2,2,3,3'-Tetra-phenyl-7,7'-biquinoxaline.

In the crystal structure of the title compound, C(40)H(26)N(4), mol-ecules reside on crystallographic centers of inversion and are linked via C-H⋯N inter-actions about inversion centers into one-dimensional chains: longer C-H⋯π(arene) inter-actions complete the inter-molecular inter-actions.

A novel and highly efficient synthetic route to unsymmetrical organoselenides using cesium bases.

A new and convenient one-pot method for the preparation of unsymmetrical selenides has been developed. In the presence of cesium hydroxide, molecular sieves, and DMF, benzeneselenol undergoes direct alkylation with various alkyl halides for the synthesis of alkyl phenyl selenides in moderate to excellent yields. Another method to prepare unsymmetrical organoselenides was also completed by coupling terminal alkynes with benzeneselenyl bromide. As an application, the synthesis of a selenopeptide was also accomplished. Furthermore, this methodology was extended to the synthesis of an organoselenide on solid support.

Cesium effect: high chemoselectivity in direct N-alkylation of amines.

A novel method for the mono-N-alkylation of primary amines, diamines, and polyamines was developed using cesium bases in order to prepare secondary amines efficiently. A cesium base not only promoted alkylation of primary amines but also suppressed overalkylations of the produced secondary amines. Various amines, alkyl bromides, and alkyl sulfonates were examined, and the results demonstrated this methodology was highly chemoselective to favor mono-N-alkylation over dialkylation. In particular, use of either sterically demanding substrates or amino acid derivatives afforded the secondary amines exclusively, offering wide applications in peptidomimetic syntheses.