This study describes the syntheses of 2,3-bis­(selanyl)­quinoxalines via the photoinduced cyclizations of o-diisocyanoarenes with diaryl or dialkyl diselenides, in addition to providing a detailed discussion of the corresponding mechanism and revealing that the developed procedure can also be applied to prepare 2-thiolated quinoxaline derivatives from o-diisocyanoarenes and thiols. The developed technique does not need the use of additives or metal catalysts and features the advantages of a high conversion, a broad substrate scope, and mild reaction conditions, thereby rendering it a valuable addition to the quinoxaline synthesis toolbox.

The photoinduced reactions of tetraphenyldiphosphine disulfide with a range of organic dichalcogenides successfully afforded a series of phosphorus(V)−chalcogen interelement compounds via a radical process. The relative reactivities of the organic dichalcogenides (i.e., (PhS) 2 , (PhSe) 2 , and (PhTe) 2 ) toward the P III or P V groups in the diphosphine analogues under light were investigated in detail, and a convenient method was developed to form P−S or P−Se interelement compounds from tetraphenyldiphosphine disulfide and (PhS) 2 or (PhSe) 2 upon photoirradiation. Furthermore, the relative photochemical properties and reactivities of tetraphenyldiphophine (P− P interelement compound) and its analogues toward photoinduced radical addition reactions were also discussed. The formed P−E (E = S, Se) interelement compounds could be utilized for ionic reactions, and they could be transformed into various phosphine reagents via one-pot processes.

Using tetraaryllead compounds (PbAr4) as arylating reagents, isocyanides undergo selective diarylation in the presence of palladium catalysts such as Pd­(OAc)2 or Pd­(PPh3)4 to afford imines and/or α-diimines based on the isocyanide employed. With aliphatic isocyanides, imines are obtained preferentially, whereas α-diimines are formed in the case of electron-rich aromatic isocyanides. The differences in imine/α-diimine selectivity can be attributed to the stability of imidoylpalladium intermediates formed in this catalytic reaction. Compared with other arylating reagents, tetraaryllead compounds are excellent candidates for use in the selective transformations to imines and/or α-diimines, especially in terms of inhibiting the oligomerization of isocyanides, which results in a lower product selectivity in many transition-metal-catalyzed reactions of isocyanides.

In this study, the reactivity of organochalcogen compounds toward a representative alkyl-lead bond compound under light was investigated in detail. Under light irradiation, the Cy-Pb bond of Cy6Pb2 (Cy = cyclohexyl) undergoes homolytic cleavage to generate a cyclohexyl radical (Cy•). This radical can be successfully captured by diphenyl diselenide, which exhibits excellent carbon-radical-capturing ability. In the case of (PhS)2 and (PhTe)2, the yields of the corresponding cyclohexyl sulfides and tellurides were lower than that of (PhSe)2. This probably occurred due to the low carbon-radical-capturing ability of (PhS)2 and the high photosensitivity of the cyclohexyl-tellurium bond.

The transition-metal-catalyzed diarylation of isocyanides with triarylbismuthines was investigated in detail, and rhodium catalysts such as [RhCl(nbd)]2 were found to selectively afford N-alkyl diaryl ketimines. On the other hand, palladium-catalyzed diarylation proceeded with the incorporation of two molecules of isocyanide, preferentially yielding N,N’-dialkyl or N,N’-diaryl α-diimines. In addition, a cascade synthesis of 2,3-diarylquinoxalines starting from the palladium-catalyzed diarylation of isocyanides with triarylbismuthines was successfully achieved.