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

Abstract

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 starting material for the synthetic sequence was 2,7-dibromo-1,6-methano[10]annulene (I), which was converted by methoxy- and ethoxy-debromination S_NAr-type reactions to 2-bromo-7-methoxy- and -7-ethoxy-1,6-methano[10]annulenes (II). The reactions were much more facile than those of the apparently similar halogenonaphthalenes. Compounds II were reductively coupled, using a Ni(0) complex, to give isomeric mixtures of rac- and meso-7,7-dimethoxy- and -diethoxy-2,2′-bi(1,6-methano[10]annulenyl)s (IIIA and IIIB). Oxidative coupling of a mixture of compounds IIIA and IIIB with thallium(III) trifluoroacetate in acetonitrile gave (E)-syn-2,2′-bi(7H-1,6-methano[10]annulenylidene)-7,7′-dione IV as the main reaction product, accompanied by a small amount of syn-3a(12c),9a(9b)-dihomoperylene-3,10-dione, VI. Subsequent experiments 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]annulenylidene)-7,7′-dione IV. The low yield of the dihomoperylenedione suggests decomposition reactions occur, with various by-products remaining undetected. A solution of the annulene-quinone (IV) in carbon tetrachloride, when refluxed and illuminated rearranged to give trans-12a,12b-dihydro-3a(12c),9a(9b)-dihomoperylene-3,10-dione (V).