BROMINATION OF EUGENOL DERIVATIVES WITH MOLECULAR BROMINE Budi Arifin (1*), Yana Maolana Syah (1), and Didin Mujahidin (1)
1) Chemistry Study Program, Bandung Institute of Technology
Jalan Ganesha 10, Bandung 40132, Indonesia
*budiarifin2[at]gmail.com
Abstract
Eugenol (4-allyl-2-methoxyphenol) conducts aromatic bromination at C-6 with molecular bromine (Br2), whereas eugenyl benzoate and methyleugenol undergo aromatic bromination at C-5, both preceded by alkene bromination. There is no information yet on the exact composition of bromination products generated from eugenol derivatives employing various Br2 equivalents and phenol protecting groups. Therefore, we present the bromination of eugenol derivatives (eugenyl acetate, eugenyl benzoate, and benzyleugenol) with 1.2, 2.4, and 3.6 equivalents Br2 in chloroform. Bromination with 1.2 equivalents Br2 produces dibromide as an adduct of an alkene double bond in all three derivatives. This is followed by aromatic substitution at C-5 to produce 5-bromo dibromide derivatives with 2.4 equivalent Br2. The dibromide and 5-bromo dibromide derivatives of eugenyl acetate are hydrolyzed promptly during aromatic substitution and undergo additional substitution. As a result, the main products are 5-bromoeugenol dibromide and 6-bromoeugenol dibromide. The brominated acetate esters are no longer evident when 3.6 equivalents Br2 are applied. The benzyl ether begins to cleave as well, but the benzoyl ester is not, implying that this group is more acid resistant. These findings suggest that by utilizing the benzoyl protecting group, a strategy for indirectly substituting the eugenol ring at C-5 could be devised.
