Unusual 1,1‐Dicarboxylation Selectivity in the Domino Hydrocarboxylation of Alkynes with Formate and Application in Polyimide Photoresists

We report for the first time a photoinduced domino 1,1-dicarboxylation of alkynes for the synthesis of malonic acid derivatives using a cesium formate solution (80% w/w in water), which is different from previous 1,2-dicarboxylation methods that usually produce succinic acids. Cesium malonate precipitated directly from the diluted reaction mixture and was collected by filtration without further purification. Interestingly, solid cesium formate with additional water led to a mono-carboxylation product. The solubility of cesium formate and alkaline environment are two key factors contributing to the outcome. A series of malonic acids, propionic acids and drug intermediates were synthesized by the methods in good yields. Mechanism experiments and DFT calculations indicate that the malonic acid is formed through the α-selective addition of CO₂ ^•- to a cinnamate intermediate. This method enables direct preparation of water-soluble carboxylate-functionalized molecules and polymers from hydrophobic alkyne-containing precursors, showing potential usability in photolithography for semiconductor manufacturing.