Copper(II) Complexes of Arylhydrazone of 1H-Indene-1,3(2H)-dione as Catalysts for the Oxidation of Cyclohexane in Ionic Liquids

Abstract

The copper(II) complexes [CuL(H 2 O) 2 ]·H 2 O (1) and [CuL(dea)] (2) [L = 2-(2-(1,3dioxo-1H-inden-2(3H)-ylidene)hydrazinyl)benzenesulfonate, dea = diethanolamine] were applied as catalysts in the peroxidative (with tert-butyl-hydroperoxide or hydrogen peroxide) conversion of cyclohexane to cyclohexanol and cyclohexanone, either in acetonitrile or in any of the ionic liquids [bmim][NTf 2 ] and [hmim][NTf 2 ] [bmim = 1-butyl-3-methylimidazolium, hmim = 1-hexyl-3-methylimidazolium, NTf 2 = bis(trifluoromethanesulfonyl) imide]. Tert-butylhydroperoxide led to better product yields, as compared to H 2 O 2 , with a selectivity directed towards cyclohexanone. The ILs showed a better performance than the conventional solvent for the copper complex 1. No catalytic activity was observed for 2 in the presence of an IL.Despite the potential applications of arylhydrazone and their metal complexes, mainly in the oxidation of alkanes and alcohols [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53], the use of such compounds in catalysis is still an understudied area. In pursuit of our interest in the transition metal-catalysed peroxidative [by tert-butyl hydroperoxide (TBHP) or H 2 O 2 ] oxidation of hydrocarbons in ILs [36-39], we have tested a pair of already known [51] copper(II) complexes, viz. [CuL(H 2 O) 2 ]·H 2 O (1) and [CuL(dea)] (2), as catalysts for cyclohexane conversion into cyclohexanol and cyclohexanone (Scheme 1), in acetonitrile or in any of the ionic liquids [bmim][NTf 2 ] or [hmim][NTf 2 ] as solvents and under low-power (10 W) microwave irradiation. The favorable effect of microwaves (MWs) in comparison with conventional heating has been recognized in alkane oxidation [54].

Mild Liquid Phase Oxidation of Benzyl Alcohol in the Presence of Microporous Framework Copper Silicates

“…5.3 Å molecular size, capable of entering the 12‐MR channels) was strongly inhibited by the radical scavenger; 1 and 2 led to 5 and 15 % conversion at 6 h, respectively, compared to 30 and 48 % conversion without radical scavenger, respectively (Table entries 1, 6). Hence, the copper silicates promoted t BuOOH activation, which may give tert ‐butylperoxyl, tert ‐butoxyl and hydroxyl radicals (Equations 1, 2), in line with different transitions metal‐catalysed peroxidative oxidation reactions . The radicals may react with BzOH (RCH 2 ‐OH in Equations 3, 4) giving benzyl alcohol radicals (RCH · –OH in Equations 5–7),, , and subsequently BzAld (RCHO) , .…”

Cyanosilylation of Aldehydes Catalyzed by Ag(I)- and Cu(II)-Arylhydrazone Coordination Polymers in Conventional and in Ionic Liquid Media

“…To date, a few ILs have been reported in the cyanosilylation of aldehydes [52,53]. Thus, another aim of this work is to use a cooperative action of ILs and coordination polymers in cyanosilylation reaction, a type of approach that we have successfully applied in the oxidation of alkanes [54,55] and oxidation of alcohols [56].…”