Could an ester react with magnesium oxide?
Magnesium oxide can be an effective catalyst in transesterification reaction of vegetable oil samples mostly containing high carbon esters: 


$\ce{MgO}$ is used as catalyst to increase the rate of transesterification reaction of sunflower oil in supercritical methanol.
The reaction in case of soybean oil has also been reported. This method was developed using metal-chitosan complex leading to higher yield of fatty acids and ethyl ester (biodiesel).
Sometimes alkaline supported catalyst like $\ce{MgO-K2CO3}$ ($\ce{K2CO3}$ fused $\ce{MgO}$) has also been used in the transesterification reaction of canola oil.


Another reaction using magnesium oxide as catalyst is the carbon-acylation of malonates with either acyl chlorides or chloroformates. Various malonic esters (methyl, ethyl, isopropyl and isobutyl) were easily alkoxycarbonylated to give the corresponding methanetricarboxylic esters. 



References (in the order of mentioned points)


A. Demirbas, "Biodiesel from Vegetable Oils with MgO Catalytic Transesterification in Supercritical Methanol" Pages 1645-1651, 22 Jul 2008 DOI: https://doi.org/10.1080/15567030701268401
Gizelle I. Almerindoa, Luiz F., D.Probsta Carlos E. ,M. Campos Rusiene , M.de Almeidac , Simoni M. P.Meneghettic, Mario R.Meneghettic , Jean-Marc Clacens, Humberto V.Fajardoe "Magnesium oxide prepared via metal–chitosan complexation method: Application as catalyst for transesterification of soybean oil and catalyst deactivation studies" Journal of Power Sources Volume 196, Issue 19, 1 October 2011, Pages 8057-8063 DOI: https://doi.org/10.1016/j.jpowsour.2011.05.030
http://www.asianjournalofchemistry.co.in/User/ViewFreeArticle.aspx?ArticleID=28_2_6
Jacek Skarżewski "Carbon-acylations in the presence of magnesium oxide. A simple synthesis of methanetricarboxylic esters"Tetrahedron Volume 45, Issue 14, 1989, Pages 4593-4598 DOI: https://doi.org/10.1016/S0040-4020(01)89094-3