2.5.7 Formylation and the Vilsmeier Reagent

Abstract Formylation, allowing the introduction of a formyl group to an organic molecule, is a useful reaction in organic synthesis. The obtained formyl group can be readily reduced to afford alcohols or oxidized to give acids. Moreover, formylation plays a key role in biological and pharmaceutical fields. This chapter covers formylating reagents that are capable of efficiently introducing a formyl group to various organic molecules. Due to the versatility, ease of operation, and tolerance of many functional groups, the Vilsmeier reaction for the formylation of organic compounds is the main focus of this chapter.