Phospholes benzophospholes

Phosphol-1-oxide, z.B. 1,2,5-Triphenyl- bzw. 7,2,3,4,5-Pentaphenyl-phosphol-1-oxid oder das in situ herstellbare 2-Phenyl-2H-2-benzophosphol-2-oxid, konnen als reaktive Diene mit geeigneten Dienophilen eine [4 + 2]-Cycloaddition eingehen. Beispielsweise... 

To the best of our knowledge, five-coordinate phospholes have not been investigated in the last decade. Only a series of five-coordinate benzophospholes 77 (Scheme 21, Section 3.15.5.2.1) has been described and characterized by NMR spectroscopy <2004RJC189>. 

Ylides derived from benzophospholes have attracted interest as participants in the Wittig reaction, where they give exceptionally high ratios of E- to Z-alkenes (90 10 or better) <87TL3445,93JOCl985>. They are also of interest in giving rather stable oxaphosphetane intermediates (191) in this reaction (Equation (40)) these five-coordinate phosphole derivatives are discussed in Section 2.15.7.3. 

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