HBF₄/SiO₂-Catalyzed Ring Opening of Epoxides

Significance

HBF₄/SiO₂ catalyzed the ring-opening reactions of styrene oxide with N-heterocycles under mild reaction conditions. Thus, the reaction of indoles 1 with styrene oxide was carried out in the presence of 2 mol% of HBF₄/SiO₂ to give the 2-(3-indolyl)-2-phenylethanols 2 in 50-80% yield (eq. 1). Similarly, pyrroles 3 were converted into the corresponding adducts 4 in 50-75% yield along with 15% yield of the isomeric adducts 4′ (eq. 2). The reactions of imidazoles 5 with styrene oxide gave the corresponding adducts 6 in 63-70% yield (eq. 3).