Tetraethyl [[1,1'-biphenyl]-4,4'-diylbis(methylene)]bis(phosphonate) → HCID 72337841, compound

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Reaction Steps

0.93 g (8.1 mmol) of potassium tert-butoxide and then 2.70 g (7.16 mmol) of 10-mesityl-5,5-dioxophenothiazine-3-carbaldehyde (example 35b) were added at room temperature with stirring under nitrogen to a solution of 1.63 g (3.58 mmol) of diethyl[4′-(diethoxyphosphorylmethyl)biphenyl-4-ylmethyl]phosphonate (U.S. Pat. No. 3,984,399, example 2, column 29, lines 58-66) in 40 ml of dimethyl sulfoxide which has been dried over a molecular sieve. After stirring at room temperature for 4 h, the reaction solution was diluted with 200 ml of methanol and stirred for a further 1 h. The precipitate was filtered off, washed with 100 ml of methanol, stirred up again in 300 ml of methanol, filtered again and dried at 35° C. under reduced pressure. The crude product (2.90 g) was recrystallized twice from dimethylformamide and once from chlorobenzene. The crystals were filtered off with suction, washed successively with chlorobenzene and ethanol, filtered off with suction and dried at 80° C. under reduced pressure. After the removal of solvent residues under high vacuum (2×10−5 mbar) at 250° C., 0.98 g (30% of theory) of analytically pure luminous yellow microcrystals having an m.p. of >350° C. were obtained, whose solution in chloroform fluoresced at λ=456, 485 (S), 522 (S) nm.

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