  The task of searching through patent documents is crucial for chemical patent
recommendation and retrieval. This can be enhanced by creating a patent
knowledge base (ChemPatKB) to aid in prior art searches and to provide a
platform for domain experts to explore new innovations in chemical compound
synthesis and use-cases. An essential foundational component of this KB is the
extraction of important reaction snippets from long patents documents which
facilitates multiple downstream tasks such as reaction co-reference resolution
and chemical entity role identification. In this work, we explore the problem
of extracting reactions spans from chemical patents in order to create a
reactions resource database. We formulate this task as a paragraph-level
sequence tagging problem, where the system is required to return a sequence of
paragraphs that contain a description of a reaction. We propose several
approaches and modifications of the baseline models and study how different
methods generalize across different domains of chemical patents.
