3,7,9-TRIHETERABICYCLO[3.3.2]DECAN-10-ONES - AN UNUSUAL FAMILY OF HETEROCYCLES OBTAINED FROM 3,7-DIHETERABICYCLO[3.3.1]NONAN-9-ONES

A series of new 3,7,9-triheterabicyclo[3.3.2]decan-10-ones is reported for the first time. Members of the family of 3,7-diheterabicyclo[3.3. 1]nonan-9-ones served as precursors of the title compounds. Spectral e vidence suggests the 3,7,9-triheterabicyclo[3.3.2]decan-10-ones exist in a chair-boat (CB) reversible boat-chair (BC) equilibrium in solutio n. It is speculated that steric hindrance around the carbonyl group an d possibly the variance in conformation BC versus CC of the individual 3,7-diheterabicydo-[3.3.1]nonan-9-one precursors in solution may infl uence the ease of oxygen and nitrogen insertion in the ring enlargemen t to give the title molecules. Confirmation that three members of the bicyclo[3.3.2] decan-10-ones exist in BC forms in the solid state was achieved via single crystal X-ray diffraction analysis for -benzyl-3-t hia-7,9-diazabicyclo[3.3.2]decan-10-one (4a), 7-dibenzyl-3,7,9-triazab icyclo-[3.3.2]decan-10-one (4c), and dibenzyl-9-oxa-3,7-diazabicyclo[3 .3.2]decan-10-one (4d).