Protonation of diarylacetylenes in superacid HSO3F and their oxidation in the HSO3F/PbO2 system: One-pot synthesis of polysubstituted naphthalenes

摘要

In the superacid HSO3F, diarylacetylenes bearing one electron-withdrawing group (NO2, CN, COMe, CO2Me) in each arene ring form stable ions, protonated at these groups. Oxidation of such diarylacetylenes in the HSO3F/PbO2 system at -75 to -50 degrees C over 2-2.5 h, followed by quenching of the reaction mixture with hydrochloric (or hydrobromic) acid at -60 to 25 degrees C, resulted in the formation of (E,E)-1,4-dichloro (or dibromo)-1,2,3,4-tetraarylbuta-1,3-dienes. These butadienes spontaneously undergo electrocyclic transformation into polysubstituted naphthalenes at room temperature. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).