Palladium‐Catalysed Synthesis of 9H‐Pyrrolo[1,2‐a]indol‐9‐ones and the Isomeric Indeno[2,1‐b]pyrrol‐8‐ones

Abstract

9H‐Pyrrolo[1,2‐a]indol‐9‐ones and isomeric indeno[2,1‐b]pyrrol‐8‐ones could be obtained in moderate to good isolated yields, by subjecting the same substrates, 2‐bromophenyl N‐tosyl‐2‐pyrrolyl ketones, to different palladium catalysts.

Base‐Mediated N‐Arylation for the Synthesis of 9H‐Pyrrolo[1,2‐a]indol‐9‐ones and 10H‐Indolo[1,2‐a]indol‐10‐ones

“…Fortunately, the desired product 2h could be obtained in 68 % yield of isolated product when 1 mol-% of Pd(PPh 3 ) 4 was added (Scheme 1). [30] While an ortho substituent on the phenyl ring did not affect the product yield significantly (2c vs. 2a), substrates with an α-substituent on the pyrrole ring (1j -1l) resulted in the formation of fluorazones 2j-2l in reduced yields. Finally, the applicability of the current C -N bond formation could also be expanded to indole ketones (1m-1o) to provide 10H-indolo[1,2a]indol-10-ones 2m -2o in moderate to excellent yields of isolated products.…”

“…[24 -36] Among these, the most proven method is the intramolecular Friedel-Crafts acylation and variants onto the pyrrole moiety. [24 -28] Other practical methods include the transition-metal-catalyzed intramolecular N-arylation [30,31] and cyclocarbonylation reactions. [32 -34] Recently, we have become interested in base-mediated CÀ N and CÀ O bond formation for the synthesis of heterocyclic compounds.…”

Synthesis of Heteroarene‐Fused Cyclopentadienes and Related Compounds Suitable for Metallocene Preparation

“…[38,50,158] A two-stage method for the synthesis of indeno[2,1-b]pyrrol-8-ones 205-209 involved the acylation of N-tosylpyrroles by 2bromoaryl carboxylic acids followed by Pd-catalyzed cyclization (Scheme 33B). [159,160] The reduction of these compounds to pyrrole-fused indenes was not studied.…”

“…Synthesis of 1,8-dihydroindeno[2,1-b]pyrrole derivatives. [38,50,[158][159][160] Scheme 34. Synthesis of 8H-indeno[2,1-b]furan-8-ones.…”

Unconventional [2 + 3] Cyclization Involving [1,4]-Sulfonyl Transfer to Construct Polysubstituted Fluorazones as Inhibitors of Indoleamine 2,3-Dioxygenase 1

“…However, compared with well-developed 9 H -pyrrolo­[1,2- a ]­indoles, fewer synthetic routes have been developed to generate 9 H -pyrrolo­[1,2- a ]­indol-9-ones . These approaches include intramolecular ring closure, cross-coupling, and cyclocarbonylation. , For example, Lei’s group developed in 2017 a Pd/Cu-catalyzed oxidative dual C–H bond carbonylation process to access fluorazones from N -arylpyrroles and CO . In 2018, Mátravölgyi reported intramolecular cyclization of amidopyrroles to afford the corresponding fluorazones .…”