The synthesis of ethoxycarbonyl functionalized Tröger's base is accompanied by the formation of a considerable amount of a 3,4-dihydroquinazoline by-product. We found that both compounds can be readily isolated from reaction mixture on a preparative scale by standard crystallization from appropriate solvents.
Kovalenko, V., TUMANOV, N., Vasiutovich, K., & Leyssens, T. (2020). Ethoxycarbonyl functionalized Tröger’s base alongside its congener dihydroquinazoline: A trick with crystallization. Chemical Data Collections, 25, 100339. https://doi.org/10.1016/j.cdc.2020.100339 (Original work published 2020)