Recent methods for the synthesis of indolizines (microreview)

Base-promoted [4 + 2] annulation of pyrrole-2-carbaldehyde derivatives with β,γ-unsaturated α-ketoesters: syntheses of 5,6-dihydroindolizines

“…Based on the experimental results and the previous literature 4,10,11 a plausible reaction mechanism for this [4 + 2] annulation was proposed as shown in Scheme 4. Initially, promoted by the base, 1a would be deprotonated to form intermediate A .…”

“…These annulation processes are similar and involve cyclocondensation, cycloaddition, cyclization/elimination, and cycloisomerization reactions. 11 With the development of metal catalysis, chemists have also developed strategies for building indolizines using metal complexes. 12…”

Highly Fluorescent Pyrido[2,3‐b]indolizine‐10‐Carbonitriles through Pseudo Three‐Component Reactions of N‐(Cyanomethyl)pyridinium Salts

“…[14,15] Employing these tools for the preparation of fluorophores and electrophores emerged as a useful technique, [16][17][18][19] enabling fast creation of numerous scaffolds with diverse structure and needful properties. Indolizines are indeed sought-for heterocycles, [20,21] which have various applications as biologically active compounds, [22][23][24][25] dyes, [26][27][28] molecular probes and sensors. [29][30][31][32][33] They are also well-known fluorophores, [34] with some recent examples of multicomponent syntheses.…”

“…Domino and multicomponent reactions allow rapid and efficient construction of molecular complexity; they are widely used for the synthesis of natural products and analogues,, pharmaceutical substances, functional materials,, macrocyclizations, Employing these tools for the preparation of fluorophores and electrophores emerged as a useful technique, enabling fast creation of numerous scaffolds with diverse structure and needful properties. Indolizines are indeed sought‐for heterocycles,, which have various applications as biologically active compounds, dyes, molecular probes and sensors . They are also well‐known fluorophores, with some recent examples of multicomponent syntheses .…”

Synthesis of a crystallochromic indolizine dye by a base- and catalyst-free photochemical route

“…2 In addition, indolizines usually exhibit favorable fluorescent and photophysical properties and may be applied as functional dyes, 3 fluorescent probes 4 or organic light-emitting diodes (OLED). 5 As a result, the development of new synthetic strategies toward indolizine derivatives with defined substitution patterns has become a challenging and appealing research topic, 6 leading to synthetic approaches such as the generally applicable 1,3-dipolar cycloaddition between N-alkylpyridinium ylides and dipolarophiles, 7 oxidative cyclization, 8 cross coupling, 9 transition-metal catalysis, 10 cycloisomerization reactions, 11 along with a variety of specific reactions. 12 Notably, photochemical syntheses of indolizines are rather rare despite the obvious benefits and advantages of light as controllable and traceless reagent.…”