title: Non-classical transformation of benzendiazonium hydrogen sulfates. Access to 1,3-dimethylisochromeno[4,3-c]pyrazol-5(1H)-one, a potential benzodiazepine receptor ligand.
abstract: The compound 2-((1,3-dimethyl-1H-pyrazol-5-yl)(methyl)carbamoyl)benzene-diazonium hydrogen sulfate (10) was reacted with copper sulfate and sodium chloride, in the presence of ascorbic acid as reducing agent, to afford a mixture of the chlorinated epimers 4'-chloro-2,2',5'-trimethyl-2',4'-dihydrospiro[isoindoline-1,3'-pyrazol]-3-one (18) and (19), the epimers 4'-hydroxy-2,2',5'-trimethyl-2',4'-dihydrospiro[isoindoline-1,3'-pyrazol]-3-one (20) and (21), and N-(1,3-dimethyl-1H-pyrazol-5-yl)benzamide (22). Under the foregoing conditions, diazonium salt 10 affords neither the 2-chloro-N-(1,3-dimethyl-1H-pyrazol-5-yl)-N-methylbenzamide (23) nor the tricyclic derivative 24, the classical products of the Sandmeyer and Pschorr reactions, respectively. Finally, by heating 20 at 210 °C the compound 1,3-dimethylisochromeno[4,3-c]pyrazol-5(1H)-one (24) was obtained. The transformation under the above conditions of 2-((4-chloro-3-methyl-1-phenyl- 1H-pyrazol-5-yl)(methyl)carbamoyl)benzendiazonium hydrogen sulphate (11) afforded 4',4'-dichloro-2,5'-dimethyl-2'-phenyl-2',4'-dihydrospiro[isoindoline-1,3'-pyrazol]-3-one (29) as the sole reaction product.
authors.affiliation: Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche, Università degli Studi di Palermo, Via Archirafi, 32, 90123-Palermo, Italy. demetrio.raffa@unipa.it.
authors.forename: Benedetta
authors.initials: B
authors.lastname: Maggio
authors.forename: Demetrio
authors.initials: D
authors.lastname: Raffa
authors.forename: Maria Valeria
authors.initials: MV
authors.lastname: Raimondi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Daidone
mesh_terms: D003460:Crystallization; D003979:Diazonium Compounds / Q000737:chemistry*; D018682:GABA Agents / Q000138:chemical synthesis*; D049934:Isocoumarins / Q000138:chemical synthesis*; D008024:Ligands; D011720:Pyrazoles / Q000138:chemical synthesis*; D011963:Receptors, GABA-A / Q000378:metabolism*; D013463:Sulfuric Acid Esters / Q000737:chemistry*
chemical_list: D003979:Diazonium Compounds; D018682:GABA Agents; D049934:Isocoumarins; D008024:Ligands; D011720:Pyrazoles; D011963:Receptors, GABA-A; D013463:Sulfuric Acid Esters