A straightforward preparation of primary alkyl triflates and their utility in the synthesis of derivatives of ethidium

Abstract

The reaction of primary alcohols with trifluoromethanesulfonic anhydride in the presence of poly(4-vinylpyridine) [or poly(2,6-di-tert-butyl-4-vinylpyridine)] allows the isolation of the corresponding alkyl triflates in good yields. The quaternisation of 3,8-bis(ethoxycarbonylamino)-6-phenylphenanthridine (1) using these alkyl triflates was found to proceed smoothly at room temperature in nitrobenzene or chlorobenzene. Deprotection of these quaternary compounds using concentrated hydrobromic acid was found to be a more useful procedure than the previously reported use of concentrated sulfuric acid. The synthesis of the novel ethidium derivative 3,8-diamino-5-(5-aminopentyl)-6-phenylphenanthridinium bromide (12) is reported.