Tetrabutylammonium Bromide-Catalyzed Transfer Hydrogenation of Quinoxaline with HBpin as a Hydrogen Source

Abstract

A metal-free environmentally benign, simple, and efficient transfer hydrogenation process of quinoxaline has been developed using the HBpin reagent as a hydrogen source. This reaction is compatible with a variety of quinoxalines offering the desired tetrahydroquinoxalines in moderate-to-excellent yields with Bu4NBr as a noncorrosive and low-cost catalyst.

Metal-free cascade reactions for one-pot tetrahydroquinoxaline construction through nitroarene reduction and imine hydrogenation with water

“…On the basis of these results, we wonder if 1,2-diaminobenzene can be simply obtained, which has been used in the synthesis of dihydroquinoxalinones and tetrahydroquinoxalines, leading to diverse applications in pharmaceuticals, agrochemicals, and materials science. 2,3 Compared to the hydrogenation of quinoxalinones and quinoxalines, [24][25][26][27] this method starts from raw materials and avoids the preparation of substrates, reserving elemental economy. [28][29][30] When we increase the amount of B 2 cat 2 , 1,2-dinitrobenzene can be reduced to 1,2-diaminobenzene by controlling the reaction conditions (Scheme S1, ESI †), indirectly indicating that 2-nitroaniline can also be reduced to 1,2-diaminobenzene.…”

H2O/D2O as the only H/D source for photocatalytic phosphine-mediated radical transfer hydrogenation/deuteration of α-aryl imino esters

“…However, their overall benefits are not optimal due to the substantial production of chemical by-products. 5…”