Phosphonate stabilized anions derived from a variety of cyclic beta-ke
to phosphonates were shown to react with dimethyl acetylenedicarboxyla
te to afford [n + 2] ring expansion products. Highly substituted mediu
m sized rings containing phosphonate functionality were thus obtained
in reasonable yields. The reaction was found to proceed via a tandem M
ichael-aldol-fragmentation mechanism to give the ring enlarged product
s. An alternate competing pathway involving an ''abnormal Michael'' re
action was also shown to exist, resulting in a net 1,3-phosphorus migr
ation, without ring expansion. Furthermore, the electronic and steric
character of the carbonyl moiety of the cyclic beta-keto phosphonates
were shown to be very crucial in determining the course of the reactio
n.