Syntheses and crystal structures of seven alicyclic diols which crystallise with layer structures instead of the helical tubuland inclusion lattice

Abstract

In an exploration of the possibility of modifying the shape and size of the helical canal host structure known to occur in crystals of several bi- and tri-cyclic diols, we report the syntheses and crystal structures of seven further diols: endo-2,endo-6-dihydroxy-2,6-dimethylbicyclo[3.3.1]nonane (5); endo-2,endo-6-dihydroxy-2,6-dimethyl-9-thiabicyclo[3.3.1]nonane (6); 2,6-dihydroxy-2,6-dimethyltricyclo[3.3.1.1^3,7]decane (7); anti-4,anti-8-dihydroxy-4,8-dimethyl-2-thiatricyclo[3.3.1.1^3,7]decane (8); syn-2,syn-7-dihydroxy-2,7-diethyltricyclo[4.3.1.1^3,8]undecane (9); anti-2,anti-7-dihydroxy-2,7-diethyltricyclo[4.3.1.1^3,8]undecane (10); and syn-2,anti-8-dihydroxy-2,8-dimethyl-tricyclo[5.3.1.1^3,9]dodecane (11). All seven of these adopt similar layered crystal structures. The properties characteristic of these structures are: two-dimensional hydrogen bonding of diol molecules within the layers, maximised hydrogen bonding for each diol, an absence of inter-layer hydrogen bonding, and the occurrence of cycles of four hydrogen bonds connecting four diol molecules within the layers. The closed cycles of hydrogen bonds are in contrast with the extended helical spines characteristic of the helical canal host lattice. The layered diol structures do not include guests and do not involve spontaneous resolution of the diol molecules.