Reaction of Guaiazulene with Bromine in Hexane and in Aqueous Tetrahydrofuran

Article abstract of DOI:10.1246/cl.1995.687

2-Bromoguaiazulenium bromide and 3,3-dibromo guaiazulenium bromide were obtained respectively from the reaction of guaiazulene and its 3-bromo compound with 1 equivalent of bromine in hexane at -20 deg C.The former compound afforded in methanol a mixture of guaiazulene, 3,3'-biguaiazulene, and oligomers, and gave 3-bromoguiazulene quantitatively with alkali.Dibromoguiazulenium bromide afforded with further moles of bromine in aqueous THF a mixture of guaiazulenequinone, 3-bromo-1-hydroxyquaiazulen-5-one, and a dark blue solid A in different ratios depending on the reaction conditions.