[Development of a General Synthetic Method for Organoselenium Compounds Utilizing Copper Catalyzed Cross Coupling and...

Organoselenium compounds have attracted significant interest because of their use as important reagents in organic syntheses and potential biological activities, necessitating the development of simple and general synthetic methods. This article reviews our studies to develop of copper-catalyzed C-Se bond formation reactions via cross coupling and C-H activation. A number of unsymmetrical and symmetrical diaryl selenides were synthesized via Se-arylation of diaryl diselenides or selenium powder with triarylbismuthanes under aerobic conditions, achieving moderate to excellent yields. When the reaction of triphenylbismuthane with elemental Se was monitored with gas chromatography, diphenyl diselenide and diphenyl selenide formation was confirmed. Subsequently, 1-pot 2-step reactions were performed under mild conditions to obtain 3-selanyl imidazo[1,2-a]pyridines from triarylbismuthanes and diimidazopyridyl diselenides, which were generated from imidazo[1,2-a]pyridines and Se powder, in good to excellent yields. It should be noted that all three aryl groups in the bismuth and both selanyl groups in the diaryl diselenide generated from the selenium source were transferred to the coupling products. Cu-catalyzed tandem cyclization of 2-(2-iodophenyl)imidazo[1,2-a]pyridines with selenium for the synthesis of benzo[b]selenophene-fused imidazo[1,2-a]pyridines is also described herein. The molecular structure of the tetracyclic compound features nearly coplanar rings, and the maximum absorption is red-shifted compared to those of imidazo[1,2-a]pyridine and benzoselenophene.