Synthesis and stereochemistry of some new brominated spiro 1,3-dioxanes

New dibrominated spiro 1,3-dioxanes have been obtained by a regio- and diastereo-selective reaction between six-membered ring spiro compounds and bromine. Studies on the stereochemistry of these brominated compounds, exhibiting a 1,5-dioxaspiro[5.5]undecane skeleton, were carried out by NMR methods in solution and by the solid-state molecular structure of four compounds established by single-crystal X-ray diffractometry. The diasteroselectivity of the bromination was explained by the asymmetric Induction of chiral carbon atoms and the chiral spiro skeleton.