9-Chloro-10-nitro-9,10-dihydroanthracene: Improved Synthesis, Halogen Exchange to the 9-Bromo and 9-Iodo Analogues, and Kinetics of Ag(I)-Mediated Conversion to 9-Nitroanthracene and 9-Aminoanthracene

9-Chloro-10-nitro-9,10-dihydroanthracene (anthracene nitrochloride, ANC), the intermediate of the Organic Syntheses route to 9-nitroanthracene (9-NA), was prepared on a 50 g scale in 93% yield with a stoichiometric amount (0.98 equiv) of 63% nitric acid in glacial acetic acid at 30–35 °C, followed by trapping with HCl/AcOH at 5–10 °C. Base-mediated dehydrochlorination gave 9-NA in 91% overall yield (Organic Syntheses: 60–68%). Finkelstein exchange of ANC with NaBr or NaI in acetone afforded the previously unreported 9-bromo- (NBDA, 96%) and 9-iodo-10-nitro-9,10-dihydroanthracene (NIDA, 98%). The structures of ANC, NBDA and NIDA were established by elemental analysis and quantitative Ag(I)-mediated dehalogenation, and confirmed by FTIR and 1H and 13C NMR spectroscopy. The nitro-bearing carbon C-10 stays at δC 85.5–86.3, whereas the halogen-bearing carbon C-9 moves from 56.5 (Cl) to 49.2 (Br) and 32.4 ppm (I) owing to the heavy-atom effect, confirming exchange at C-9. ANC reacts with AgNO3 instantaneously at room temperature, whereas NBDA and NIDA are converted to 9-NA in AgNO3-saturated acetone at 30 °C with pseudo-first-order kinetics (kobs = 1.55 ± 0.02 and 1.73 ± 0.02 h−1, respectively). The much higher reactivity of the chloride is contrary to the normal leaving-group order; it is discussed in terms of the multi-step mechanism of the conversion, in which C–X heterolysis is not necessarily rate-determining. Reduction of 9-NA with Zn/HCl gave 9-aminoanthracene in 88% yield.