DERIVATIVES OF KETIPIC ACID .2. KETIPIC A CID DILACTONE AND RELATED-COMPOUNDS

The highly reactive title compound 7 was prepared by thermal decomposi tion of the disguised oxalylbisketene 6. Ring opening of 7 with nucleo philes leads to gamma-alkylidenetetronic acids 4. alpha-Substituted de rivatives of 4a give rise to unsymmetrical dilactones 9a-c and the dib romodilactone 9d. The alkylidenetronic acids are stabilized in the E c onfiguration by hydrogen bridges. the pairs of isomeric (E)- and (Z)-a lkylidenetetronic acids 3 and 4 show characteristic spectral differenc es.