Building the “Phosphoindigo” Backbone by Oxidative Coupling of Phosphindolin‐3‐ones with Selenium Dioxide |
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Authors: | Sebastian Vollbrecht,Guergana Dobreva,Ioana Cartis,Wolf‐W. du Mont,Jö rg Jeske,Frank Ruthe,Peter G. Jones,Ludger Ernst,Walter Grahn,Ulrich Papke,Michael Marzini,Hermann A. Mayer |
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Abstract: | Oxidative coupling of racemic 1‐ethoxy‐1‐oxophosphindolin‐3‐one ( 1 ) and its 5‐CF3‐derivative 6 with SeO2 furnishes 1,1′‐diphosphaindigo derivatives 5 and 7 as bis‐phosphinic esters, i. e. as PV‐compounds. Like indigo and thioindigo, 5 and 7 exist in the E‐configuration; the crude products of 5 and 7 are mixtures of isomers that are trans‐ and cis‐configurated with respect to the relative orientation of the ester groups oat phosphorus. The structure of the centrosymmetric E‐P(R)P′(S) isomer [(E)‐trans‐isomer] of 5 was determined by X‐ray crystallography. Ester cleavage of 5 , followed by addition of triethylamine to bis‐phosphinic acid 9 (the 1,1,1′,1′‐tetroxide of “phosphoindigo”), furnishes the related bis‐triethylammonium salt 10 as a crystalline hydrate that exhibits an extended hydrogen bonding network. |
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Keywords: | Indigo dyes Phosphindole Phosphinic acids Oxidative coupling |
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