Raney Ni–Al alloy-mediated reduction of alkylated phenols in water

Abstract

Raney Ni-Al alloy in a dilute aqueous alkaline solution has been shown to be a very powerful reducing agent in the hydrogenation of phenol and alkylated phenols to the corresponding cyclohexanol derivatives.

Reductive approach in the degradation of phenols with zero‐valent iron in aqueous media

“…According to this possible reduction route from the phenol to the corresponding cyclohexanol, the cyclohexanone is more an intermediate than a reaction product. When comparing to the previously reported methods [28,29], which both presented a 100% conversion of phenols (same as the present one), it can be noted that even if the aqueous reduction with Ni-Raney needs only a 1%KOH solution, the reaction time is extremely long (over 10 h for the shortest tests) and the temperature is 90 C [28]. The second method is much shorter (~15 to 40 min) for a complete conversion, but the method is costly and ultrasonication activation is difficult to apply to higher quantities (especially when considering wastewaters) [29].…”

“…There are only two previous reports for the transformation of phenols in aqueous media in cyclohexanols or cyclohexanones. Thus, the formation of cyclohexanols in aqueous media was achieved using a Ni‐Raney alloy, in the presence of a strong base , while cyclohexanones were obtained in water using sodium formate and Pd/C as catalyst, in an ultrasonic activation .…”

Continuous-Flow Biocatalytic Process for the Synthesis of the Best Stereoisomers of the Commercial Fragrances Leather Cyclohexanol (4-Isopropylcyclohexanol) and Woody Acetate (4-(Tert-Butyl)Cyclohexyl Acetate)

“…From compound 4 (500 mg, 3.57 mmol), derivative cis-1 was obtained (461 mg, 91%, de = 87%): 1 H NMR (CDCl 3 , 400 MHz) [5]: δ = 3.99 (m, 1H, CHOH), 1.79-1.72 (m, 2H, hydrogens of cyclohexane ring), 1.53-1.41 (m, 7H, hydrogens of cyclohexane ring), 1.09-1.02 (m, 1H, CH(CH 3 ) 2 ), 0.88 (d, 6H, J = 6.8 Hz, C(CH 3 ) 2 ). 13 C NMR (CDCl 3 , 100.6 MHz): δ = 66.6, 43.4, 32.7, 32.0, 23.7, 19.9.…”

“…It is very likely that the same difference does exist for compounds cisand trans-1. Mixtures of cisand trans-4-alkylcyclohexanols 1 and 3 are usually obtained by liquid-phase hydrogenation of 4-alkylphenols over supported metal catalysts in organic solvent [3][4][5]. In these conditions, however, the thermodynamically more stable transisomer is also formed simultaneously, most frequently as the main product.…”

Raney Ni-Al alloy mediated hydrodehalogenation and aromatic ring hydrogenation of halogenated phenols in aqueous medium

“…In the continuation of our work on the reduction of halogenated aromatic compounds, 17,18 we turned our attention to developing a convenient, eco-friendly and practical method for the hydrodehalogenation and hydrogenation of chloroand bromophenols. It was found that Raney Ni-Al alloy in a dilute aqueous alkaline solution effectively reduces phenols to cyclohexanol.…”