Electrochemical Cyclobutane Synthesis in Flow: Scale-Up of a Promising Melt-Castable Energetic Intermediate

The design of a scalable, safe, and robust route to a promising energetic material containing a cyclobutane and four nitric ester groups is described. This route includes a streamlined preparation of a linear cyclobutane precursor, the use of safe methods for tetraester reduction and nitration, and the translation of a small-scale batch electrochemical oxidative cyclization to forge the cyclobutane to a continuous flow setup capable of producing quantities of more than 100 g in a single run. In principle, this scale was limited only by the space considerations of an academic lab, as a larger reservoir would enable kilogram-scale preparations. Lessons learned from an engineering and reaction optimization standpoint in this electrochemical scale-up are also discussed.