Synthesis and X-ray structures of new concave π-prismand hydrocarbon [2.2.1]m,p,p- and [2.2.1]p,p,p-cyclophanes

Abstract

The synthesis of the smaller analogues of the well-known [2.2.2]p,p,p-cyclophane (1) π-prismand were performed ia a well-established pyrolysis route from the corresponding disulfones. In spite of their smaller size and increased rigidity, these cyclophanes showed remarkably similar complexation behaviour with Ag⁺ ions compared to [2.2.2]p,p,p-cyclophane. X-Ray crystal structure determinations showed the bis-sulfide 12 (1,10-dithia[3.3.1]m,p,p-cyclophane) to be helically chiral. The single crystal X-ray analysis showed that the reduction of the ring size from 17-membered hydrocarbon 17 to 16-membered hydrocarbon 16 has only a slight effect on the size and shape of the cavity. In the Ag⁺ complex of [2.2.1]m,p,p-cyclophane (18) the interaction between silver and hydrocarbon is accomplished by the coordination of silver to one double bond in two phenyl rings and to only one carbon of the third phenyl ring. However, in the case of [2.2.1]p,p,p-cyclophane–Ag⁺ triflate (19), silver is bonded to one of the double bonds in each phenyl ring. Similarly to larger [2.2.2]cyclophanes the conformations of the parent [2.2.1]m,p,p- (16) and [2.2.1]p,p,p-cyclophanes (17) do not change dramatically upon the complexation with the Ag⁺ ion.