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Unusual Solvent-Promoted Smiles Rearrangement of Two Different Phosphorus-Containing Organolithium Compounds to the Same Lithium Phosphide. Crystal Structure of MeP{C6H4-2-CH(C6H4-2-CH2NMe2)NMe2}Li(THF)2

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journal contribution
posted on 18.01.2002, 00:00 by Keith Izod, Paul O'Shaughness, William Clegg
Treatment of the tertiary phosphines RP(C6H4-2-CH2NMe2)2 (R = Me, 1; R = i-Pr, 4) with n-BuLi in THF yields the lithium phosphides [RP{C6H4-2-CH(C6H4-2-CH2NMe2)NMe2}]Li(THF)2 (R = Me, 5; R = i-Pr, 6) as the sole phosphorus-containing products. Compound 5 is also obtained when either the lithium phosphinomethanide Li{CH2P(C6H4-2-CH2NMe2)2} (3) or the benzyllithium complex [MeP(C6H4-2-CH2NMe2){C6H4-2-CH(Li)NMe2}]2 (2) is dissolved in THF. Conversion of 2 to 5 is extremely rapid, whereas conversion of 3 to 5 takes several days at room temperature. The deuterium-labeled compound Li{CH2P(C6H4-2-CD2NMe2)2} (3a) isomerizes in THF to DCH2P(C6H4-2-CD(C6H4-2-CD2NMe2)NMe2}Li(THF)2 (5a) and shows a strong kinetic isotope effect in comparison to the isomerization of 3. Compounds 5 and 6 have been characterized by multinuclear NMR spectroscopy and X-ray crystallography, and a mechanism for their formation from 14 is proposed.