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DOI: 10.1055/s-1994-25691
Organophosphorus Compounds; 96.1 Cyclotetramerization of Phosphaalkynes to 1,3,5,7-Tetraphosphacubanes
Publication History
Publication Date:
25 April 2002 (online)
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Depending on the reaction conditions, small amounts of the tetraphosphapentacyclic compounds (tetraphosphacubanes)4a, b as well as the isomeric tetraphosphatetracyclic products 5a, b can be isolated from the thermolyses of the phosphaalkynes 3a, b. This cyclotetramerization can be directed towards the formation of tetraphosphacubanes when the whole process is split into two sequential cyclodimerizations. Firstly, the zirconocene-phosphaalkyne dimer complexes 8a-d are prepared from 7 and 3a-d; in the second step, the CP2Zr fragment is extruded from 8a-d by reaction with hexachloroethane. The tetraphosphacubanes 4a-d are obtained in good yields by this process. Only in the case of 1-adamantylphosphaacetylene are the penta- and tetracyclic products formed concomitantly (7 + 3e → 8e → 11 + 12). Putative intermediates for the second dimerization step are the diphosphetes 9a-e and their Diels-Alder dimers 10a-e.