Synthesis of syn-3a(12c),9a(9b)-dihomoperylene-3,10-dione, (E)-syn-2,2 '-bi(7H-1,6-methano[10]annulenylidene)-7,7 '-dione and of its rearrangement product, trans-12a,12b-dihydro-3a(12c),9a(9b)-dihomoperylene-3,10-dione

The main objective of the present work was to evaluate the synthesis of 1,6 -methano[10]annulene derivatives of perylene and perylene-3,10-dione. The s tarting material for the synthetic sequence was 2,7-dibromo-1,6-methano[10] annulene (I), which was converted by methoxy- and ethoxy-debromination SNAr -type reactions to 2-bromo-7-methoxy- and -7-ethoxy-1,6-methano[10]annulene s (II). The reactions were much more facile than those of the apparently si milar halogenonaphthalenes. Compounds II were reductively coupled, using a Ni(0) complex, to give isomeric mixtures of rac- and meso-7,7-dimethoxy- an d -diethoxy-2,2'-bi(1,6-methano[10]annulenyl)s (IIIA and IIIB). Oxidative c oupling of a mixture of compounds IIIA and IIIB with thallium(III) trifluor oacetate in acetonitrile gave (E)-syn-2,2'-bi(7H-1,6- methano[10]annulenyli dene)-7,7'-dione IV as the main reaction product, accompanied by a small am ount of syn-3a(12c),9a(9b)-dihomoperylene-3,10-dione, VI. Subsequent experi ments showed that the meso-form (IIIB) produced the syn-dihomoperylenedione (VI); while the rac-form (IIIA) gave (E)-syn-2,2'- bi(7H-1,6-methano[10]an nulenylidene)-7,7'-dione IV. The low yield of the dihomoperylenedione sugge sts decomposition reactions occur, with various by-products remaining undet ected. A solution of the annulene-quinone (IV) in carbon tetrachloride, whe n refluxed and illuminated rearranged to give trans-12a,12b-dihydro-3a(12c) ,9a(9b)-dihomoperylene-3,10-dione (V).