Anomalous behaviour of Rh(II)-generated carbonyl ylides: entry into functionalized spiro dioxa-bridged polycyclic frameworks

A series of symmetrical α,β-unsaturated ketone systems having multiple π-bonds were synthesized. To generate five-membered-ring carbonyl ylides as intermediates, the rhodium(II)-catalyzed reactions of α-diazo ketones were carried out and the carbonyl ylides reacted with the π-bonded α,β-unsaturated ketone systems. Functionalized spiro dioxa-bridged polycyclic ring systems were produced with high regio- and chemoselectivity in good yields.