Investigation of the mechanism of the intramolecular Scholl reaction of contiguous phenylbenzenes.
Two mechanisms of the Scholl reaction were investigated in the series 1, 2, ..., n-oligophenylbenzenes (n = 2, 3, 4, 6) at the B3LYP/6-31G(d) level of theory. A mechanism involving generation of a radical cation followed by C-C bond formation and dehydrogenation is unlikely on the basis of unfavorable energies of activation. A mechanism involving generation of an arenium cation followed by C-C bond formation and dehydrogenation is energetically feasible. An explanation for the facile polycondensation of hexaphenylbenzene to hexa-peri-hexabenzocoronene, where six new aryl-aryl bonds are formed, is provided. Kinetic simulations based on the calculated activation energies of the arenium cation mechanism predict that intermediates will not accumulate; this is supported by mass balance experiments. Reaction optimization studies suggest that PhI(O2CCF3)2/BF3.OEt2 or MoCl5 are superior to FeCl3 or AlCl3/CuCl2. This is a full account of our work reported partially as a communication previously (Rempala, P.; Kroulík, J.; King, B. T. J. Am. Chem. Soc. 2004, 126, 15002-15003).
Rempala
Pawel
P
Department of Chemistry, University of Nevada-Reno, Reno, NV 89557, USA.
Kroulík
Jirí
J
King
Benjamin T
BT
D001555:Benzene Derivatives / Q000138:chemical synthesis* / Q000737:chemistry; D002412:Cations / Q000138:chemical synthesis / Q000737:chemistry; D003198:Computer Simulation; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure
D001555:Benzene Derivatives; D002412:Cations; D005609:Free Radicals