Tandem ring expansion/aldol cyclization of bicyclo[5.4.01,7]undecanediones

Diazomethane ring expansion of 3 followed by deketalization, led to the formation of bicyclodione intermediates 6 and 8. These intermediates underwent internal aldol cyclization to give the tricyclic adducts 7 and 9 in a 1:1 ratio, respectively.