The review summarizes the recent progress on manganese-catalyzed (de)hydrogenation and hydroelementation reactions. It provides a complete and critical analysis of ligand design, reaction pathways, and synthetic applications.

Acceptorless dehydrogenative coupling (ADC) has emerged as a powerful tool in the chemists’ arsenal for the construction of various carbon‐carbon and carbon‐heteroatom bonds. These protocols are highly atom economical and environmentally benign as they do not require pre‐functionalized starting material and produce only dihydrogen (and water) as the by‐product. This technique, coupled with Earths’ abundant and less toxic manganese catalysis, can prove to be a vital strategy for the generation of molecular complexity from simple starting materials. Manganese catalyzed DHC has been of growing interest, and various low‐ and high‐valent manganese catalysts have been developed. These catalysts were demonstrated to show excellent catalytic activity for the formation of carbon‐carbon, carbon‐heteroatom bonds, and cascade reactions. In this mini‐review, we would like to highlight the recent progress that has been made in manganese catalyzed ADC reactions.

Herein, we present the first catalytic direct olefination of methyl-substituted heteroarenes with primary alcohols through an acceptorless dehydrogenative coupling. The reaction is catalyzed by a complex of the earth-abundant transition metal manganese that is stabilized by a bench-stable NNN pincer ligand derived from 2-hydrazinylpyridine. The reaction is environmentally benign, producing only hydrogen and water as byproducts. A large number of E-disubstituted olefins were selectively obtained with high efficiency.

Diverse β-functionalised carbonyl compounds were synthesized via a manganese(i) complex-catalysed α-alkylation of ketones with secondary alcohols.

The development of first-row-transition-metal catalysts that can match with the reactivities of the noble metals is considered to be challenging yet very much a desirable goal in homogeneous catalysis. It has become even more fascinating to develop processes where these metals show a unique reactivity and selectivity than their higher congeners. Herein, we report on the catalytic activity of a pincer complex of the abundant earth metal manganese for an unprecedented acceptorless dehydrogenative coupling of alkyl sulfones with alcohols. Thus, highly functionalized vinyl sulfones were obtained in moderate to good yields. Both benzylic and aliphatic alcohols could be utilized, and several functional groups including bromides and iodides are tolerated under the reaction conditions. The reaction is environmentally benign, producing dihydrogen and water as byproducts. Preliminary mechanistic experiments involving kinetic, deuterium-labeling, and NMR experiments were performed.

Conversion of readily available feedstocks to valuable platform chemicals via an eco-friendly catalytic pathway has always been one of the key focuses of synthetic chemists. In this context, herein, we report selective transformation of readily available feedstock, vicinal glycols, to value-added α-hydroxycarboxylic acid molecules that are prevalent in bioactive molecules and biodegradable polymers. A bench stable Earth-abundant metal complex, {[HN(C 2 H 4 PPh 2 ) 2 ]Mn(CO) 2 Br}, Mn-I catalyzed the reformation reaction at low temperature in high selectivity with a turnover number reaching 2400, surpassing previously used homogeneous catalysts for such a reaction. Hydrogen gas is evolved as a byproduct without needing an acceptor. The developed protocol is applicable for both aromatic and aliphatic vicinal glycols, delivering the α-substituted hydroxycarboxylic acids in high yields and selectivities. Detailed mechanistic studies elucidated the involvements of different manganese(I)-species during this acceptorless dehydrogenation catalysis.

Herein, a base-metal nickel-catalyzed direct olefination of alcohols with sulfones is reported. The reaction operates under low catalyst loading and does not require an external redox reagent. A wide range of trans -stilbenes and styrenes were synthesized in good yields and selectivities. Biologically active stilbene DMU-212 could also be synthesized in a single step under these conditions. Mechanistic studies involving kinetic isotope effect, deuterium labeling experiments, and catalytic and stoichiometric reactions with possible catalytic intermediates were performed to elucidate a plausible mechanism.

Herein, we present the first catalytic direct olefination of methyl-substituted heteroarenes with primary alcohols through an acceptorless dehydrogenative coupling.T he reaction is catalyzedbyacomplex of the earth-abundant transition metal manganese that is stabilized by ab ench-stable NNN pincer ligand derived from 2-hydrazinylpyridine.The reaction is environmentally benign, producing only hydrogen and water as byproducts.Alarge number of E-disubstituted olefins were selectively obtained with high efficiency.