A simple protocol of manganese catalyzed selective αalkenylation of ketones using primary alcohols is reported. The reactions proceeded well with a low loading of catalyst (0.3 mol %). The overall transformation operates through O−H bond activation of primary alcohols via dearomatization−aromatization metal ligand cooperation in the catalyst to provide the corresponding aldehydes, which further undergo condensation with methylene ketones to deliver α,β-unsaturated ketones. This selective α-alkenylation proceeds with the release of water and liberation of molecular hydrogen.

Catalytic cross-coupling of ketones and secondary alcohols with primary alcohols is reported. An abundant manganese-based pincer catalyst catalyzes the reactions. Low loading of catalyst (2 mol %) and catalytic use of a mild base (5–10 mol %) are sufficient for efficient cross-coupling. Various aryl and heteroaryl ketones are catalytically cross-coupled with primary alcohols to provide the selective α-alkylated products. Challenging α-ethylation of ketones is also attained using ethanol as an alkylating reagent. Further, direct use of secondary alcohols in the reaction results in in situ oxidation to provide the ketone intermediates, which undergo selective α-alkylation. The reaction proceeds via the borrowing hydrogen pathway. The catalyst oxidizes the primary alcohols to aldehydes, which undergo subsequent aldol condensation with ketones, promoted by catalytic amount of Cs 2 CO 3 , to provide the α,β-unsaturated ketone intermediates. The hydrogen liberated from oxidation of alcohols is used for hydrogenation of α,β-unsaturated ketone intermediates. Notably either water or water and dihydrogen are the only byproducts in these environmentally benign catalytic processes. Mechanistic studies allowed inferring all of the intermediates involved. Dearomatization–aromatization metal–ligand cooperation in the catalyst facilitates the facile O–H bond activation of both primary and secondary alcohols, and the resultant manganese alkoxide complexes produce corresponding carbonyl compounds, perhaps via β-hydride elimination. The manganese(I) hydride intermediate plays dual role as it hydrogenates α,β-unsaturated ketones and liberates molecular hydrogen to regenerate the catalytically active dearomatized intermediate. Metal–ligand cooperation allows all of the manganese intermediates to exist in same oxidation state (+1) and plays an important role in these catalytic cross-coupling reactions.

Herein, unprecedented manganese-catalyzed direct α-alkenylation of amides using alcohols is reported. Aryl amides are reacted with diverse primary alcohols, which provided the α,β-unsaturated amides in moderate to good yields with excellent selectivity. Mechanistic studies indicate that Mn­(I) catalyst oxidizes the alcohols to their corresponding aldehydes and also plays an important role in efficient CC bond formation through aldol condensation. This selective olefination is facilitated by metal–ligand cooperation by the aromatization–dearomatization process operating in the catalytic system. Biorenewable alcohols are used as alkenylation reagents for the challenging α-alkenylation of amides with the highly abundant base metal manganese as a catalyst, which results in water and dihydrogen as the only byproduct, making this catalytic transformation attractive, sustainable, and environmentally benign.

Herein, a catalytic cross-coupling of methyldiphenylphosphine oxide with arylmethyl alcohols leading to the alkenylphosphine oxides is reported. A manganese pincer catalyst catalyzes the reactions, which provides exclusive formation of trans-alkenylphosphine oxides. Mechanistic studies indicate that reactions proceed via aldehyde intermediacy and the catalyst promotes the CC bond formation. Reactions are facilitated by dearomatization, and aromatization metal-ligand cooperation operates in catalyst. Use of abundant base metal catalyst and formation of water and H 2 as the only byproducts make this catalytic protocol sustainable and environmentally benign.