Diphosphorus tetraiodide iodination

Both yellow and red phosphorus ignite on contact with fluorine and chlorine red ignites in liquid bromine or in a heptane solution of chlorine at 0°C. Yellow phosphorus explodes in liquid bromine or chlorine, and ignites in contact with bromine vapour or solid iodine [1]. Interaction of bromine and white phosphorus in carbon disulfide gives a slimy by-product which explodes violently on heating [2], Interaction of phosphorus and iodine in carbon disulfide is rather rapid [3], A less hazardous preparation of diphosphorus tetraiodide from phosphorus trichloride and potassium iodide in ether is recommended [4],... 

Thus heating red phosphorus and lower alkyl iodides (ratio 1.5 3) in the presence of a trace of iodine or diphosphorus tetraiodide in an autoclave at 200 °C for eight hours, followed by treatment with aqueous sodium sulfite or successive treatments with nitric acid and aqueous base gave Me3PO (54%), Et3P0 (56%) and BU3PO (66%)... 

More important is the alkylation of red phosphorus in the presence of catalytic amounts of iodine or diphosphorus tetraiodide, which after hydrolytic working up leads to trialkylphosphine oxides, sometimes in high yield. Lower alkyl iodides are treated at 200-220° in a sealed tube or an autoclave,184 higher-boiling iodides at atmospheric pressure.185,186... 

New reagents for the primary and secondary alcohol to alkyl iodide conversion, with inversion at secondary centres, are diphosphorus tetraiodide (P2I4), a well characterized and stable solid, and mixtures of triphenylphosphine with iodine and imidazole or with 2,4,5-tri-iodoimidazole. The P2I4 system also iodinates tertiary alcohols. Trimethylsilyl iodide is known to convert alcohols into iodides (2,128), and some more systems that are believed to generate trimethylsilyl iodide in situ have been found to effect the alcohol to iodide conversion (c/. 3,151). Trimethylsilyl chloride-sodium iodide in acetonitrile produces iodides from alcohols direct or from their trimethylsilyl ethers. Hexamethyldisilane-... 

Related Reagents. Diphosphorus Tetraiodide lodotrimethyl-silane Triphenylhosphine-Iodine. 

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