Reduction of Nitroarenes to Anilines with a Benzothiazoline: Application to Enantioselective Synthesis of 2-Arylquinoline Derivatives

Abstract

The metal-free reduction of nitroarenes to aniline derivatives was accomplished in a short time by using a benzothiazoline as the hydrogen donor in combination with a Brønsted acid. An enantioselective synthesis of 2-arylquinolines was achieved by using 1-aryl-3-(2-nitrophenyl)propan-1-ones as starting materials and a combination of a benzothiazoline and a chiral phosphoric acid.

Chiral Phosphoric Acids as Versatile Tools for Organocatalytic Asymmetric Transfer Hydrogenations

“…Recently, the Akiyama group established a highly enantioselective methodology for the synthesis of 2-aryltetrahydroquinolines (99 a-c). [91] After optimizing the reduction of various achiral nitroarenes, a three-step reaction cascade was developed: the initial reduction of the nitroarene (I) was followed by intra-…”

Reduction of Nitroarenes via Catalytic Transfer Hydrogenation Using Formic Acid as Hydrogen Source: A Comprehensive Review

“…[8][9] Alternatively to Bechamp's reduction, the nitro group into nitroarene can be reduced to corresponding aromatic amines through two chemical processes: (i) the catalytic direct hydrogenation using molecular hydrogen (H 2 ) or (ii) the hydrogenation transfer using a hydrogen source. The first is catalyzed by specific transition metals such as iron, nickel, palladium or platinum in presence of molecular hydrogen under special pressure conditions, [8b,10-16] whereas the second strategy employs hydrogen sources for the transfer hydrogenation process such as hydrides (e. g. NaBH 4 or hydrosilanes, [17][18][19][20][21][22][23][24][25] hydrazine hydrate, [17,[26][27][28][29][30] organic reagents (e. g. alcohol, glycerol or formic acid) [17,[31][32][33] and more recently, boron reagents. [34][35] Other methods based on reduced sulfur reagents like elemental sulfur, [36][37] dithionite [38] or sulfides [39] are useful for the reduction of nitro group, being particularly convenient for the selective reduction of polynitroarenes.…”

“…As an alternative to the typical catalytic hydrogenation using H 2 for the reduction of nitro group highlights the heterogeneous catalytic transfer hydrogenation (CTH), which emerged as a more controlled strategy because the hydrogen is generated in situ using a hydrogen donor and represents a valuable strategy by their minor procedure risk, simplicity, cost-effective and sustainability. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] The design of this strategy is focused on the selection of the metallic catalyst and the hydrogen sources. The nature of catalyst is very variable and a large number of examples can be found including catalyst based on coinage (Au, Ag, Cu), noble (mostly Pd, Pt and Ru) and non-noble (Ni, Co, Fe) metals.…”

“…NaBH 4 or hydrosilanes, [17–25] hydrazine hydrate, [17,26–30] organic reagents ( e. g . alcohol, glycerol or formic acid) [17,31–33] and more recently, boron reagents [34–35] . Other methods based on reduced sulfur reagents like elemental sulfur, [36–37] dithionite [38] or sulfides [39] are useful for the reduction of nitro group, being particularly convenient for the selective reduction of polynitroarenes.…”

“…morpholine, phosphorous acid); [44] however, the control of the selectivity is even persistent in the catalytic hydrogenation. As an alternative to the typical catalytic hydrogenation using H 2 for the reduction of nitro group highlights the heterogeneous catalytic transfer hydrogenation (CTH), which emerged as a more controlled strategy because the hydrogen is generated in situ using a hydrogen donor and represents a valuable strategy by their minor procedure risk, simplicity, cost‐effective and sustainability [17–35] . The design of this strategy is focused on the selection of the metallic catalyst and the hydrogen sources.…”