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

Abstract

An interaction of N‐(cyanomethyl)pyridinium salts with vinamidinium perchlorates or enaminones proceeds as a pseudo‐three component process and results in the formation of 3‐ or 2‐substituted pyrido[2,3‐b]indolizine‐10‐carbonitriles, respectively. Optical properties of these compounds have been evaluated, revealing effective green light emission with fluorescence quantum yields of up to 0.81.

Microwave-Assisted Synthesis of Fluorescent Pyrido[2,3-b]indolizines from Alkylpyridinium Salts and Enaminones

“…Based on the previously investigated reaction [ 31 ], we started optimization of the conditions with the use of sodium acetate as base and an iso-propanol/water mixture as solvent ( Table 1 , entries 1–6). Varying the ratio of the starting materials and the base, the target compound 3a was obtained with 50% yield ( Table 1 , entry 5).…”

“…For instance, Opatz et al used 2-alkyl-1-(cyanomethyl)pyridinium salts to prepare aminoindolizines [ 27 ]. Following our interest in the chemistry of cyanomethylpyridinium salts [ 28 , 29 , 30 ], we recently showed that the interaction of N -(cyanomethyl)pyridinium chlorides with enaminones under basic conditions proceeds as a pseudo-three-component reaction, resulting in the formation of pyridoindolizine-10-carbonitriles [ 31 ].…”

Pseudo-multicomponent reactions

“…Festa and Voskressensky 24 reported an efficient synthesis of many 3- and 2-substituted pyrido[2,3- b ]indolizines by a reaction between two equivalents of N -(cyanomethyl)pyridinium ( 38 ) and vinamidinium salts 39 or enaminones 40 . The reaction mechanism showed in the Scheme 5 begins with the base-promoted dimerization of pyridinium salt 41 , which then undergoes an intramolecular cyclization to form the intermediate 42 .…”

Multicomponent synthesis of chromophores – The one-pot approach to functional π-systems

“…Pyridoindolizine are particularly interesting to their biological properties as also indolizines (Sharma and Kumar, 2014;Venugopala et al, 2017). Pyrido[2,3-b]indolizine-10-carbonitriles 42 and 43 are formed by pseudo three-component reactions of N-(cyanomethyl)pyridinium salts with enaminones or vinamidinium perchlorates, respectively (Supplementary Material S9) (Sokolova et al, 2019). The proposed mechanism commences with a basepromoted dimerization of pyridinium salt.…”