C-H Activation to Make Highly Functionalized Anthracenes

Significance

The authors present the tetraarylation of anthraquinone using ruthenium-catalyzed C-H bond activation. The products of the arylation can then be converted into acenes using known methods, arriving at the tetra- or even hexa-substituted anthracene derivatives. The scope of the arylation is remarkable, with electron-poor and electron-rich aryl rings being viable substrates. The proposed mechanism of the arylation is shown above and consists of oxidative cleavage of the aryl C-H bond by ruthenium(0) (A), followed by hydrometalation of pinacolone (B). Transmetal-ation (C) with the arylboronic ester followed by reductive elimination (D) provides the arylation product and regenerates the active ruthenium catalyst.