Decarboxylation / Elimination type reaction
This type of reaction falls into the category of Grob fragmentation  [Wikipedia]. Conceptually, it is very similar to an E2 mechanism, where an anti-periplanar pair of electrons flows into the sigma anti-bonding orbital of a carbon-leaving group bond resulting in a new pi bond and cleavage of the carbon-leaving group bond. The primary difference between these two is that in an E2, that anti-periplanar pair of electrons comes from deprotonation, and in a Grob fragmentation, the electrons are from breaking some other sigma bond other than a C-H bond.



A syn-oriented version of this reaction can be seen in the generation of benzyne.



Also, decarboxyation is very common with a beta-carbonyl group. This doesn't exactly follow the Grob pattern, because there is no leaving group. The carbonyl plays the role of electron sink.