Visible-Light-Mediated Solvent-Switched Photosensitizer-Free Synthesis of Polyfunctionalized Quinolines and Pyridines

Abstract

A solvent (2,2,2-trifluoroethanol (TFE) vs ethyl alcohol (EtOH)) switched synthesis of quinolines and pyridines is illustrated from (E)-2-(1,3-diphenylallylidene)­malononitriles via a Pd­(II)-catalyzed photochemical process. The active catalyst [L2Pd­(0)] generated serves as an exogenous photosensitizer. The process offers predominantly Z-alkenylated quinolines and pyridines in TFE and EtOH, respectively. Furthermore, large-scale synthesis and a few interesting post-synthetic modifications have been demonstrated.

Graphitic carbon nitride materials in dual metallo-photocatalysis: a promising concept in organic synthesis

“…This synthetic protocol possesses broad scope and more than 70 derivatives were synthesized along with late-stage functionalizations of agrochemicals and drugs. In a model reaction 4-bromobenzonitrile (19) was used toward the C(sp 3 )-H bond arylation of N,N-dimethyl acetamide (DMA) (20) as both solvent and C-H precursor. At first the optimization of various reaction parameters was carried out and after that, a library of compounds was synthesized.…”

“…17 Photochemically, a wide range of complex synthetic conversions have been developed in recent years. [18][19][20][21][22][23][24] In contrast to conventional catalysis, photocatalysis exploits the formation of reactive intermediates by photo-induced electron, atom, or energy transfer processes. 25,26 Commonly used photocatalysts (PCs) are mainly conjugated systems that consist of aromatic chromophores, inorganic clusters, organic dyes, and transition metal complexes.…”

Visible-light driven electron–donor–acceptor (EDA) complex-initiated synthesis of thio-functionalized pyridines

“…We have also successfully developed the synthesis of 3-cyanopyridines from γ-ketodinitriles and dicyanodienes under visible light irradiation without using any exogenous photosensitizer [Scheme 1(iii)]. 10…”

“…From our continuous contributions in nitrile-triggered reactions to access various heterocycles 10,13 and taking cues from the previous literature reports, we now envision the synthesis of tetrasubstituted pyridines under metal- and photocatalyst-free conditions. Therefore, herein we disclose a visible-light-induced synthesis of thio-functionalized pyridine from ( E )-2-(1,3-diphenylallylidene)malononitrile ( 1 ) and thiophenol ( a ) via the formation of an electron–donor–acceptor (EDA) complex.…”