Synthesis and reactions of 1-hydroxy-9,9a-dihydro-1H-imidazo[1,2-a]indol-2-(3H)-ones

Transition-Metal-Free Stereospecific Oxidative Annulative Coupling of Indolines with Aziridines

“…Among them, imidazoindolines represent privileged structures due to their interesting biological properties. 4 Stereospecific syntheses of these fused structural frameworks in an atom-and step-economical approach 5 would thus be valuable. While small ring heterocycles, due to their staple architecture and intrinsic ring strain, have a propensity to undergo easy ring scissoring, and are thereby useful for the construction of diverse heterocycles.…”

“…12 The latter can oxidize using DDQ to furnish 3, which can undergo an electrophilic chlorination using NaOCl 9 to give the iminium ion b that can lead to an intramolecular cyclization to furnish c. Base promoted dehydrochlorination of c can furnish the target heterocycle 4, which can be reduced using NaBH 3 CN to yield imidazoindolines that are privileged structural scaffolds with a broad bioactive spectrum. 4 Scheme S2a presents some postsynthetic applications for C−C coupling of 4 with organoboranes. The Pd-catalyzed Suzuki-coupling of 4ea with 1-pyreneboronic acid produced 5 in 85% yield, while the borylation employing B 2 pin 2 gave 6 in 73% yield.…”

“…In this realm, C–H functionalization of indoles has witnessed impeccable growth, owing to the profuse prominence of the indole frameworks in a myriad of bioactive molecules. Among them, imidazoindolines represent privileged structures due to their interesting biological properties . Stereospecific syntheses of these fused structural frameworks in an atom- and step-economical approach would thus be valuable.…”

Synthesis of Imidazo[1,2-a]Indoles from 2-Chloroindole-3-Carbaldehyde

“…The first synthesis involved the isolation of aldehyde 5 in only 7% yield. 5 Other related compounds with hydrogenated indole moiety, such as compounds 6, 7 and their derivatives 6,7 have been synthesized later (Fig. 2).…”