Elbs reaction

What is Elbs reaction?

The thermal decomposition of o-methylbenzophenones was previously studied by Behr and van Dorp in 1873 and Ador and Rilliet in 1878, but it was Elbs who extensively investigated and developed this reaction, which is now known as the Elbs reaction or Elbs pyrolysis.

Elbs reaction - general reaction scheme - Elbs pyrolysis
Elbs reaction

The Elbs reaction involves intramolecular condensation of diaryl ketones with a methyl or methylene substituent ortho to the carbonyl group, leading to the preparation of polyaromatics, particularly anthracene. This reaction is usually carried out by high-temperature pyrolysis without the need for a solvent or catalyst, and sometimes accompanied by the elimination of substituents like fluoro, methyl, and methoxy.

However, this method may not be ideal for preparing polyaromatics with substituents, although it is the fastest and most cost-effective method for synthesizing parent polyaromatics. The Elbs reaction is thought to involve hydrogen transfer, and the yield can be improved by periodically removing the formed anthracene derivatives from the reaction zone.