Elemental sulfur‐promoted cyclization for the one‐pot synthesis of tetra‐substituted imidazoles from benzylamines and ketones is described. Elemental sulfur combined with molecular oxygen as the benign co‐oxidant was found to be the key for the high efficiency of this transformation under metal‐free conditions. A range of tetrasubstituted imidazoles were synthesized from simple ketones and amines with good functional group tolerance.magnified image

Aerobic cyclization of 2-aminobenzothiazoles and cyclic ketones enabled by the combination of elemental sulfur and oxygen under metal-free conditions.

Herein, the first elemental sulfur-promoted aerobic dehydrogenative aromatization of cyclohexanones is described that provides novel access to synthetically useful o-arylenediamines. This protocol complements previous palladium- and iodine-catalyzed diarylamine formation from cyclohexanones and anilines.

An efficient strategy for carbazole synthesis from arylureasa nd cyclohexanones under transition metal-free conditions has been developed. The combined use of potassium iodide and iodine could significantly improve the reactione fficiency to provide 2,6-disubstituted9 -arylcarbazoles in moderate to good yields.I nt his kind of transformation,t he whole carbazole moiety (except the nitrogen atom) comes from two equivalents of cyclohexanones.

An efficient strategy for carbazoles and 1,2,4-triarylpyrroles synthesis from anilines and cyclohexanones or acetophenones under transition-metal-free conditions is developed. A variety of disubstituted 9-arylcarbazoles were synthesized in moderate to good yields promoted by KI/I using anilines as the nitrogen and aryl source. Meanwhile, a variety of 1,2,4-triarylpyrroles were also selectively synthesized from anilines and acetophenones in the presence of KI alone.