Selective Preparation of Diamondoid Phosphonates

We present an effective sequence for the preparation of phosphonic acid derivatives of the diamondoids diamantane, triamantane, [121]­tetramantane, and [1­(2,3)­4]­pentamantane. The reactions of the corresponding diamondoid hydroxy derivatives with PCl<sub>3</sub> in sulfuric or trifluoroacetic acid give mono- as well as didichlorophosphorylated diamondoids in high preparative yields.