Rapid reduction of heteroaromatic nitro groups using catalytic transfer hydrogenation with microwave heating

Selective Reduction of Halogenated Nitroarenes with Hydrazine Hydrate in the Presence of Pd/C

“…Numerous selective reductions on chlorinated nitroarenes have been reported with the problem of enhanced reductive dehalogenation caused by an in situ produced amino group. 6 Therefore, a mild, universal strategy for the selective reduction of halogenated nitroarenes is highly desired to replace harsher (for example Zn/H + ) or non-selective conditions. Herein, we report a simple, efficient, and highly selective reduction of halogenated nitroarenes.…”

Toward a Continuous‐Flow Synthesis of Boscalid®

“…[26] However, in the case of 4'-chloro-2-nitrobiphenyl (3), the use 1 mol% of a standard 10% (w/w) Pd/C catalyst led to a significant over reduction, producing~25% (GC-MS) of the undesired 2-aminobiphenyl by-product (7, see Table 2) in addition to the target Boscalid intermediate 2-amino-4'-chlorobiphenyl (4). Gratifyingly, using 1 mol% of a 5% (w/w) Pt/C catalyst [27] and 5 equivalents of cyclohexene at 150 8C in EtOH, clean and complete reduction of the nitro group was obtained providing 2-amino-4'-chlorobiphenyl (4) within 30 min in 81% isolated yield after solvent removal and subsequent flash chromatography. Under these conditions only trace amounts of the dehalogenated 2-aminobiphenyl product (7) were observed (GC-MS, < 1%).…”

Pd/C Catalysis under Microwave Dielectric Heating

“…Alternatively, the fully deprotected H-Phe-OH 103 was obtained using EtOAc. The same authors reported later a general reduction of arylnitro derivatives with Pd/C and 1,4-cyclohexadiene at 120 • C for 5 min (Scheme 30) [83]. Moreover, 1-methyl-1-cyclohexene has been used as a source of hydrogen with the obvious advantage of producing the safer toluene as the oxidized product.…”

“…Alternatively, the fully deprotected H-Phe-OH 103 was obtained using EtOAc. The same authors reported later a general reduction of arylnitro derivatives with Pd/C and 1,4-cyclohexadiene at 120 °C for 5 min (Scheme 30) [83]. …”