Ethynyl carbonium ions. 3. Diene synthesis with 4-phenylethynylpyrylium salts
Norbornadiene derivatives of pyrylium salts were obtained for the first time by [4+2] cycloaddition of cyclopentadienes and 2,6-diaryl-4-phenylethynylpyrylium salts with and without methyl groups in the 3 and 5 positions. Their photochemical transformations were studied.