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2-(N-alkylamino)pyrimidines are important heterocycles widely found in various pharmaceutically important drugs. Here, we have disclosed a new cooperative ruthenium complex catalyzed tandem multicomponent synthesis of 2-(N-alkylamino)pyrimidines directly from guanidine salt and alcohols. The reactions proceeded through the dehydrogenation of alcohols, followed by C C coupling and sequential C N coupling with guanidine and primary alcohol, with the elimination of three equivalents of hydrogen gas. In this work, application of both the acceptorless dehydrogenative coupling (ADC) and borrowing hydrogen (BH) strategies were accomplished in a single reaction. This catalytic method tolerated a wide range of substrates. The viability of the current method was demonstrated by preparative scale synthesis of a few products. A plausible catalytic cycle was proposed based on various control experiments, mechanistic studies and DFT calculations. Remarkably, 42 new 2-(N-alkylamino)pyrimidines were synthesized following this catalytic protocol.

The synthesis of heterocycles is an emerging area of chemical research considering their high importance in pharmaceuticals, material chemistry, and natural product synthesis. The development of greener methodologies by employing easily available renewable starting materials has been a long thirst for synthetic chemists. Alcohol is an economical and abundantly available greener substrate produced from diverse sustainable resources. The transition metal-catalyzed acceptorless dehydrogenative coupling (ADC) strategy offers the environmentally benign synthesis of numerous N-heterocycles using alcohols, since only water and hydrogen are produced as the eco-friendly by-products. In this review, we have summarized various aspects of homogeneous and heterogeneously catalyzed recent advancements in the synthesis of heterocycles following the ADC approach.

Functionalization of alcohol is a promising field in synthesis for the possible conservation of fossil-based-feedstocks, since alcohols can be easily obtained from readily available biomass. Despite the widespread advancement, functionalization of alcohols was predominantly studied using precious metal-based catalysts. The utilization of abundant 3d-metals in catalysis is a cost-effective alternative to their higher congeners. In this context, cobalt is a promising entrant owing to its exceptional catalytic activity and selectivity, unique redox behavior, and diverse reaction mechanism than other transition metals. This review features the advancement in cobalt-catalyzed, both homogeneous and heterogeneous, dehydrogenation of alcohols, numerous C C and C N bond formation reactions, synthesis of heterocycles, and other valuable products formation following the borrowing hydrogen (BH) and acceptorless dehydrogenative coupling (ADC) strategy.