The Reaction Of 4-alkyl/acyl-1,4-dihydropyridines Compounds With Benzothiazoles

With the recent developments in visible light-driven photochemistry,1,4-dihydropyridines(1,4-DHPs)have proven to be a useful class of electron donors and proton sources in photoredox catalyzed processes.Therefore,it is not surprising that 1,4-DHPs receive daily increasing interest as synthetic targets.Benzothiazoles especially those 2-substituted ones are widely present in bioactive molecules,and often exhibit effective pharmacological properties.Classical approaches for 2-substituted benzothiazoles mainly relied on the condensation and cyclization strategies employing appropriate reactants.Although such de novo methods might be attractive for manufacturing route development,they are less efficient for medicinal chemists to investigate the structure-activity relationships where timeline concerns are vital.As such,synthetic methods that enabled the selective C2-H functionalization of benzothiazoles could greatly facilitate their applications for medicinal chemistry efforts.State-of-the-art methods are largely limited to transition metal catalysis.The synthesis of acylated 1,4-dihydropyridine was using aryl/alkyl ketones as substrates,ethyl(Z)-3-aminobut-2-enoate as nitrogen source,under I2/DMSO oxidation system.Then using benzothiazoles as substrates,in the presence of BF3·Et2O and Na2S2O8,the benzothiazole derivatives were obtained in good efficiency.All compounds were characterized by ’H NMR,13C NMR,HRMS.This visible light promoted protocol avoided using photocatalysts as well as transition metal catalysts,and proceeded under relatively mild conditions.The wide substrate scope and easy scale-up experimentation allowed expedient preparation of alkylated/acylated benzothiazole derivatives in high efficiency.The scale up synthesis and product derivatization further SET the base for rapidly accessing medicinally relevant benzothiazole derivatives.