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A simple two-phase, room temperature Schotten-Baumann procedure provides O-sulfobenzoylleucomethylene blue in good yield.
English (United States)
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Improved Synthesis of O-Sulfobenzoylleu-comethylene Blue
A simple two-phase, room temperature Schotten-Baumann procedure
provides O-sulfobenzoylleucomethylene blue in good yield.
Procedure: A two-phase system of EtOAc/H(2)O containing methylene blue
is reduced with sodium dithionite, adjusted to pH 5-6 with 40% NaOH, treated
with an EtOAc solution of O-sulfobenzoic anhydride (SBA) while maintaining the
pH at 4-6. The reaction occurs very quickly and is worked up by passing air
through the reaction mixture for several hours to consume excess
leucomethylene blue, then filtering, washing and drying to give the solid sodium
salt of O-sulfobenzoylleucomethylene blue. Yield crude approximately 90%.
Purification is effected by dissolving the crude material in hot methanol, adding
charcoal/CELITE* filtering, diluting with water (approximately 1:1), and cooling.
Filtration and drying afford the pure compound. * Trademark of Johns-Manville