Synthesis of ring-fused pyrroles. I. 1,3-Dipolar cycloaddition reactions of munchnone derivatives obtained from tetrahydro-.beta.-carboline-3- and -1-carboxylic acids

Abstract

The reaction of various tetrahydro-0-carboline-3-carboxylic acids, 2a-c, with dimethyl acetylenedicarboxylate in acetic anhydride directly afforded the corresponding indolizino [6,7-6] indoles 4a-c, in moderate yields. Likewise, treatment of 1,2,3,4-tetrahydro-/3-carboline-1-carboxylic acid, 5, in acetic anhydride, with a variety of acetylenic dipolarophiles and less successfully with olefinic dipolarophiles furnished the corresponding indolizino-[8,7-b]indole derivatives. These reactions involve a 1,3-dipolar cycloaddition of the respective munchnone intermediates (3 and 6), respectively, formed in situ, with the dipolarophilic substrates.Huisgen and coworkers have recently reported a general synthesis of pyrroles1 and pyrrolines2 using mesoionic A2-oxazolium-5-olates (munchnones). These reactions involved a 1,3-dipolar cycloaddition of the munchnone, behaving like a cyclic azomethine ylide,3 to the corresponding acetylenic or olefinic dipolarophile, followed by C02 evolution, and aromatization or tautomerization.4 5678Most examples of the application of this reaction, to date, have involved the use of acyclic, JV-acyl -amino acids as the starting material,5-8 although Huisgen has converted L-proline to the pyrrolizine derivative, 1, in 76% yield by reaction with dimethyl acetylenedicarboxylate in acetic anhydride.1

Acid-Catalyzed Multicomponent Tandem Cyclizations: Access to Polyfunctional Dihydroindolizino[8,7-b]indoles

“…Owing to the importance and usefulness of dihydro­indolizino­[8,7- b ]­indole derivatives, various approaches for their construction have been developed. − The general strategy differs, depending on how the pyrrole ring is constructed. For example, Knölker and co-workers reported a two-step procedure for the construction of the pyrrole ring by addition of a propargyl Grignard reagent to 3,4-dihydro-β-carboline and subsequent silver­(I)-promoted oxidative cyclization (Scheme a) .…”

Acid‐Catalyzed Four‐Component Tandem Double Cyclization: Access to Dihydroindolizino[8,7‐b]indoles

“…Due to the significant advancements made to develop step‐economic strategies toward fused heterocyclic frameworks, especially those containing privileged moieties, alternative, rapid, and versatile approaches to assemble fused pyrrole ring are still needed …”

“…[2] Due to the significant advancements made to develop step-economic strategies toward fused heterocyclic frameworks, especially those containing privileged moieties, alternative, rapid, and versatile approaches to assemble fused pyrrole ring are still needed. [3][4][5][6][7][8][9][10] An-Xin Wu and co-worker developed two strategies for the synthesis of pyrrole ring by Knoevenagel condensation and oxidative aromatization reaction. (Scheme 1a).…”

Allylic Amination andN-Arylation-Based Domino Reactions Providing Rapid Three-Component Strategies to Fused Pyrroles with Different Substituted Patterns

“…In the past several decades, many methodologies for the synthesis of fused pyrroles have been developed, which involved rearrangement-cyclization of alkynol, 2a alkynyl ketones, 2b cycloketone annulations 3 , metal-catalyzed cascade cyclization of alkynes, 4 and 1,3-dipolar cycloadditions of mühnone derivatives. 5 The development of new alternate and more efficient strategies to this family of heterocyclic compounds, minimizing the formation of waste and by-products, continues to be of great interest and challenging. To the best of our knowledge, a one-pot multicomponent synthesis of fused pyrroles via metal-free domino reaction involving intermolecular allylic amination has not been well documented yet.…”