The compound 2-((1,3-dimethyl-1
H-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),
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The compound 2-((1,3-dimethyl-1
H-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-1
H-pyrazol-5-yl)benzamide (
22). Under the foregoing conditions, diazonium salt
10 affords neither the 2-chloro-
N-(1,3-dimethyl-1
H-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(1
H)-one (
24) was obtained. The transformation under the above conditions of 2-((4-chloro-3-methyl-1-phenyl- 1
H-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.
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