Elucidation of Mechanism on the Heteroatom-Directed Stereoselection and its Application to Organic Synthesis.

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In order to elucidate the role of heteroatoms on the diastereoselection in the electrophilic addition reaction to allylically substituted olefins, the amino group of allylic amines is examined, because the electronic nature of the amino group is able to be controlled systematically by changing the substituents on the nitrogen atom both in terms of the lone pair electrons on the nitrogen atom and also in terms of the sigma electrons of the C-N bond.The sterically defined unsymmetrically substituted amines are, however, not available by the existing methods and two synthetic methods have been developed. The first is the palladium catalyzed transformation of 4-vinyl-1, 3-dioxane-2-ones into 4-vinyl-1-oxa-3-azacyclohexan-2-ones. The second is the silver catalyzed aminocyclization of N-tosyl O-(2, 3-butadienyl) carbamates to N-tosyl-4-vinyl-2-oxazolidinones. By these reactions unsymmetrically substituted allylic amines are prepared and used for an iodoetherification.Iodoetherification of N-substituted 3-amino-4-penten-1-ols provides a mixture of cis and trans-2-iodomethyl-3-aminotetrahydrofurans. The cis/trans selectivity in this cyclization is examined, changing the N-substituents (acetyl, benzoyl, p-nitrobenzoyl, trifluoroacetyl, p-toluenesulfonyl, methanesulfonyl, and trifluoromethanesulfonyl). The reactivity in the cyclization decreases in this order of substituents, while the selectivity (cis/trans) increases in this order. Based on these results, a precise mechanism of the HETEROATOM EFFECT is proposed.