Selective Preparation. 30. A Convenient Preparation of 5,13-Di-tert-butyl-8,16-disubstituted-metacyclophanes and Their Trans-tert-butylation and Halogenation Reactions

Article abstract of DOI:10.1021/jo00321a005

The preparation of 5,13-di-tert-butyl-8,16-disubstituted-<2.2>metacyclophanes (16a-k) from the corresponding 4-substituted-tert-butylbenzenes was described.The AlCl3-CH3NO2-catalyzed trans-tert-butylation of 5,13-di-tert-butyl-8,16-dimethyl<2.2>metacyclophane (16b) in benzene afforded 8,16-dimethyl<2.2>metacyclophane (28a) in good yield.However, the similar reaction of diethyl derivative 16c gave only a complex mixture of products.Treatment of 16b and 28a with NBS in CCl4 afforded the corresponding dibromides 38 and 39 in 86percent and 95percent yields, respectively.The bromination of 16b and 16c with bromine in CCl4 afforded the corresponding anti-10b,10c-dialkyl-4,5,9,10-tetrabromo-2,7-di-tert-butyl-10b,10c-dihydropyrenes 41a and 41b in good yields, respectively.However, it was also found that the bromination of 16b and 16c in the presence of Fe powder in the same solvent afforded 4,5,9,10-tetrabromo-2,7-di-tert-butylpyrene (40) in good yield in all cases.On the other hand, the bromination of 28a with bromine in the presence of Fe powder gave 2,7-dimethyl-3,6,8,11-tetrabromo-4,5,9,10-tetrahydropyrene (42).The reaction pathway of the bromination of 16 is discussed.