Cyclic phosphorus compounds, reaction pathway

In conclusion, we may expect further advances in understanding factors controlling structural and conformational preferences of cyclic oxyphosphoranes, both from an experimental as well as a theoretical point of view. As the area continues to develop, the use of oxyphosphoranes as models in mechanistic interpretation should enhance our understanding of pathways followed in nucleophilic displacement reactions of tetracoordinated phosphorus compounds. Acknowledgment... 

In principle, the reaction between a dihaloalkane (9) and a phosphorus(III) ester (10 (R = alkyl, aryl or alkoxy) initially affords the haloalkyl compound 11 the use of a trialkyl phosphite would thus lead to an (co-haloalkyl)phosphonic diester 11 (R = alkoxy, R = alkyl), whilst that of a phosphonite diester (10 R = alkyl, aryl) would afford an (co-haloalkyl)alkyl(or aryl)phosphinic ester. Depending on the ratio of reactants, further reaction might then take place (pathway A), resulting in the formation of the compounds 12. Depending also on n, and on the reaction temperature, the alternative pathway B may be followed the products are then cyclic phosphonic or phosphinic acid derivatives 13, and examples following both reaction pathways have been discussed (chapter 2, Section A). 

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