Michael addition of N-acylaminomalonates to propynoic esters led to th
e (E)-4-(N-acylamino)-4-carboxy-2-pentenedioic triesters IIa - IIf. On
deprotection and decarboxylation, these compounds afforded 2-(N-acyl-
amino)-2-pentenedioic acid derivatives IIIa - IIIc. Dimethyl (E)-4-dia
zo-2-pentenedioate (IV) was prepared by direct transfer of the diazo g
roup. On treatment of IV with 4-toluenesulfonic acid, 2-(4-toluene-sul
fonyloxy)-2-pentenedioate (V) was formed. Iodination of (E)-2-pentened
ioic acid led directly to the 2,4-diiodo derivative VII. From dimethyl
(E)-4-oxo-2-pentenedioate the oximino ester VIIIa and the free oximin
o acid VIIIb were prepared.