Substituted anthracene derivatives. Part VII. An examination of some naphthacene endooxide derivatives

High‐Yielding Synthesis and Full Spectroscopic Characterization of 5,6:11,12‐Di‐o‐phenylenetetracene and Its Synthesis Intermediates

“…The combination of both gives the title compound in high yield, without utilizing any transition-metal catalyst. Additionally, we have been able to confirm some long-standing assumptions [30,[39][40][41] concerning the intermediates obtained en route to the title molecule, putting those earlier speculations on solid experimental ground.…”

“…Its molecular structure is in full agreement with the principle of maximum accumulation of π electrons of unsaturated centers in the activated complex. [43] Subsequent acidic de-epoxidation of 3 following the protocol of Badger and Pearce [40] afforded the product 4 only in low Figure 2. Top: ORTEP plot of the molecular structure of the endo isomer of 5,12-diphenyl-5,12-epoxy-5a,11a-dihydrotetracene-6,11-dione ("Bergmann"s compound", 3).…”

“…A facile separation of both compounds was achieved by fractional crystallization from hot n-butyl acetate. In addition to the original routes of Dufraisse, [30] Yagodkin, [41] and Badger and Pearce, [40] Paraskar et al [44] in 2008 presented a promising alternative approach to 4 to which our attention was drawn.…”

“…[42] Even with an optimized synthesis of the dihydroxy intermediate, which was reported by Yagodkin et al in 2009, 4 could only be obtained in low yield or low purity. [41] Our first attempts towards the synthesis of DOPT (8) thus concentrated on the protocols of Bergmann [39] and Badger and Pearce and co-workers [40] starting from 1,3-diphenylisobenzofuran (1) and 1,4-naphthoquinone (2), and included the full characterization of this reported reaction sequence for the first time. [39,40] Isolation of the accessible Diels-Alder compound 5,12-diphenyl-5,12-epoxy-5a,11a-dihydrotetracene-6,11-dione ("Bergmann's compound", 3) [38] in a hitherto unreported quantitative yield was achieved by using diethyl ether as solvent.…”

“…Complete schematic overview of the most important reaction sequences towards 8 from intermediate 4. The initial routes of Dufraisse [30] and Bergmann [39] were confirmed by characterizing the intermediate reaction products completely and were further developed by the protocols of Badger and Pearce, [40] Yagodkin, [41] and Paraskar [44] and their co-workers. Our successful final route to DOPT is shown in the box.…”