Template based retrosynthesis has its roots in the first approaches to Computer Assisted Synthesis Planning (CASP) by Corey. More recently, the works of Segler and Waller, and Coley et. al. have pioneered this approach, coupling it with neural networks. This approach has been utilized in 'Ring Breaker' for the prediction of ring formations in the retrosynthetic direction. Starting from reaction data, namely Reaxys® † and the publicly available US Patent Office extracts (USPTO) which describe the relationship between reactants, reagents and products. The reaction center is extracted, the so-called reaction template or rule. The reaction template describes the atoms and bonds changing in the reaction, and captures all changes occurring one bond away from the atoms involved in the reaction center. This can be viewed as a generalized form of the overall reaction from which the template was extracted.