In the crystal structure of 8, three crystallographically independent molecules are present in the asymmetric unit. During the refinement, the i Pr group of one molecule was found to be disordered over two orientations with the site occupancy factors refined as 0.527(6) and 0.473 (6), respectively. The O-atom of a C=O group of a second molecule was also disordered over two positions with site-occupancy factors of 0.746(9) and 0.254 (9). Similarity restraints were applied in SHELXL to the bond distances in the disordered parts using the SADI instruction, and to the displacement parameters of the disordered atoms using the SIMU instruction. The H-atoms on the N-atoms were located in a difference Fourier map, and were freely refined (positions and isotropic displacement parameters). All remaining H-atoms were placed geometrically and refined isotropically using a riding model, with C-H = 0.95 Å (C-aromatic), 0.98 Å (C-methyl), 0.99 Å (C-methylene) and 1.00 Å (C-methine), in association with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(C-methyl). CCDC-2430253 (2) and CCDC-2430253 (8) contain the supplementary crystallographic data for this paper. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures.