title: Reinvestigating the reaction of 1H-pyrazol-5-amines with 4,5-dichloro-1,2,3-dithiazolium chloride: a route to pyrazolo[3,4-c]isothiazoles and pyrazolo[3,4-d]thiazoles.
abstract: The reaction of Appel salt 1 with 1H-pyrazol-5-amines 2 gives main products N-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-1H-pyrazol-5-amines 3, and 6H-pyrazolo[3,4-c]isothiazole-3-carbonitriles 5, together with several minor side products. When the pyrazoles are N-1 methylated, the product ratio 3:5 can be modified by adjusting the pH of the reaction medium: acidic conditions favor formation of the dithiazolylidenes 3, while basic conditions favor formation of pyrazolo[3,4-c]isothiazoles 5. Furthermore, thermolysis of N-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-1H-pyrazol-5-amines 3 gives 1H-pyrazolo[3,4-d]thiazole-5-carbonitriles 4. Single crystal X-ray crystallography supports the structure of 4,6-dimethyl-6H-pyrazolo[3,4-c]isothiazole-3-carbonitrile (5a) and helps resolve a previous incorrect structural assignment of 1H-pyrazolo[3,4-d]thiazole-5-carbonitriles 4.
authors.affiliation: Department of Chemistry, University of Cyprus , P.O. Box 20537, 1678 Nicosia, Cyprus.
authors.forename: Maria
authors.initials: M
authors.lastname: Koyioni
authors.forename: Maria
authors.initials: M
authors.lastname: Manoli
authors.forename: Manolis J
authors.initials: MJ
authors.lastname: Manos
authors.forename: Manos J
authors.initials: MJ
authors.lastname: Manolis
authors.forename: Panayiotis A
authors.initials: PA
authors.lastname: Koutentis
mesh_terms: D015394:Molecular Structure; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry; D013844:Thiazoles / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: C570987:4,5-dichloro-1,2,3-dithiazolium chloride; D011720:Pyrazoles; D013844:Thiazoles