Database survey

A search of the Cambridge Structural Database (Version 5.38, update November 2016; Groom et al., 2016) for the substructure of 2-(alkylamino)-4-(alkylimino)naphthalen-1(4H)-one yielded 3 hits (we did not restrict the bonds types to the mayor tautomer). Two of the structures, ESOFID (Schweinfurth et al., 2016) and UDAZEF (Singh et al., 2007) use aromatic amines [aniline or substituted aniline] as the amine moiety. Only one structure, UDAZIJ (Singh et al., 2007), uses an aliphatic primary amine (n-butylamine) in the positions 2 and 4. UDAZIJ is noteworthy because the intramolecular N-H•••O bond is 2.34 (2) Å, much longer than compound (I), and that in the crystal lattice of UDAZIJ a dimeric assembly forms held together by intermolecular hydrogen bonding interactions between the N-H and carbonyl of adjoining molecules.

Synthesis and crystallization

The synthesis of the title compounds were based on new procedures  (complete publication in progress). 
General procedure for the synthesis of the title naphthoquinone compounds. Representative procedure for 2-(adamantan-1-ylamino)-3-chloronaphthalene-1,4-dione. 227 mg (1.00 mmol) of 2,3-dichloronaphthalene-1,4-dione, 166 mg (1.10 mmol, 1.1 equiv) of adamantan-1-amine, and 280 mg (2.00 mmol, 2 equiv) of K2CO3 were dissolved in tert-amyl alcohol (4.0 mL). This solution was stirred at 393 K under a nitrogen atmosphere for 4 h. After being allowed to cool to room temperature, the resultant dark-red solution was diluted with saline water (30 mL) and extracted with methyl tert-butyl ether (3 x 20 mL). The combined organic layers were dried over NaSO4, filtered, and then concentrated under reduced pressure to yield 350 mg of the pure product (94% yield) as a reddish-orange solid. Part of the purified product was redissolved in methanol and placed at room temperature for slow evaporation. After several days, red crystal plates suitable for X-ray analysis were obtained. M.p. 412 K using a Fisher–Johns melting point apparatus with calibrated thermometer. 1H-NMR (600 MHz, CDCl3) δ 8.12-8.13 (dd, = 7.2, 1.2 Hz, 1 H), 8.02-8.04 (dd,= 7.8, 0.6 Hz, 1 H), 7.69-7.72 (td, = 7.8, 1.8 Hz, 1 H), 7.61-7.64 (td, = 7.8, 1.2 Hz, 1 H), 5.92 (br. s., 1 H), 2.17 (br. s., 3 H), 2.15 (s, 6 H), 1.71 (br. s., 6 H).  
2-(adamantan-1-ylamino)-3-bromonaphthalene-1,4-dione. 316 mg (1.00 mmol) of 2,3-dibromonaphthalene-1,4-dione, 166 mg (1.10 mmol, 1.1 equiv) of adamantan-1-amine, and 280 mg (2.00 mmol, 2 equiv) of K2CO3 dissolved in tert-amyl alcohol (4.0 mL) gave 381 mg of the pure product (98% yield) as a red solid. The reaction solution was stirred at 393 K under a nitrogen atmosphere for 24 h. Part of the purified product was redissolved in acetonitrile and placed at room temperature for slow evaporation. After several days, red crystal plates suitable for X-ray analysis were obtained. M.p. 427 K using a Fisher–Johns melting point apparatus with calibrated thermometer. 1H-NMR (600 MHz, Chloroform-d) δ 8.11 (dd, J = 7.7, 1.4 Hz, 1H), 8.02 (dd, = 7.7, 1.4 Hz, 1H), 7.69 (td, J = 7.5, 1.4 Hz, 1H), 7.64 (td, J = 7.5, 1.4 Hz, 1H), 5.65 (br. s, 1H), 2.17 (br. s, 3H), 2.12 (m, 6H), 1.77 – 1.65 (m, 6H).

Refinement details

Crystal data, data collection and structure refinement details are summarized in Table X. All hydrogen atoms are placed in calculated positions [C—H = 0.98–0.99 Å; U iso(H) = 1.2 or 1.5U eq(C)]. 
Acknowledgements
The Centro de Investigaciones en Productos Naturales (CIPRONA), the Centro de Electroquímica y Energía Química (CELEQ) and the Escuela de Química, Universidad de Costa Rica (UCR) provided support.