[JoeyBob]

Im trying to figure out the mechanism for the above and am quite confused. I can find a lot of literature involving lactone formation when a reaction occurs between an alcohol and carboxylic acid group, but have not found anything for a reaction between an alkene and a carboxylic acid group.

I have a mechanism shown here that would give the right product after reacting with a base, but I really doubt that such a reaction would occur, since 2 cations are formed. Intuitively the C=O part of the compound also feels like a better electrophile than the OH, but if this reaction occurred no ester is formed.

The catalysis is amberlyst-15, an acid, but I dont really see how protonation here leads to a lactone. I could see this causing water to leave the compound, but that would give the wrong product.

[chenbeier]

You have to much positive charges. In my opinion the H+ from the carboxyl group attack the double bond and on the second carbon there will a positive charge.  This charge react with negativ charge on  COO- to build the Lacton.

[Orcio_87]

@chenbeier True, but after addition of H⁺ positive charge will located on the first, rather than second carbon atom.

[chenbeier]

Yes it is the first one (Markovnikov), otherwise the product can not be formed.