We have developed metal-free regiocontrolled dehydrogenative C-H/C-H cross-coupling of aryl sulfoxides with phenols by means of trifluoroacetic anhydride. Because the reaction would proceed through an interrupted Pummerer reaction followed by sulfonium-tethered [3,3]-sigmatropic rearrangement, the C-H/C-H coupling takes place exclusively between the ortho positions of both substrates. Various functional groups including carbonyl, halo, siloxy, and even boryl moieties are compatible. The biaryl products naturally possess hydroxy and sulfanyl groups, which allows the products to be useful synthetic intermediates, as evidenced by the syntheses of π-expanded heteroarenes such as unprecedented 7,12-dioxa[8]helicene.

Diphenylphosphine-oxide-fused Ni porphyrin 8 was synthesized from 3,5,7-trichloroporphyrin 5 via a reaction sequence of nucleophilic aromatic substitution with lithium diphenylphosphide, oxidation with H O , and palladium-catalyzed intramolecular cyclization. Reduction of 8 with HSiCl gave diphenylphosphine-fused Ni porphyrin 9. The embedded P=O and P moieties serve as a strong electron-accepting and electron-donating group to perturb the optical and electrochemical properties of the Ni porphyrin. Ni porphyrin 9 is diamagnetic with a low-spin Ni center in solution but becomes paramagnetic with a five-coordinated Ni center with high-spin (S=1) state in the solid state. Diphenylphosphine-oxide-fused Zn porphyrin 10 was also synthesized and shown to form a face-to-face dimer with mutual O-Zn bonds in the crystal and in nonpolar and moderately polar solvents. The dimerization of 10 in CDCl has been revealed to be an entropy-driven process with a large entropy gain (ΔS =207 J K mol ).