Selective construction of dispiro[indoline-3,2'-quinoline-3',3''-indoline] and dispiro[indoline-3,2'-pyrrole-3',3''-indoline] via three-component reaction

A convenient synthetic procedure for the construction of novel dispirooxindole motifs was successfully developed by base-promoted three-component reaction of ammonium acetate, isatins and in situ-generated 3-isatyl-1,4-dicarbonyl compounds. The piperidine-promoted three-component reaction of ammonium acetate, isatins and the in situ-generated dimedone adducts of 3-ethoxycarbonylmethyleneoxindoles afforded mutlifunctionalized dispiro[indoline-3,2'-quinoline-3',3''-indoline] derivatives in good yields and with high diastereoselectivity. On the other hand, a similar reaction of the dimedone adducts of 3-phenacylideneoxindoles afforded unique dispiro[indoline-3,2'-pyrrole-3',3''-indoline] derivatives with a cyclohexanedione substituent. A plausible reaction mechanism is proposed to explain the formation of the different spirooxindoles.

Switchable C2/C3 positional selectivity of thioisatins in a three-component domino reaction: combined computational and experimental studies

The nucleophile-induced domino reaction is a featured reactivity mode of thioisatin, but the C2/C3 positional selectivity towards a nucleophile has not been understood in-depth. In this work, a domino reaction of thioisatin with bromoacetophenone and tryptamine hydrochloride to produce a benzothiophene-fused eight-membered N-heterocycle was described, showing that the Brønsted acid-base form of the amine partner was crucial for the selectivity, because using tryptamine instead of tryptamine hydrochloride gave a different product. Control experiments and density functional calculations revealed that the domino reaction using tryptamine or tryptamine hydrochloride was triggered by a condensation reaction at the C2 or C3 position of thioisatin, respectively. A delicate balance between local electrophilicity and polarization effect may be responsible for the observed selectivity.