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Nucleophilic Substitution at Phosphorus Centres - Old and Recent Studies and a Final Solution of Mechanistic and
1Department of Organic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363, Łódź, POLAND.
Abstract:
Among many problems of a fundamental value in the heteroatom chemistry the mechanism and stereochemistry of the nucleophilic substitution reaction at the phosphorus and other heteroatom centres have attracted great attention of phosphorus chemists already in the middle of the last century. This review, which does not have a comprehensive character, summarizes the selected original contributions aimed at solution of the mechanism of SN2-P reaction and its relationship with stereochemistry. The breakthrough in these studies was the Westheimer's concept and his rules which is presented at the beginning of this article. Next, a series of papers is presented where the stereochemistry of the substitution at phosphorus was investigated in cyclic five-, four- and six-membered ring phosphorus compound. The majority of these reactions have been found to occur with retention of the P-configuration. In the third part of this account, the selected examples of substitution reactions at phosphorus in acyclic compounds are discussed. As the results of all the investigations discussed did not allow to undoubtedly ascribe the mechanism (SN2 or A-E) to the investigated reactions, in the last part the SN-P reactions are presented, the mechanism of which has been established by combination of the stereochemical and DFT-studies.
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