Iron‐Catalyzed Chemoselective Reduction of α,β‐Unsaturated Ketones

Abstract

An iron-catalyzed chemo- and diastereoselective reduction of α,β-unsaturated ketones into the corresponding saturated ketones in mild reaction conditions is reported herein. DFT calculations and experimental work underline that transfer hydride reduction is a more facile process than hydrogenation, unveiling the fundamental role of the base.

Recent Catalytic Applications of (Cyclopentadienone)iron Complexes

“…The electron‐rich Fe complexes developed by Poater, Renaud and co‐workers (A), and their use in CH‐based reductive amination (B and F), in the CH of NaHCO 3 (C) / CO 2 (D), and in the chemoselective reduction of α,β‐unsaturated ketones (E) . TMG = 1,1,3,3‐tetramethylguanidine.…”

“…Using pre‐catalyst 5fa – a modified version of 1f in which one CO is replaced by PPh 3 – Poater, Renaud and co‐workers also developed an effective and general protocol for the chemoselective 1,4‐reduction of α,β‐unsaturated ketones by CTH with i PrOH (Scheme E) . Use of cesium bases was found crucial to achieve the desired reaction, which gave good results also with several natural products.…”

Cyclopentadienone Iron Tricarbonyl Complexes-Catalyzed Hydrogen Transfer in Water

“…In 2015, we introduced in catalysis the tricarbonyl iron complex Fe2 bearing a diaminocyclopentadienone ligand [21]. Compared to other cyclopentadienone iron carbonyl complexes, this phosphine-free iron complex has, to the best of our knowledge, the highest catalytic activities to date in reductive amination [21], in chemoselective reduction of α,β-unsaturated ketones [22], in the hydrogenation of carbon dioxide [23], in alkylation of ketones [24][25][26][27], amines [25,28], oxindoles [29], indoles [25,30] and alcohols [31,32]. In our ongoing interest in reduction and alkylation, we thought that a water-soluble analog of Fe2 would be more active than our previous water-soluble cyclopentadienone iron complex Fe3 (Figure 1).…”

Benzylamine as Hydrogen Transfer Agent: Cobalt‐Catalyzed Chemoselective C=C Bond Reduction of β‐Trifluoromethylated α,β‐Unsaturated Ketones via 1,5‐Hydrogen Transfer

“…On the other hand, the chemoselective reduction of a,b-unsaturated carbonyl compounds is one of the most important subjects in synthetic organic chemistry and has attracted much attention from both academia and industry.W ithr egards to the chemoselective C=Cbond reduction of a,b-unsaturated ketones, several efficient and highly selectivem ethodologies have been developed such as catalytic hydrogenation with hydrogen gas [8] and catalytic transfer hydrogenation with alco-hol [9] or other costly hydrogen sources [10][11][12][13] (hydrosilanes, [10] NaBH 4 , [11] Hantzsche ster [12] etc.). However,t he use of benzylamine, being employed as ah ydrogen transfer agent for the chemoselective reduction C=Co fa,b-unsaturated ketones has rarely been reported.…”