Efficient Synthesis of Bis(dibromomethyl) arenes as Important Precursors of Synthetically Useful Dialdehydes

This work presents an efficient synthesis of bis(dibromomethyl) benzenes and a bis(dibromomethyl) thiophene as precursors of aromatic dialdehydes by bromination of dimethyl-substituted arenes under various reaction conditions (yields up to 99%). Several new variants of this reaction, including the use of N-bromosuccinimide (NBS) and bromine, and various solvents to replace carbon tetrachloride, benzene and carbon disulfide, were also tested. In the optimised protocols, the inconvenient solvents were replaced by 1,2-dichloroethane (DCE) and/or acetonitrile. In the DCE protocols, we reduced reaction times 24-32-fold, reduced the amount of NBS a fewfold and lowered power consumption relative to the literature protocols. The procedures also allowed elimination of long-lasting incandescent irradiation (100500 W). The replacement of NBS by bromine led to a further reduction in the amount of brominating agent. The obtained bromo derivatives were efficiently converted into the corresponding dialdehydes (90-96%), which in turn are useful in materials chemistry.