Iron‐Catalyzed α‐Alkylation of Ketones with Alcohols

Abstract

A general and benign iron-catalyzed α-alkylation reaction of ketones with primary alcohols has been developed. The key to success of the reaction is the use of a Knölker-type complex as catalyst (2 mol %) in the presence of Cs2 CO3 as base (10 mol %) under hydrogen-borrowing conditions. Using 2-aminobenzyl alcohol as alkylation reagent allows for the "green" synthesis of quinoline derivatives.

Iron‐Catalyzed Allylic Amination Directly from Allylic Alcohols

“…Based on the experimental observations and relevant reports on the use of Knölker's complex for borrowing hydrogen methodology (redox process),, we proposed a possible mechanism for the Fe‐catalyzed allylic amination directly from alcohol (Scheme ). First, the de‐coordination of CO in the presence of Me 3 NO gives 16e − unsaturated complex B , which upon coordination with an alcohol leads to intermediate complex C —in which the alcohol was activated through the hydrogen bonding between the alcoholic hydrogen and cyclopentadienone.…”

Manganese‐Catalyzed Hydrogen‐Autotransfer C−C Bond Formation: α‐Alkylation of Ketones with Primary Alcohols

“…[3] Hydrogen autotransfer, which is commonly performed with noble metals,s uch as ruthenium and iridium, constitutes ag reener alternative. [5] Apart from iron, manganese is attracting increasing interest in synthesis,s ince it is cheap and toxicologically benign in comparison to most other transition metals.Itisalso an abundant element on Earthsc rust and is capable of existing in several oxidation states.Awide variety of derivatives are readily available,a nd the number of manganese-catalyzed transformations has increased considerably during the last few years. [5] Apart from iron, manganese is attracting increasing interest in synthesis,s ince it is cheap and toxicologically benign in comparison to most other transition metals.Itisalso an abundant element on Earthsc rust and is capable of existing in several oxidation states.Awide variety of derivatives are readily available,a nd the number of manganese-catalyzed transformations has increased considerably during the last few years.…”

“…[5] Apart from iron, manganese is attracting increasing interest in synthesis,s ince it is cheap and toxicologically benign in comparison to most other transition metals.Itisalso an abundant element on Earthsc rust and is capable of existing in several oxidation states.Awide variety of derivatives are readily available,a nd the number of manganese-catalyzed transformations has increased considerably during the last few years. [8] On the basis of our recent study on the iron-catalyzed aalkylation of ketones with alcohols, [5] we became interested in the catalytic application of manganese(I) pincer complexes for such transformations (Scheme 1). [8] On the basis of our recent study on the iron-catalyzed aalkylation of ketones with alcohols, [5] we became interested in the catalytic application of manganese(I) pincer complexes for such transformations (Scheme 1).…”

“…[6] Despite all this progress,the use of manganese in dehydrogenative coupling processes is scarce, [7] and to the best of our knowledge no catalytic hydrogenautotransfer CÀCb ond-forming processes in the presence of defined molecular manganese complexes have been described previously. We therefore prepared precatalysts 1-3 by the treatment of the corresponding tridentate ligands with [Mn(CO) 5 Br] (see the Supporting Information for ageneral procedure). We therefore prepared precatalysts 1-3 by the treatment of the corresponding tridentate ligands with [Mn(CO) 5 Br] (see the Supporting Information for ageneral procedure).…”

“…To our delight, the use of 3mol %o fp incer complexes 1-3 for the reaction of 4a (1 mmol) with 5a (1.2 mmol) in the presence of Cs 2 CO 3 (10 mol %) in 1,4dioxane at 150 8 8Ca llowed the alkylated ketone 6a to be obtained selectively in good yields (77-90 %; Table 1, entries 1-3). Thed iisopropylphosphine derivative 3 was the most effective precatalyst, whereas [Mn(CO) 5 Br],t he precursor in the preparation of the pincer complexes,o nly Scheme 1. Manganese-catalyzed a-alkylation of ketones with alcohols.…”