The regioselective ring opening of epoxides using elemental iodine and bromine in the presence of o-phenylenediamine as a new catalyst affords vicinal iodo alcohols and bromo alcohols in high yields. The major advantages of this method are versatility, high regioselectivity, a cheap and commercially available catalyst, mild and neutral reaction conditions, and short reaction times. Fourier transform Raman spectroscopy was used to study the reaction of iodine with o-phenylenediamine. The results indicate that the complex [(Diamine)I]þ  I5  is formed, and we suggest that the major nucleophile is the pentaiodide ion. This bulky nucleophile has a fundamental role in the high regioselectivity observed attacking the less sterically hindered epoxide carbon.

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