Epoxides nucleophilic

Epoxides, like cyclic halonium ions, undergo ring opening through rearside attack of nucleophiles (see Section 6.3.2). Two mechanisms are shown, for both basic and acidic conditions. Under acidic conditions, protonation of the epoxide oxygen occurs first. The epoxidation-nucleophilic attack sequence also adds substituents to the double bond in an anti sense. 

Me o-epoxides, nucleophilic ring-opening reactions by aryllithium/(—)-sparteine (11) have been realized by Alexakis and coworkers with very good differentiation between the enantiotopic positions . Eliminative desymmetrization reactions of me o-oxacycles such as 144 or 147, which are triggered by an enantiotopos-differentiating deprotonation... 

Chiral A-amidino-l,2,3,4-tetrahydropyridines undergo a stereoselective epoxidation-nucleophilic opening sequence with either alcohols or organozinc reagents to give 2,3,6-trisubstituted piperidines where the relationship between the 2- and 3-positions is cis (Equation 15) <2005OL2747>. 

Scheme 5.2 Domino epoxidation-nucleophilic ring opening...

C4C im][BF4] Re03Me UHP Domino epoxidation-nucleophilic ring opening of glycols with dibutylphosphate product [17]... 

With unsymmetrical epoxides, nucleophilic attack occurs at the more substituted carbon atom. 

The reaction follows the same two-step process as the opening of epoxide rings with other negatively charged nucleophiles— that is, nucleophilic attack from the back side of the epoxide ring, followed by protonation of the resulting alkoxide. In unsymmetrical epoxides, nucleophilic attack occurs at the less substituted carbon atom. 

DOMINO MTO-CATALYZED EPOXIDATION-NUCLEOPHILIC RING OPENING OF GLYCALS... 

G. Soldaini, F. Cardona, A. Goti, Methyltrioxorhenium ctalyzed domino epoxidation-nucleophilic ring opening of glycals. Tetrahedron Lett. 44, 5589-5592 (2003). 

Normal range of nucleophilic reactivity, ease of preparation, thermal stability Efficient opening of epoxides Nucleophilic substitution and conjugate addition... 

For substituted epoxides, nucleophilic attack generally takes place at the less sterically hindered side of the epoxide. Using this type of reaction, show how you might prepare the following compound from benzene, ammonia, and any other reagents of your choice. 

Entry Epoxide Nucleophile Ratio of regioselectivity Conditions Attack at Attack at the more the less hindered hindered carbon carbon Yield (%)... 

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