Synthesis of (E)-4-oxo-5-hexenals and their acetal derivatives

Article abstract of DOI:10.1055/s-1990-27125

An effective synthesis of (E)-4-oxo-5-hexenals 6 and the acetals 5 starting from ethyl 2-alkoxy-1-cyclopropanecarboxylates 1a-d is presented. The acid-induced ring opening of the cyclopropanecarboxylates 1a, b followed by phosphorylmethylation or the phosphorylmethylation of the ester 1c followed by ring opening leads to the 5-acetal of 2,5-dioxopentylphosphonate 4. The Horner-Emmons olefination of 4 with various aldehydes produces the title compounds.