Benzocyclobutene-1-carboxylic acid methyl ester

Methyl bicyclo[4.2.0]octa-1,3,5,7-tetraene-7-carboxylate

1,2-Dihydrobenzocyclobutene-1-carboxylic acid methyl ester

Bicyclo[4.2.0]octa-1,3,5-triene-7-carboxylic acid methyl ester