Development of Highly Stereoselective Reactions Using Lone Pairs of Oxygen Atoms

Abstract

Highly stereoselective reactions have been developed using lone pairs of oxygen atoms, in other words, the nucleophilic ability of oxygen atoms. They consist ofˆve types of reactions: 1) asymmetric synthesis using acetals, 2) organic reactions via Beckmann fragmentation intermediates, 3) organic reactions via dication equivalents, 4) rearrangement of 2,3-epoxy-1-alcohol derivatives, and 5) organic reactions using orthoesters. In this review, asymmetric syntheses using acetals are described in detail. They are divided into four categories: 1) diastereoselective 1,2-addition(alkylation, reduction) to the a-keto acetals and their derivatives, 2) asymmetric carbon-carbon bond formation by a combination of Beckmann fragmentation and asymmetric synthesis using C 2 -symmetric chiral acetals, 3) asymmetric synthesis via chiral oxonium ions prepared by intramolecular haloetheriˆcation of chiral ene acetals having C 2 -symmetric hydrobenzoin, and 4) asymmetric desymmetrization of meso-1,2-, meso-1,3-, and meso-1,4-diols via chiral oxonium ions prepared by intramolecular haloetheriˆcation of chiral ene acetals derived from optically pure norbornen aldehyde derivatives, and their applications to asymmetric syntheses of biologically active natural products.

Development of New Innovative Synthetic Organic Chemistry Using Lone Pairs of Oxygen Atoms

“…Since then, various types of asymmetric syntheses in this category have been developed. 45,46) All asymmetric reactions using chiral C 2 -symmetric acetals had been categorized to routes a and b before we developed the reactions classified to route c. The reactions in route c can form at least two chiral centers in remote positions. As far as I know, all reactions developed are new asymmetric reactions using C 2 -symmetric acetals.…”