SELECTIVE PREPARATION OF POLYCYCLIC AROMATIC-HYDROCARBONS .5. BROMINATION OF 2,7-DI-TERT-BUTYLPYRENE AND CONVERSION INTO PYRENOQUINONES ANDTHEIR PYRENOQUINHYDRONES

The bromination of 2,7-di-tert-butylpyrene 1 with 1.1 mol equiv. and 2 .2 mol equiv. of bromine in a carbon tetrachloride solution afforded 1 -bromo-2,7-di-tert-butylpyrene 2a and a mixture of 1,6-dibromo(3a) and 1,8-dibromo-2,7-di-tert-butylpyrene (3b) in 85 land 73% yield, respec tively. On the other hand, when the same reaction was carried outwith 6.0 mol equiv. of bromine in the presence of iron powder, an acid-cata lysed rearrangement of bromine atoms was observed to give 4,5,9,10-tet rabromo-2,7-di-tert-butylpyrene 4 in 90% yield. The same orientation i n the chlorination of substrate 1 was also observed to afford 2,7-di-t ert-butyl-1-chloropyrene 2b. The conversion of tetrabromide 4 into 2,7 -di-tert-butylpyrene-4,5,9,10-tetraone 15 was carried out by the react ion of compound 4 with sodium methoxide in the presence of copper(I) i odide, followed by demethylation of the corresponding 4,5,9,10-tetrame thoxy derivative 12 with boron tribromide. The strong charge-transfer complex of tetraone 15 and its hydroquinone 13 was observed as being d ue to the pyrene skeleton. The mechanism of the above novel brominatio n is also discussed.