Reduction of Carbonyl Compounds and Imines Using the CuCl₂·2H₂O-Li-DTBB (Cat.) Combination

Abstract

The reaction of different carbonyl compounds and imines with a mixture of copper(II) chloride dihydrate, an excess of lithium sand, and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol%) in THF at room temperature, led to the formation of the corresponding alcohols and amines, respectively. The process was also applied to the transformation of α,β-unsaturated carbonyl compounds into the corresponding saturated alcohols. The use of the deuterated copper salt CuCl 2 ⋅2D 2 O allowed the preparation of the corresponding deuterated products.

New active-iron based reducing system for carbonyl compounds and imines. Stereoselective reduction of cyclic ketones

“…On the contrary, this side reaction was not observed in the reduction of the ketimine derived from acetophenone and benzylamine, probably due to the shorter reaction time required (Table 2, entry 5). Taking into account the previous reduction studies on carbonyl compounds and imines carried out with other transition-metal salts, we also want to compare herein the reactivity and selectivity of the present reducing system with those of the closely related nickel and copper salts, NiCl 2 $2H 2 O 31 and CuCl 2 $2H 2 O, 7 respectively. Concerning the reactivity, in general, similar results were obtained both in the reduction of carbonyl compounds and imines irrespective of the reducing system used, in all cases with moderate to good yields.…”

“…Concerning the reactivity, in general, similar results were obtained both in the reduction of carbonyl compounds and imines irrespective of the reducing system used, in all cases with moderate to good yields. 7,31 As regards the selectivity, however, the NiCl 2 $2H 2 O-based system showed to be more selective in the reduction of a,b-unsaturated ketones, several examples of which could be transformed into the corresponding saturated ketones or saturated alcohols depending on the amount of salt used. In order to compare the stereoselectivity, 4-tert-butylcyclohexanone, 2-methylcyclohexanone, trans-decalone, and (G)-camphor were used as substrates and subjected to reduction with NiCl 2 $ 2H 2 O, CuCl 2 $2H 2 O, and FeCl 2 $4H 2 O, under the same reaction conditions (Table 3).…”

“…6 More recently, and taking into account the periodic table proximity and the little work published regarding coppermediated reduction reactions, we focused on the copperbased CuCl 2 $2H 2 O-Li-arene (cat.) combination, which was found to be very efficient in the reduction of carbonyl compounds and imines, 7 as well as in the hydrodehalogenation 8a of aryl and alkyl halides. 8b The results obtained thereof together with our ongoing interest in the field above described, encouraged us to explore new metal alternatives to these active-metal based reducing systems, now focusing on iron, as a possible candidate to be used in the reduction or carbonyl compounds and imines.…”

Active-iron-promoted hydrodehalogenation of organic halides

“…The CuCl 2 Á2H 2 O-Li-arene(cat.) system was successfully applied to the reduction of carbonyl compounds and imines [15], as well as to that of sulfonates [16], whereas the FeCl 2 Á4H 2 O-Liarene(cat.) exhibited a remarkable behaviour in the stereoselective reduction of cyclic ketones [17].…”

Reduction of alkyl and vinyl sulfonates using the CuCl2·2H2O–Li–DTBB(cat.) system

“…20 More recently and taking into account the periodic table proximity and the little work published regarding copper-mediated reducing systems, we focused on the copper-based CuCl 2 $2H 2 O-Li-Arene (cat.) combination, which was found to be very efficient in the reduction of carbonyl compounds and imines, 21 as well as in the hydrodehalogenation of aryl and alkyl halides. 22 As part of our research in the field above described, we want to present herein the results obtained on the reduction of alkyl and vinyl sulfonates under very mild reaction conditions, based on the use of active copper, generated from commercially available copper(II) chloride dihydrate, lithium, and a catalytic amount of an arene (DTBB) as electron carrier.…”