Substrate reagent-directing group

A way to overcome such an intrinsic limitation may provide a specifically introduced reagent-directing group into an organic substrate (see Scheme 1). 

Chelate-assisted C-H bond trifluoromethylations are rare, and so far, only two reagents have been used successfully in these reactions. The first reagent 19 is an electrophilic source of CF, which reacts under Pd catalysis with substrates bearing directing groups (Scheme 23.27) [92, 93]. The reaction also requires the presence of Cu(OAc)j and trifluoroacetic acid as promoters both amide-based and heterocyclic directing groups can be employed. 

In order to avoid these limitations, efforts have been made to find ways of coupling substrate turnover directly to a selection process. Two groups have devised a method that involves the attachment of a substrate to a phage-enzyme in a way that allows its intraphage interaction with the enzyme. Phage-displaying active enzymes are able to convert the substrate into product. They can be captured from mixtures with product specific reagents or antibodies. 

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