Iron-Catalyzed Borrowing Hydrogen β-C(sp³)-Methylation of Alcohols

Abstract

Herein we report the iron-catalyzed β-C(sp 3 )-methylation of primary alcohols using methanol as a C1 building block. This borrowing hydrogen approach employs a well-defined bench-stable (cyclopentadienone)iron(0) carbonyl complex as precatalyst (5 mol %) and enables a diverse selection of substituted 2-arylethanols to undergo β-C(sp 3 )-methylation in good isolated yields (24 examples, 65% average yield).

Recent Catalytic Applications of (Cyclopentadienone)iron Complexes

“…On the other hand, the β‐alkylation of alcohols with methanol and benzylic alcohols was reported (Scheme B) . Almost simultaneously, a paper by Morrill and co‐workers on the β‐methylation of alcohols with methanol using pre‐catalyst 1f was also published (Scheme C) …”

“…Three‐component HB alkylation of methyl ketones (A); β‐alkylation of alcohols reported by Renaud (B) and by Morrill (C) …”

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).…”

A Simple Iron-Catalyst for Alkenylation of Ketones Using Primary Alcohols

“…Interestingly, iron catalysts were extensively used in cross-coupling reactions, [41][42][43][44][45] hydrogenations and transfer hydrogenations, [46][47][48][49], hydrosilylations [50][51][52], as well as in hydroboration processes [53,54]. However, the application of a Knölker-type complex for the alkylation and methylation of ketones and alcohols is noteworthy [55][56][57][58][59]. Nevertheless, Knölker-type iron complexes require a tedious synthesis procedure and are expensive in nature.…”