2-Bromocyclohexanone Perhydrate—X-ray Crystal Structure and Conformational Effects on Reactivity in Sulfoxidations

The remarkably stable crystalline perhydrate 1 derived from α-bromocyclohexanone has been characterised by X-ray crystallography providing the first example of a perhydrate crystal structure. Perhydrate 1 exists in alternative chair conformations in chloroform and tetrahydrofuran with the bromine substituent occupying equatorial and axial positions, respectively. The perhydrate 1 can oxidise sulfides to sulfoxides in good yields in dichloromethane but not in tetrahydrofuran. The requirement for bromine to be equatorial for a stable perhydrate to form is demonstrated using conformationally locked cis and trans 2-bromo-4-tert-butylcyclohexanones in which case only the cis isomer 4a forms a perhydrate.