Water → 1,4-Dioxa-10,13-dithia-7,16-diazacyclooctadecane

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Reaction Steps

A solution of 7 g. of the cyclic diamide obtained in Example 28 in 100 ml. anhydrous tetrahydrofurane is added slowly to 50 ml. of a freshly prepared solution (1.5 M) of diborane in anhydrous tetrahydrofuran under nitrogen atmosphere and at a temperature of 0°C. The mixture is then heated to reflux for two hours. The excess reagent is destroyed by adding 10 ml. of water and the solution is evaporated to dryness on a rotatary evaporator under vacuum. 100 ml. 6N hydrochloric acid are added to the residue and the mixture is refluxed for two hours; a clear solution is obtained. This solution is then evaporated to dryness under vacuum. The residue is dissolved in 30 ml. water and the solution is pressed through a column of an anion exchange resin (Dowex 1, Trade Mark). The column is washed with water until there is no basic reaction. The combined water solutions obtained are evaporated to dryness under vacuum on a water bath (80°C - 100°C). The residue is recrystallized.

Provenance & Evidence