Fe3+-doped K10 montmorillonite combined with 2,6-di-tert-butyl-4-methyl-phenol is a potent catalytic system for trans-2-methylene-1,3-dithiolane 1,3-dioxide as a dienophile. Cycloaddition occurs with cyclopentadiene and furan as a diene at room temperature in short time and with good yields (64% overall).