Organocatalyst for Photocatalytic Esterification

Diisopropyl hydrazine-1,2-dicarboxylate (1) is known byproduct of Mitsunobu reaction’s when using diisopropyl azodicarboxylate; however, it can be utilized as a catalyst for photoesterification. In the presence of catalytic amount of 1 and the flavin derivative TARF³-CH₃ under an oxygen atmosphere, carboxylic acids and alcohols will react to afford ester products, typically in good yields via irradiation with 450 nm of light. When these conditions are applied to secondary alcohols, the products are given with stereoretention. This transformation can be seen as complementarily to the conventional Mitsunobu reaction, expanding versatility.