RING EXPANSION REACTIONS OF CYCLIC BETA-KETO PHOSPHONATES

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.