Synthesis of Precursors for the Pyrolytic Formation of Pentatetraenones

Abstract

3-(9′,10′-Dihydro-9′,10′-ethanoanthracen-11′-ylidene)prop-2-enoyl chloride and its [12′,12′- 2 H₂] and [1- ¹³ C] isotopomers have been prepared and pyrolysed. Argon matrix infrared spectroscopy showed ν₂ bands at 2207 . 7, 2207 . 0, and 2168 . 5 cm⁻¹ respectively for the three pentatetraenone isotopomers. The pyrolysate of the 12′-methyl substituted precursor showed a band at 2205 cm⁻¹ which was tentatively assigned to methylpentatetraenone. The 12′-ethenyl substituted precursor gave a pyrolysate showing ketene bands but also yielded 9,10-dihydro-9,10[1′,2′]-benzenoanthracene.