Is RCOOH + H2SO4 + heat a viable alternative to RCOCl + AlCl3 in Friedel-Crafts acylation?

Can concentrated strong acid like H₂SO₄ be used to protonate a carboxylic acid to RC(OH)₂⁺, forming RCO⁺ by removal of H₂O, analogous to the reaction with nitric acid to produce nitronium?


Would this be a viable way of acylating an aromatic compound?




Sure it is possible.


It is best known for intramolecular cyclisation using Polyphosphoric Acid (PPA) or Methanesulfonic acid [more here](https://www.masterorganicchemistry.com/2018/05/30/intramolecular-friedel-crafts-reactions/).


Examples are known of intermolecular Friedel-Craft acylation using strong acid on a carboxylic acid substrate - PPA is used in this [example](https://onlinelibrary.wiley.com/doi/epdf/10.1002/chin.200642083)


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