3d-Metal Catalyzed C–C Bond Formation Through α-Alkylation of Ester, Amide, and Nitriles with Alcohol via Dehydrogenative Coupling

The borrowing hydrogenation (BH) and acceptorless dehydrogenative coupling (ADC) methods emerged as sustainable tools for forging carbon–carbon bonds at remarkably benign conditions. These protocols utilize alcohol as an alkylating reagent, producing water (and hydrogen gas) as by-products. This makes them advantageous over the traditional C-alkylation procedure, which requires an organohalide reagent and harsh conditions. Considering the importance of alkylated carboxylate derivatives in pharmaceutical research, their cost-effective preparation is highly demanding. Moreover, due to the less acidity of the α-hydrogen atoms of unactivated esters, amides, and nitriles, their C-alkylation remained challenging. Toward this aim, hydrogen transfer-mediated α-alkylation of these carboxylate derivatives is an attractive choice. Significant progress has been made using catalysts based on precious transition metals, including rhodium, iridium, osmium, and ruthenium. Due to the toxicity, high cost, and limited availability of these noble metals, replacing them with 3d metals would make these processes more sustainable and economically attractive. In this chapter, we discuss the progress made in the hydrogen transfer-mediated C–C bond formation reactions through α-alkylation/olefination of esters, amides, and nitriles using alcohols as carbon sources with the aid of well-defined 3d metal complexes as the catalyst.