<p>Ring systems in
pharmaceuticals, agrochemicals and dyes are ubiquitous chemical motifs. Whilst
the synthesis of common ring systems is well described, and novel ring systems
can be readily computationally enumerated, the synthetic accessibility of
unprecedented ring systems remains a challenge. ‘Ring Breaker’ enables the
prediction of ring-forming reactions, for which we have demonstrated its
utility on frequently found and unprecedented ring systems, in agreement with
literature syntheses. We demonstrate its performance on a range of ring
fragments from the ZINC database and highlight its potential for incorporation
into computer aided synthesis planning tools. Additionally, we generate a
multi-label dataset using bipartite reaction graphs on which we train ‘Ring Breaker’
to model the relationship between one ring fragment and the multiple reactions
recorded for its synthesis in the dataset; we thereby overcome the single-label
approaches previously used. These approaches to ring formation and
retrosynthetic disconnection offer opportunities for chemists to explore and
select more efficient syntheses/synthetic routes. </p>
Reaction graphs of double Fano planes