The conversion of isothiazoles into pyrazoles using hydrazine
摘要:
The conversion of isothiazoles into pyrazoles on treatment with hydrazine is investigated. The influence of various C-3, C-4 and C-5 isothiazole substituents and some limitations of this ring transformation are examined. When the isothiazole C-3 substituent is a good nucleofuge, 3-aminopyrazoles are obtained. However, when the 3-substituent is not a leaving group it is retained in the pyrazole product. Treatment of 4-bromo-3-chloro-5-phenylisothiazoie 56 or 3-chloro-4,5-diphenylisothiazole 57 with anhydrous hydrazine at ca. 200 degrees C for a few minutes gives the corresponding 3-hydrazinoisothiazoles 61 and 64 respectively in high yields; the stability of these new hydrazines is investigated. 5,5'-Diphenyl-3,3'-biisothiazole-4,4'-dicarbonitrile 78 reacts with hydrazine to give 5,5'-diphenyl-3,3'-bi(1H-pyi-azole)-4,4'-dicarbonitrile 79. Methylhydrazine reacts with 3-chloro-5-phenytisothiazole-4-carbonitrile 1 to give 3-(1-methylhydrazino)-5-phenylisothiazole-4-carbontrile 83 and 3-amino-lmethyl-5-phenylpyrazole-4-carbonitrile 84. All products are fully characterised and rational mechanisms for the isothiazole into pyrazole transformation are proposed. (C) 2009 Elsevier Ltd. All rights reserved.
Synthesis and antiviral activity of a new series of 4-isothiazolecarbonitriles
摘要:
A series of 4-isothiazolecarbonitriles was synthesized and screened for in vitro antiviral activity. The effect of various substituents on the phenyl ring, as well as the substitution of the phenyl for other aromatic and heteroaromatic rings, was examined to establish the requirements for optimum activity. The most active member of the series, 3-methylthio-5-phenyl-4-isothiazolecarbonitrile, exhibited a high level of activity against enteroviruses polio 1 and ECHO 9. Preliminary studies on its mechanism of action indicated that this compound had an effect on an early event in the replication of poliovirus type 1. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
Regiospecific Suzuki coupling of 3,5-dichloroisothiazole-4-carbonitrile
作者:Irene C. Christoforou、Panayiotis A. Koutentis、Charles W. Rees
DOI:10.1039/b306005e
日期:——
3,5-Dichloroisothiazole-4-carbonitrile 1 reacts with aryl- and methylboronic acids to give in high yields the 3-chloro-5-(aryl and methyl)-isothiazole-4-carbonitrile 2 regiospecifically. The reaction was optimized with respect to base, phase transfer agent and palladium catalyst. Suzuki coupling at C-5 was also achieved in high yield using potassium phenyltrifluoroborate. The regiospecificity of either coupling method is maintained with 3,5-dibromoisothiazole-4-carbonitrile 4 to give exclusively 3-bromo-5-phenylisothiazole-4-carbonitrile 5. Suzuki cross-coupling conditions applied to 3-chloro-5-phenylisothiazole-4-carbonitrile 2a gave 3-phenoxy-5-phenylisothiazole-4-carbonitrile 6, which was prepared independently, and not the 3-phenyl derivative. All isothiazole products were fully characterized.
Synthesis and antiviral activity of a new series of 4-isothiazolecarbonitriles
作者:Christian C.C. Cutrí、Adriana Garozzo、Maria A. Siracusa、Maria C. Sarvá、Gianna Tempera、Ernesto Geremia、Maria R. Pinizzotto、Francesco Guerrera
DOI:10.1016/s0968-0896(98)80007-2
日期:1998.12
A series of 4-isothiazolecarbonitriles was synthesized and screened for in vitro antiviral activity. The effect of various substituents on the phenyl ring, as well as the substitution of the phenyl for other aromatic and heteroaromatic rings, was examined to establish the requirements for optimum activity. The most active member of the series, 3-methylthio-5-phenyl-4-isothiazolecarbonitrile, exhibited a high level of activity against enteroviruses polio 1 and ECHO 9. Preliminary studies on its mechanism of action indicated that this compound had an effect on an early event in the replication of poliovirus type 1. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
The conversion of isothiazoles into pyrazoles using hydrazine
作者:Heraklidia A. Ioannidou、Panayiotis A. Koutentis
DOI:10.1016/j.tet.2009.06.041
日期:2009.8
The conversion of isothiazoles into pyrazoles on treatment with hydrazine is investigated. The influence of various C-3, C-4 and C-5 isothiazole substituents and some limitations of this ring transformation are examined. When the isothiazole C-3 substituent is a good nucleofuge, 3-aminopyrazoles are obtained. However, when the 3-substituent is not a leaving group it is retained in the pyrazole product. Treatment of 4-bromo-3-chloro-5-phenylisothiazoie 56 or 3-chloro-4,5-diphenylisothiazole 57 with anhydrous hydrazine at ca. 200 degrees C for a few minutes gives the corresponding 3-hydrazinoisothiazoles 61 and 64 respectively in high yields; the stability of these new hydrazines is investigated. 5,5'-Diphenyl-3,3'-biisothiazole-4,4'-dicarbonitrile 78 reacts with hydrazine to give 5,5'-diphenyl-3,3'-bi(1H-pyi-azole)-4,4'-dicarbonitrile 79. Methylhydrazine reacts with 3-chloro-5-phenytisothiazole-4-carbonitrile 1 to give 3-(1-methylhydrazino)-5-phenylisothiazole-4-carbontrile 83 and 3-amino-lmethyl-5-phenylpyrazole-4-carbonitrile 84. All products are fully characterised and rational mechanisms for the isothiazole into pyrazole transformation are proposed. (C) 2009 Elsevier Ltd. All rights reserved.