In the past decades, the development of transition metal catalyzed C-H functionalization boosted the scope of C-C and C-X (X = C, O, N, P, S) bond formation reactions. This methodology has had a great impact on the areas of synthetic chemistry, medicinal chemistry and material sciences. These reactions require the in-situ activation of the C-H bonds that results in a oxidative/dehydrogenative coupling leading to the formation of the desired product. Various transition-metal complexes especially palladium, platinum and ruthenium have gained tremendous success in carrying out various C-H activation reactions. These metals have broad synthetic scope and the possibility to control the selectivity of the transformations, which is an attractive feature in catalysis. Moreover, these metal complexes are stable, highly selective, have high turnover numbers and low catalyst loadings. However, these precious metals, although carry out rapid, time-effective and selective reactions, are expensive, more toxic, limited in supply and hard to remove from the reaction product. Hence non-precious metals (first row transition metals) have gained much popularity over these rare metals in recent years due to their low toxicity, and unique reactions mechanism. In our current project, we are exploring the effect of non-precious nickel metal catalysts for the synthesis of Guerbet Alcohols, the reaction that involves the conversion of primary alcohols into the corresponding b-alkylated dimeric alcohol with the loss of water. The simple, inexpensive and readily available substrates make this an important and atom efficient reaction. Recently recyclable impregnated iridium oxide on magnetite as a heterogeneous catalyst was used for the synthesis of Gurebet alcohols. Ruthenium catalysts was also used recently for the synthesis of α,β-unsaturated aldehydes. A wide substrate scope of the reaction was demonstrated to prepare a wide variety of Guerbet alcohol derivatives.24f However, the methods reported till date only used the precious metals for the synthesis of Guerbet alcohols. In this project, we are exploring the use of nickel and nickel-complexes for the cross-coupling reaction of primary alcohols for the direct synthesis of Guerbet Alcohols.

Non-precious metal catalyzed direct synthesis of Guerbet alcohol

2019 Fall National Meeting

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