Palladium-Catalyzed Amination of 2-Iodo-<i>para</i>-carborane

Abstract

The palladium-catalyzed Buchwald−Hartwig amination of B-iodocarborane by various azoles and amines is described for the first time. The reactions of 2-iodo-p-carborane with indole, imidazole, benzimidazole, or carbazole in the system Pd(dba)2−BINAP−ButONa in dioxane at 100 °C gave 2-p-carboranyl derivatives of these azoles in high yields together with 2-hydroxy-p-carborane as a side product. The reactions of 2-iodo-p-carborane with aromatic amines in the same system gave the amination products in 60−70% yields and also were accompanied by the formation of hydroxy derivatives (up to 30% yields). In a special investigation it was shown that the base ButONa was responsible for its formation. The principle possibility of the amination of 2-iodo-p-carborane by morpholine (with 30% yield) as an example of aliphatic amination was shown. The structures of N-(1,12-dicarba-closo-dodecaboran-2-yl)carbazole (1), N-(1,12-dicarba-closo-dodecaboran-2-yl)benzimidazole (2), N-(1,12-dicarba-closo-dodecaboran-2-yl)indole (4), and 2-hydroxy-1,12-dicarba-closo-dodecaborane (5) have been established by X-ray diffraction studies.