Atom Economy, description

Cyanohydrins are usually prepared from carbonyl compounds and a cyanide source. Initially performed with volatile and very toxic hydrogen cyanide, the reaction is now carried out with safer cyanide agents, such as acetone cyanohydrin, acyl cyanides, cyanoformates or the most used trimethylsilyl cyanide. In terms of atom economy, this reaction is 100% atom efficient and is widely used despite the toxicity of the reagents. The asymmetric reaction can now be efficiently catalysed by a variety of chiral Lewis acids, and a recent review presents in detail the work realised in this field, with a large description of titanium-based catal)dic systems. 

These kinds of reactions necessarily have low minimum atom economies particularly if the sacrificial reagents are of high molecular weight compared to the substrate of interest. A brief description of the role of the sacrificial reagents is also given. 

The gas-phase selective oxidative transformation of light alkanes is an important challenge as it could reduce the number of process steps, decreasing both the energy required and CO2 emissions, and improve the atom economy. In this chapter a summary of both the oxidative dehydrogenation and the O-insertion for C2-C4 alkanes is presented. In addition, an alternative method for abetter selective oxidative transformation of methane and a description of the best catalytic systems are discussed. 

Dipolar cycloaddition reactions (DCRs) are unique reactions when considering their versatility, their atom economy and the highly functionalized heterocyclic products they provide. The significant contributions by Rolf Huisgen has led to the description of a... 

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