Optically active calixarenes conduced by methylene substitution.

The first method for the synthesis of optically active calix[4]arenes that are chiral as a result of substitution on the methylene bridges is described. The key step in the synthesis involves the reaction of a biscarbene complex with a diyne, which generates two of the benzene rings and the macrocyclic ring of the calix in a single transformation. The utility of this triple annulation process is demonstrated in the synthesis of di- and tetramethoxycalix[4]arenes. The flexibility of this synthetic approach is demonstrated by the synthesis of two diastereomers of the tetramethoxycalix[4]arenes in which each is synthesized in a stereoselective fashion by proper control of the absolute configurations of the methoxy groups in the biscarbene complex and in the diyne.