylamines by dealkylation in 32 - 86% yield. The antifungal activity of the synthesized carbamates and thionocarbamates has been demonstrated Graphical Abstract Reactions of Nitroxides. Part XII [1]. – 2,2,6,6-Tetramethyl-1-oxyl- 4-piperidyl Chloroformate – A New Reactive Nitroxyl Radical. A One-pot Synthesis of 2,2,6,6-Tetramethyl-1-oxyl-4-piperidyl N,N-Dialkyl-carbamates