Diboron → 1,4,10,13-Tetrathia-7,16-diazacyclooctadecane

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Reaction Steps

A solution of diborane (20 ml.; 1.5 N) in anhydrous tetrahydrofuran is added dropwise to a suspension of 2 g. of the diamide obtained in Example 32 in 50 ml. anhydrous tetrahydrofurane under nitrogen at room temperature. The solid dissolves giving a clear solution. After the addition is completed the mixture is refluxed during four hours and a solid precipitate is formed. After cooling to room temperature, the excess reagent is destroyed by adding carefully 10 ml. of water. The solvents are evaporated to dryness and 6 N hydrochloric acid (50 ml.) is added to the solid residue. The mixture is refluxed for three hours: the solid does not dissolve, the mixture remaining heterogeneous. The mixture is evaporated to dryness and a solution of 10% sodium hydroxide in water (50 ml.) is added to the residue.

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