[3+2]‐Cycloaddition of Catalytically Generated Pyridinium Ylide: A General Access to Indolizine Derivatives

Abstract

Pyridinium ylide is a versatile building block in synthetic organic chemistry, especially in the synthesis of N‐heterocycles. In this minireview, we have summarized the advances of [3+2]‐cycloaddition of catalytically generated pyridinium ylide for the synthesis of indolizines (since 1970s). Accordingly, the ylide discussed in this article is generated in situ from carbene precursors and N‐heteroarenes under catalytic conditions, including photocatalysis/thermocatalysis, and metal‐catalysis. The metal‐catalyzed version is the main focus, which is classified and summarized based on the type of dipolarophiles, alkyne and alkene, each class is further subdivided according to the metal catalysts used in these reactions. The analogous [3+2]‐cycloaddition of vinyl metal carbene with pyridines, the formation of pyridinium ylide with other type of carbene precursors or with different N‐heteroarenes, have been also included herein separately.

Heterocyclic group transfer reactions with I(iii) N-HVI reagents: access to N-alkyl(heteroaryl)onium salts via olefin aminolactonization

“…In organic chemistry, they serve as ionic liquids 5 (2) and phase transfer catalysts, 6 exhibit a diverse range of biological activities (3, 4), and have a long history as synthetic intermediates, an area that has seen a recent surge of new advancements. Representative of their versatile reactivity, pyridinium and related salts can undergo full or partial reductions, [7][8][9] cycloadditions, 10,11 photochemical isomerizations, 12 cross couplings, 13 addition of one-or two-electron heteroatom or carbon nucleophiles, 8,14 and facile C-H metalations, 15 and many of these include asymmetric variants [16][17][18] (Fig. 1).…”

Recent Developments in the Cyclization of Alkynes and Nitrogen Compounds for the Synthesis of Indole Derivatives

“…[5] Indoles have been studied for over one hundred years and these studies delivered to the scientific community impressive advances in biological properties [6] and synthetic applications of this class of compounds. [7] Although less studied, its derivatives azaindole, [8] carbazole, [9] carboline, [10] indazole, [11] 3H-indole, [12] indoline, [13] indolizine, [14] isoindole, [15] and isoindoline [16] have gained prominence in organic synthesis, medicinal chemistry, materials science, and industry. Because of such an application, the synthesis of indole derivatives has been a subject of several approaches.…”

Access to 6-hydroxy indolizines and related imidazo[1,5-a]pyridines through the SN2 substitution/condensation/tautomerization cascade process

“…[6][7][8][9][10][11] As a consequence, much effort has been devoted to their synthesis and functionalization, and thus many methods have been developed. [12][13][14] In addition to classical Scholtz or Tschichibabin reactions, a variety of straightforward and efficient methods have been reported in recent years 15-20 including 1,3-dipolar cycloaddition of pyridinium salts and intramolecular cyclization catalyzed by transition metals and intermolecular cyclization. Despite the efficiency of these methods, they suffer from the requirement of specic preorganized substrates, necessity of expensive metal catalysts, multistep synthesis, and a lack of product diversity.…”