In the 2nd, we’d attract an arrow that shows the set of electrons through the C–C bond relocating from the CO2H and towards the carbon adjacent to the C=O. A further context in which decarboxylation arrives up is in retro Diels-Alder reactions of pyrones. Cure of pyrones using a dienophile https://thca-guides23333.bloguetechno.com/the-cbda-cannabidiolic-acid-diaries-67974812