Oxidation and Reduction of Bis-Phosphonio-Isophosphindolides: from Phosphorus Crown Ethers to Phosphine-Functionalized Phospholides

Anellated Heterophospholes and Phospholides and Analogies with Related Non-Phosphorus Systems

“…The structures have been confirmed by X-ray crystal investigations . The reaction of lithium-1,3-bis(diphenylphosphino)isophosphindolide 58 with Ni(CO) 4 leads to coordination of the exocyclic phosphorus atoms. ,

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“…More representatives 55 (R = Ph, 2-pyridyl, X = Cl, Br, F 3 CSO 3 ) having other substituents at the phosphonio group and counteranions have been prepared in a similar manner . The neutral monophosphonio species 56 , 57 , and alkali benzophospholide 58 have been obtained from the reduction of 55 . − Alkali naphthalenide, magnesium, and NaBH 4 104 have been used as the reducing agents (Scheme ).

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“…Bis(phosphonio)isophosphindolides, which display a related but symmetric π-excessive aromatic system with charge compensation by substituents, lack this high sensitivity to water or alcohol . However, electron withdrawal from phosphorus by coordination to transition metal cations or by oxidation enhances the reactivity and promotes rapid reaction with H 2 O, alcohols, or H 2 S. 102c,,− In 1,3-benzazaphospholes and 1-phosphaindolizines, the +M effect of the nitrogen electron-pair reduces the polarity of the CP bond and makes these compounds more resistant to hydrolysis. Analogously, 1,3-benzoxaphospholes are stabilized by the +M effect of the O-atom.…”

“…The metal-assisted oxidative addition of alcohols to 55 can also be achieved in the presence of oxygen and catalytic amounts of Cu(I) 205b. Oxidative halogenation of 55 (R = Ph) by Cl 2 and Br 2 is accompanied by substitution of the benzene ring, whereas PhICl 2 affects selective P-dichlorination. ,

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“…102 The neutral monophosphonio species 56, 57, and alkali benzophospholide 58 have been obtained from the reduction of 55. [103][104][105] Alkali naphthalenide, 103 magnesium, 103 and NaBH 4 104 have been used as the reducing agents (Scheme 19).…”