SYNTHESIS OF 2,3-DISUBSTITUTED-BENZOBARRELENES 2,5-DISUBSTITUTED-BENZOBARRELENES AND 2,6-DISUBSTITUTED-BENZOBARRELENES HIGH-TEMPERATURE BROMINATION .2.

Bromination of 2-bromo-1,4-dihydro-1,4-ethenonaphthalene (7) at -0-degrees-C has been found to give five rearranged tribromides 8, 9, 10, 11, and 12 via Wagner-Meerwein rearrangement with accompanying aryl and alkyl migration. It has been shown that the endo tribromides 9 and 11 are secondary products formed by bromine-catalyzed reaction of the corresponding exo tribromides. The bromination of 7 at 78-degrees-C resulted in the formation of the non-rearranged products 21, 22, 23, and 24 with bicyclo-[2.2.2]skeleton. The structure of 8, 10, 11 and 21 have been determined by X-ray structural analysis. The dehydrobromination of the tribromides 21, 22, 23, and 24 with potassium tert-butoxide provided the corresponding benzobarrelenes 2a, 3a, and 4a in high yield. Reaction of dibromobenzobarrelenes with CuCN resulted in the formation of dicyano derivatives 2b, 3b, and 3b. Reaction of 3a with BuLi and subsequent quenching with MeI afforded dimethyl derivative 3c.