Preparation and crystal structure of a twin twist-boat bicyclo[3.3.1]nonane monohydrate

Abstract

Reduction of 3,3,7,7-tetramethyl-2,6-dimethylenebicyclo[3.3.1]nonane bis(epoxide)(7) with lithium aluminium hydride affords a mixture of exo-2,exo-6-dihydroxy-2,3,3,6,7,7- hexamethylbicyclo[3.3.1]nonane (8) and exo-2-hydroxy,exo-6-hydroxymethyl-2,3,3,7,7- pentamethylbicyclo[3.3.1]nonane (9). The diol (8) was obtained as its monohydrate, the crystal structure of which [Pa= 7.388(2), b= 9.292(2), c= 11.466(2)Å; α= 80.52(2), β= 89.68(1), γ= 70.85(2)°; Z= 2] was determined with a final R= 0.049. In the solid state the bicyclo[3.3.1]nonane skeleton of (8) exists in a flattened twin twist-boat conformation and four neighbouring diols are linked by a fully hydrogen-bonded water molecule. The co-crystallisation behaviour shown by (8) is quite different from the helical tubuland arrangement exhibited by other alicyclic diols closely related in structure, but is fully in accord with that of a previously recognised family of alcohol hemihydrates based on the pentamethylethanol structure.