Synthesis and characterization of novel substituted pyrrole, thiophene and furans

Abstract

Sixteen new compounds, including novel five-membered heterocyclic systems (pyrrole, thiophene, or furan) linked to imidazole, thiazole, or quinoline rings are reported. The intermediate 1,4-diketones were synthesized via the Stetter reaction in the presence of thiazolium salt as a catalyst. Cyclization reactions of the 1,4-dicarbonyl compounds with polyphosphoric acid, ammonium acetate or Lawesson's reagent by the Paal-Knorr synthesis, afforded unknown 2,5-disubstituted furan, pyrrole, or thiophene compounds in moderate yields, respectively. The structures of the synthesized compounds were confirmed by IR, 1 H NMR, 13 C NMR, and elemental analysis.

Theoretical Study on the Effect of Annelation and Carbonylation on the Electronic and Ligand Properties of N-Heterocyclic Silylenes and Germylenes: Carbene Comparisons begin To Break Down

“…However, annelation by furan and thiophene has similar effects as annelation with benzene. The electrophilicity increases in the order 16 < 17 < 18 , which is in agreement with the relative inductive electron-withdrawing ability of these heterocycles …”

Tuning the Electronic and Ligand Properties of Remote Carbenes: A Theoretical Study

“…There is no appreciable change in the ligand properties of the parent rNHC 19 as a result of annulation with the electron-rich pyrrole molecule. The π-accepting abilities increases in the order 32 < 33 < 34 , which is in agreement with the relative inductive electron-withdrawing abilities of these heterocycles . Among all of the six-membered rNHCs, 34 was found to have the highest π acidity.…”

Novel 1,2,4-Triazolo[1,5-a]pyridines and Their Fused Ring Systems Attenuate Oxidative Stress and Prolong Lifespan of Caenorhabiditis elegans

“…Isoxazoles constitute an important family of five-membered hetrocycles in view of their use in many natural products syntheses , and occurrence in pharmaceutical agents such as COX-2 inhibitor Bextra . The pyrrole skeleton is of great importance to chemists as well as biologists, as it is found naturally in plants and in animal cell constituents . Pyrazole derivatives are synthetic targets of utmost importance in the pharmaceutical industry because the pyrazole ring has been known as an important framework in a large number of drugs. − Moreover, recent reports display the pyrazole chemotype as the structural motif of a number of highly potent inhibitors of coagulation factor Xa and antitumor CDK …”