Condensation of isatin with diketones

Spiro[4H–pyran‐3,3′‐oxindoles] Derived from 9,10‐dihydroacridine

“…Our work here continues our studies on the spiro‐forming abilities of isatins, based on the reactive ketone group, be they bicyclic (other work ), or in our work using tricycle 3 and now tetracycle 7 . Many further possibilities exist for the exploitation of isatins, including compound 7 , on which we plan to report in the future.…”

“…The first report of the reaction of an isatin with a cyclohexane‐1,3‐dione generating a spiro[4 H –pyran‐3,3′‐oxindole] dates back to 1929 . Since then, the multistep process has been re‐examined several times , and in one instance , acyclic 1,3‐diketones were employed successfully. 1,3‐Keto‐esters have also been used as the 1,3‐dicarbonyl component .…”

Spiro[4H‐pyran‐3,3′‐oxindoles] Derived from 1,2,3,4‐tetrahydroquinoline—Part 2

“…The first report of the reaction of an isatin with a cyclohexane‐1,3‐dione generating a spiro[4 H ‐pyran‐3,3′‐oxindole], dates back to 1929 . Since then, the multistep process has been re‐examined several times , and in one instance , acyclic 1,3‐diketones were employed successfully. An attempt to use barbituric acid instead of a carbocyclic 1,3‐dicarbonyl compound failed to produce a spiro‐product .…”

Synthesis of spiro[dihydropyridine-oxindoles] via three-component reaction of arylamine, isatin and cyclopentane-1,3-dione

“…A literature survey showed that even though there are a lot of reports about the condensation of isatins with cyclic 1,3-dicarbonyl compounds [30–33], the condensation reaction of isatin with cyclopentane-1,3-dione seemed still not to have been investigated and the 3,3-bis(2-hydroxy-5-oxo-cyclopent-1-enyl)oxindoles 3a – 3d have not been prepared until now. Thus, the direct condensation of isatins with two molar cyclopentane-1,3-dione was carried out in acetic acid and the desired condensation products 3a – 3d were obtained in high yields (Scheme 2).…”