Cascade synthesis of selective dihydro pyridazino fused acridinone derivatives via MCM-41 catalyzed ring-opening/ring-closure reaction

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.

Engaging Isatins in Multicomponent Reactions (MCRs) - Easy Access to Structural Diversity

Multicomponent reactions (MCRs) are a valuable tool in diversity-oriented synthesis. Its application to privileged structures is gaining relevance in the fields of organic and medicinal chemistry. Isatin, due to its unique reactivity, can undergo different MCRs, affording multiple interesting scaffolds, namely oxindole-derivatives (including spirooxindoles, bis-oxindoles and 3,3-disubstituted oxindoles) and even, under certain conditions, ring-opening reactions occur that leads to other heterocyclic compounds. Over the past few years, new methodologies have been described for the application of this important and easily available starting material in MCRs. In this review, we explore these novelties, displaying them according to the structure of the final products obtained.

Recent advances in cyclization reactions of isatins or thioisatins via C–N or C–S bond cleavage

This review summarizes recent developments on cyclization reactions induced by the C–N or C–S bond cleavage of isatins or thioisatins in the last 5 years, which produce fused products instead of spiro compounds.