Manganese‐Catalyzed Hydroborations with Broad Scope

Abstract

Reductive transformations of easily available oxidized matter are at the heart of synthetic manipulation and chemical valorization. The applications of catalytic hydrofunctionalization benefit from the use of liquid reducing agents and operationally facile setups. Metal‐catalyzed hydroborations provide a highly prolific platform for reductive valorizations of stable C=X electrophiles. Here, we report an especially facile, broad‐scope reduction of various functions including carbonyls, carboxylates, pyridines, carbodiimides, and carbonates under very mild conditions with the inexpensive pre‐catalyst Mn(hmds)2. The reaction could be successfully applied to depolymerizations.

Accessing Reactive Metal Hydrides through Designed Heterometallic Bridges

“…8 Hexanuclear Mn-H complexes have also been demonstrated to be competent hydrofunctionalization catalysts with wide scope (Scheme 1a). 9 Towards development of a more thorough understanding of the heightened reactivity, facile and modular access to multimetallic hydrides is needed. Unfortunately, the synthetic methods are often non-selective in the formation sought-after multimetallic complexes.…”

First‐Row Transition Metal‐Catalyzed Single Hydroelementation of N‐Heteroarenes

“…Given such backgrounds, von Wangelin developed a simple catalytic procedure using Mn[N(SiMe 3 ) 2 ] 2 ( 2 ) [N(SiMe 3 ) 2 =hmds] as a precatalyst for hydroboration of various unsaturated functions including pyridines and quinolines (Scheme 5). [30] A range of pyridines and (iso)quinolines underwent 1,2‐selective hydroboration with HBpin (pinacolborane, 2 equiv) at 50 °C in the presence of catalytic 2 to give the corresponding 1,2‐DHP and ‐DHQ in good to excellent yields in 72 h. This Mn catalysis was tolerant of halide, CF 3 , and alkoxy groups, and 3‐ and/or 4‐substituted pyridines and quinolines were smoothly reduced to mainly the 1,2‐dihydro products. This work represents the first example of Mn‐catalyzed hydroboration of N‐heteroarenes.…”

“…Following the von Wangelin's first example, [30] very recently the Liu group communicated the second example of the Mn‐catalyzed hydroboration of N‐heteroarenes [31] . In the Liu's catalytic system, a broad range of quinolines underwent regioselective 1,4‐hydroboration under a mode of metal‐ligand cooperation (MLC), as several catalytic procedures via MLC were previously reported for hydroboration of unsaturated functions (Scheme 7).…”

A N‐Heterocyclic Carbene‐Supported Zinc Catalyst for the 1,2‐Regioselective Hydroboration of N‐Heteroarenes

“…Catalysts known for the regioselective 1,2‐hydroboration of pyridine and other N‐heteroarenes include Rh (1 mol %, 50 °C), [14] La (1 mol %, 25–35 °C), [15] Th (2 mol %, 70 °C), [16] Fe (1 mol %, 50 °C), [17] Mn (5 mol %, 50 °C), [18] Ni (5 mol %, 30 °C), [19] Mg (2 mol %, 25 °C), [20] and Zn (5–10 mol %, 70 °C) [21] . However, none of them uses an NHC‐support like the present case.…”