Brønsted-acidic ionic liquids as efficient catalysts for the synthesis of polyoxymethylene dialkyl ethers

Polyoxymethylene dialkyl ethers (RO(CH2O)nR, n ≥ 1) were synthesized by acetalation of formaldehyde with dialkyl formal or aliphatic alcohol using efficient, recyclable Brønsted-acidic ionic liquids as catalysts; excellent yields and selectivities were obtained under solvent-free conditions.