The first examples of asymmetric epoxidation of dihydroquinoline substrates using iminium salt organocatalysts are reported. The 3,4-epoxytetrahydroquinoline products are obtained in good yields and with moderate to good enantioselectivities.

A number of stable new N-H oxaziridines have been designed and prepared, and their reactivity as electrophilic sources of nitrogen investigated. 3-tert-Butyl-3-phenyloxaziridine is the most efficient and stable and has potential for use as a general reagent for this purpose.

Enantiomerically enriched epoxides are useful intermediates that have found many applications in asymmetric synthesis, and development of efficient catalysts for asymmetric epoxidation has received considerable attention. In this manuscript we describe the design, preparation, and use of new highly selective iminium salt organocatalysts for asymmetric epoxidation, based around a chiral binaphthalene motif coupled with a chiral substituted dioxane moiety. The new catalysts have been tested in the catalytic asymmetric epoxidation of unfunctionalized alkenes, and provide up to 95 % ee. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

An organocatalytic asymmetric epoxidation reaction using iminium salt catalysts is described, in which the stoichiometric persulfate oxidant is generated electrochemically. This system offers comparable ees to the use of commercially available persulfate. Electrochemically generated percarbonate ion is also a successful and novel oxidant system for use with iminium salts.

Iminium salt organocatalysts can provide high selectivity and high efficiency in catalytic asymmetric epoxidation. They are normally used in conjunction with Oxone as the stoichiometric oxidant. Oxone, however, has limited stability and is insoluble in most organic solvents; we report here for the first time the development of a reaction system driven by hydrogen peroxide as the stoichiometric oxidant, involving an unusual double catalytic cycle.