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

Table 1

Influence of the catalyst on the bromohydroxylation of 1a.

Entry	Catalyst	Remarks	Conversion (%)	Yield of 2a (%)
1	SiO2	60 Å, 70–230 mesh	79	64
2	SIRAL 1	Al2O3/SiO2 99 : 1, 280 m^2/g	81	65
3	Aerosil 300	SiO2, 300 m^2/g	87	51
4	SiZr30	SiO2/ZrO2 = 30, 573 m^2/g	85	62
5	Zeolite beta, H^+ form	ZEO cat PBH, SiO2/Al2O3 25–60, 600 m^2/g	83	57
6	Ti-SBA15	SiO2/TiO2 = 30, 668 m^2/g	78	61
7	SBA 15	SiO2, 850 m^2/g	82	62
8	TiO2	Hombikat UV 100 (anatase), 250 m^2/g	81	50
9	Zeolite Y, H^+ form	CBV 720 (Zeolyst), SiO2/Al2O3 = 30, 780 m^2/g,	86	55
10	ZrO2	Monoclinic phase, (Alfa Aesar), 90 m^2/g	81	66
11	CeO2	Nanopowder (Aldrich), particle size ≤ 25 nm	82	70
12	Dowex Marathon A	Cl^− form (Aldrich), 1.3 meq/mL,	76	70
13	Montmorillonite K-10	Powder, (Aldrich), 250 m^2/g	84	58
14	None		60	40

Reaction conditions: limonene 0.4 g, NBS 1.3 equiv., catalyst 0.04 g, 5 mL acetone/H₂O 4 : 1 (v/v), r.t., 15 min. Conversion and yield were calculated by GC analysis using dodecane as the internal standard.