Key points are not available for this paper at this time.
The direct oxidative coupling of phenylazoles with internal alkynes proceeds efficiently in the presence of a rhodium catalyst and a copper oxidant accompanied by double or quadruple C-H bond cleavages. Thus, as a representative example, 4,5-diphenylpyrazolo1,5-aquinoline, 1-(1,2,3,4-tetraphenylnaphthalen-5-yl)pyrazole, and 1-(1,2,3,4,5,6,7,8-octaphenylanthracen-9-yl)pyrazole can be obtained selectively through the coupling of 1-phenylpyrazole and diphenylacetylene in 1:1, 1:2, and 1:4 manners, respectively. The reactions preferentially take place at the electron-deficient sites on the aromatic substrates. A comparison of reactivities of variously substituted and deuterated substrates sheds light on the mechanism of C-H bond cleavage steps. The reaction pathway is highly dependent on reaction conditions employed, especially on the nature of solvent. The influence of solvation of a key rhodacycle intermediate has been investigated computationally. In addition, some of the condensed aromatic products have been found to exhibit intense fluorescence in the solid state.
Umeda et al. (Wed,) studied this question.