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

Table 3

Solvent effect on the bromohydroxylation of 1a.

Entry	Solvent	Conversion (%)	Yield of 2a (%)
1	Acetone	76	70
2	Acetone^a	89	82
3	MeOH	88	79^b
4	DMSO	84	63
5	THF	80	63
6	Nitromethane	75	26
7	Acetonitrile	72	49
8	Dichloroethane	55	23

Reaction conditions: 1a 0.4 g, NBS 1.3 equiv., catalyst (Dowex Marathon A, Cl⁻ form) 0.04 g, 5 mL solvent/H₂O 4 : 1 (v/v), r.t., 15 min; ^aat 0°C; ^bformation of 2-bromo-1-methoxy-1-methyl-4-(1-methylethenyl)-cyclohexane. Conversion and yield were calculated by GC using dodecane as the internal standard.