Silicon-phosphorus analogies rate controlling factors in SN2(P) reactions influence of the nucleophile for a given stereochemistry
✍ Scribed by Robert J.P. Corriu; Gérard F. Lanneau; Dominique Leclercq
- Publisher
- Elsevier Science
- Year
- 1983
- Tongue
- French
- Weight
- 213 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
SN2(P) reactions of chlorophosphates, which take place with inversion of configuration, are higly dependent upon the nature of the nucleophile. On the contrary, exocyclic substitutions of five-membered ring chlorophosphates with retention show a marked kinetic levelling effect. SN2(P) processes with displacement of the P-X bonds (X = halogen, OR, SR . ..) are commonly accepted as an extension of Westheimer's concepts. 1-4 The current mechanism involves initial formation of the most stable P(5) intermediate of trigonal bipyramidal (tbp) geometry, with apical entry of the nucleophile. If the leaving group is also in apical position, the reaction proceeds directly (inversion). If the better leaving group is in equatorial position, ligand reorganization (via pseudorotation or other) allows consecutive departure from an apical position (retention), 0 \ .0CH3 C H30,? 3 P HO' '0