The reaction of 4-nitro-1,3-diarylbutan-1-ones and ammonium acetate in the presence of morpholine and sulfur provides the corresponding 2,4-diarylpyrroles in excellent yields.
M. Adib, N. Ayashi, F. Heidari, P. Mirzaei, Synlett, 2016, 27, 1738-1742.
The combination of sulfur and DABCO efficiently promotes a reductive coupling/annulation of o-nitrophenols or o-nitroanilines with benzaldehydes. This method represents a simple, straightforward, and green approach to the construction of benzoxazoles and benzimidazoles.
M.-H. D. Dang, L. H. T. Nguyen, P. H. Tran, Synthesis, 2020, 52, 1687-1694.
The condensation of 2-nitrobenzyl alcohols with arylacetic acids provides substituted quinazolines under mild conditions in the presence of urea as a nitrogen source, elemental sulfur as a promoter, DABCO as a base, and DMSO as a solvent. The reaction tolerates functionalities such as chloro, fluoro, trifluoromethyl, thienyl, and indolyl groups.
K. X. Nguyen, D. K. Nguyen, P. H. Pham, H. V. Le, T. T. Nguyen, N. T. S. Phan, Synlett, 2020, 31, 1112-1116.