The Methyl Enol Ethers of Ethyl 2, 4-Dioxopentanoate

Methylation of ethyl 2, 4-dioxopentanoate with diazomethane gives a mixture of two enol ethers, the 2-methoxy and the 4-methoxy isomer, with a product ratio which depends upon reaction temperature. Both enol ethers, initially (Z)-configurated, isomerize to the corresponding (E)-conformers, the 4-methoxy compound with particular ease.