Stereoelectronic control, the principle

Stereoelectronic control, the principle of least nuclear motion and the theory of, 24,113... 

Stability and reactivity of crown-ether complexes, 17, 279 Stereochemistry, static and dynamic, of alkyl and analogous groups, 25, 1 Stereoelectronic control, the principle of least nuclear motion and the theory of, 24, 113 Stereoselection in elementary steps of organic reactions, 6, 185 Steric isotope effects, experiments on the nature of, 10, 1... 

Stereochemistry, static and dynamic, of alkyl and analogous groups, 25, 1 Stereoelectronic control, the principle of... 

As a consequence of the principle of stereoelectronic control, the reverse process, i. e. the addition of an alcohol to an oxonium ion (e.g. 117 113) must take place through a precise pathway. Evidence on this pathway comes from the X-ray analysis (80, 81) of molecules containing an amino group and a carbonyl group in close proximity (e.g. 119) (see also (82)). 

The authors have rationalized their results on the basis of the principle of stereoelectronic control. The reaction of methoxide ion on 227 gives the intermediate 228 which can eject chloride ion to give the Z isomer 229. The... 

Nuclear motion, the principle of least, and the theory of stereoelectronic control, 24, 113 Nucleophiles, partitioning of carbocations between addition and deprotonation. 35, 67 Nucleophilic aromatic photosubstitution, 11,225 Nucleophilic catalysis of ester hydrolysis and related reactions, 5,237 Nucleophilic displacement reactions, gas-phase, 21, 197... 

Nuclear motion, the principle of least, and the theory of stereoelectronic control,... 

Application of the principle of stereoelectronic control to the hydrolysis of esters under basic conditions leads to the following predictions Z esters are allowed to undergo carbonyl-oxygen exchange but E esters cannot. 

An interesting experimental result was observed in the study of the mild acid hydrolysis of the cis and the trans bicyclic orthoesters 87 and 88 (60). The cis orthoester 87 gave under kinetically controlled conditions the dihydroxy methyl ester 89 whereas the trans orthoester 88 produced directly the hydroxy-lactone 90 under the same experimental conditions. These results can be explained on the basis of the principle of stereoelectronic control. 

Further experimental evidence supporting the principle of stereoelectronic control in the cleavage of hemi-orthoamide tetrahedral intermediates has been obtained from studies on the carbonyl-oxygen exchange during the basic hydrolysis of amides, and from the hydrolysis of imidate salts. These experiments are described next. 

We will see that this technique can be used to demonstrate the importance of the principle of stereoelectronic control in tetrahedral intermediates derived from amides. Primary, secondary, and tertiary amides as well as N — H and N-alkyllactams will be examined. 

The fact that there is carbonyl-oxygen exchange in primary and secondary amides is in accord with the principle of stereoelectronic control but it does not constitute a proof since these experimental results can be explained without the use of this principle. 

These results confirm that under acidic or neutral conditions, the hydrolysis of imidate salts yield only the ester and amine products via the T+ and T4 ionic form. They also show that under basic conditions some imidate salts (56 and 57) yield only the ester and amine product whereas others (54 and 55) give a mixture of ester and amine plus amide and alcohol products. This difference in behavior of imidate salts can be readily explained by taking into account the principle of stereoelectronic control and by assuming that imidate salts 56 and 57 exist in the anti conformation whereas imidate salts 54 and 55 exist either in the syn conformation or as a mixture of the syn and anti conformations. 

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