Decarboxylative trichloromethylation of aromatic aldehydes and its applications in continuous flow

Two new protocols for the efficient synthesis of 2,2,2-trichloromethylcarbinols, starting from aromatic aldehydes, have been developed. A combination of sodium trichloroacetate in the presence of malonic acid proved efficient for the transformation of electron deficient aldehydes using DMSO as solvent. Electron-rich aldehydes did, however, not require the addition of malonic acid, affording the desired 2,2,2-trichloromethylcarbinols without a trace of the competing Cannizzaro reaction. Finally, the reaction of sodium trichloroacetate in THF with a mixture of aldehyde and malonic acid dissolved in DMSO allowed the protocol to be performed in continuous flow. By performing this decarboxylative reaction in continuous flow, scale-up of the reaction could be achieved with a simple and safe setup. In this flow setup, four electron-deficent aldehydes were successfully transformed into their 2,2,2-trichloromethylcarbinol derivatives on a 100 mmol scale.