Selective preparation of polycyclic aromatic hydrocarbons. Part 5.1 Bromination of 2,7-di-tert-butylpyrene and conversion into pyrenoquinones and their pyrenoquinhydrones

Publisher Website
Google Scholar
Abstract
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 and 73% yield, respectively. On the other hand, when the same reaction was carried out with 6.0 mol equiv. of bromine in the presence of iron powder, an acid-catalysed rearrangement of bromine atoms was observed to give 4,5,9,10-tetrabromo-2,7-di-tert-butylpyrene 4 in 90% yield. The same orientation in the chlorination of substrate 1 was also observed to afford 2,7-di-tert-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 reaction of compound 4 with sodium methoxide in the presence of copper(I) iodide, followed by demethylation of the corresponding 4,5,9,10-tetramethoxy derivative 12 with boron tribromide. The strong charge-transfer complex of tetraone 15 and its hydroquinone 13 was observed as being due to the pyrene skeleton. The mechanism of the above novel bromination is also discussed.

This publication has 0 references indexed in Scilit: