Directing Group Strategies In Catalytic Sp(2) C-H Cyanations: Scope, Mechanism And Limitations

Aryl nitriles are key structural motifs in numerous important dyes, agrochemicals, natural products and drug molecules. They are also well known as versatile intermediates for the rapid synthesis of diverse organic compounds such as amines, amidines, tetrazoles, aldehydes, amides and carboxylic acids. In recent years, transition metal-catalyzed sp(2) C-H bond cyanation has attracted considerable attention and significant progress has been made in this field. As a major advancement in this field, the directing group strategy in transition metal-catalyzed sp(2) C-H bond cyanation has contributed significantly to the direct conversion of cheap hydrocarbons to synthetically versatile cyano-containing compounds, which features the advantages of high efficiency, no pre-functionalization of the substrate, low pollution etc. In this minireview with sections classified by the type of different metal-mediated catalytic systems, we mainly focus on catalytic methodologies of transition metal-catalyzed sp(2) C-H bond cyanation assisted by a directing group, with emphasis on reaction scopes, limitations and mechanisms. In addition, the future development prospects of this specific field are also introduced.