Mild, Efficient, and Highly Regioselective Synthesis of 2,6-Diiodobenzaldehyde Derivatives

An efficient and versatile synthesis of 2,6-diiodobenzaldehydes via highly regioselective metal–iodine exchange (MIE) of 5-substituted 1,2,3-triiodobenzenes is reported. The nature of substituents (R) on the phenyl has a large influence on the reactivity of reaction but not on the regioselectivity. The regioselectivity of the MIE can be controlled by the use of ethyl formate as a formylating agent providing only the internal benzaldehyde derivatives in excellent site-selectivity. The best reactivity and the highest isolated yields were furnished with products bearing electron-rich substituents. Several chemical transformations of the target compound as a valuable precursor in synthesis were also demonstrated providing the desired derivatives in good isolated yields. This report discloses a protocol for the synthesis of 2,6-diiodobenzaldehyde derivatives that is scalable, general in scope, and indeed difficult to be made by other means.