We show how fast semiempirical QM methods can be used to decrease the computational requirements for automated reaction mechanism discovery, using two different method for generating reaction intermediates: graph-based systematic enumeration of all possible products developed by Kim et al. and the meta-dynamics based method by Grimme. We test the two approaches on the reactions of 3hydroperoxypropanal, which have been studied by a large variety of reaction discovery approaches and therefore provides a good benchmark. Our aim is the find the three reactions with barriers below 50 kcal/mol (Figure ).