Catalytic β-Bromohydroxylation of Natural Terpenes: Useful Intermediates for the Synthesis of Terpenic Epoxides

Table 4

Influence of the catalyst amount on the bromohydroxylation of 1a.

Entry	Catalyst (g)	Conversion (%)	Yield of 2a (%)
1	0.03	89	67
2	0.04	89	82
3	0.06	81	65
4	0.08	77	61
5	None	60	40

Reaction conditions: 1a 0.4 g, NBS 1.3 equiv., catalyst (Dowex Marathon A, Cl⁻ form), 0.04 g, acetone/H₂O 4 : 1 (v/v), 15 min. Conversion and yield were generally calculated by GC analysis using dodecane as the internal standard.