TREATMENT OF DIMETHOXYPARACYCLOPHANES WITH AMMONIUM CERIUM(IV) NITRATE

The treatment of dimethoxy[n]paracyclophanes (n=7-12) (5), [2]paracyclo[2]thiophenophane (13), and dimethoxy[2.2]paracyclophane (8) with CAN in MeCN-water afforded 2,4-cyclohexadien-1-ones 9, [8]paracyclophanedione 10, the ring-opened esters 11, and ketones 12. When the n value of 5 was 7, 8, or 9, rearrangement of the methylene bridge occurred and 9 was obtained as the main products. With the n value of 12, quinone 10 was the main product. Whereas, treatment of 13 with CAN afforded the ring-opened ester 14 as the sole product. These results show that formation of 9 is dependent on the strain of the paracyclophanes. Epoxide A was proposed as an intermediate of these reactions.