Synthesis of Acridines through Alkyne Addition to Diarylamines.

A new synthesis of substituted acridines is achieved by palladium-catalyzed addition of terminal acetylenes between the aryl rings of bis(2-bromophenyl)amine. By including a diamine base and elevating the temperature, the reaction pathway favors the formation of acridine over a double Sonogashira reaction to form bis(tolan)amine. This method is demonstrated with several aryl-alkynes and alkyl-alkynes.

Diels-Alder cycloaddition of acetylene gas to a polycyclic aromatic hydrocarbon bay region.

The direct conversion of a polycyclic aromatic hydrocarbon bay region to a new, unsubstituted benzene ring by Diels-Alder cycloaddition of acetylene gas is reported for the first time. At 140 °C in dimethylformamide, under 1.8 atm pressure of acetylene gas, 7,14-dimesitylbisanthene is slowly converted to 7,14-dimesitylbenzo[ghi]bisanthene (21% conversion in 48 h).

Facile air-oxidation of large aromatic hydrocarbon bay regions to bay region quinones: predicted oxygen-sensitivity of hydrogen-terminated carbon nanotubes.

Dimesitylbisanthene (1) oxidizes to the corresponding bay region quinone (2) on standing in solutions exposed to air and ambient light. It is anticipated that hydrogen-terminated carbon nanotubes with bay regions on the rim are likely to exhibit even greater sensitivity toward air oxidation.

Diels-Alder reactivity of polycyclic aromatic hydrocarbon bay regions: implications for metal-free growth of single-chirality carbon nanotubes.

A soluble bisanthene derivative, 4,11-dimesitylbisanthene, has been synthesized in three steps from bianthrone. In hot toluene, this bisanthene undergoes a clean Diels-Alder reaction with diethyl acetylenedicarboxylate to give a rearomatized 1:1 cycloadduct and, more slowly, a rearomatized 2:1 cycloadduct. In a competition experiment with the shorter "periacene" perylene, only the bisanthene reacts, and the perylene remains unchanged. The experimental results stand in complete accord with density functional calculations (B3LYP/6-31G*), which predict that the activation energies for Diels-Alder cycloadditions in the bay regions of periacenes should diminish monotonically as the length of the molecule increases. This structure-activity relationship offers hope that single-chirality carbon nanotubes can be grown from suitable hydrocarbon templates, without metal catalysis, by a Diels-Alder cycloaddition/rearomatization strategy, using acetylene or a "masked acetylene" as the dienophile.