Ethoxycarbonylation of 5-dethia-3-keto-4-methyl-5-oxacephams

Abstract

Due to their multifunctional character, the ethoxycarbonylation of 3-keto-5-oxa-cephams (10, 27 and 28) using ethyl cyanoformate in THF/HMPA solution led to expected products 14, 27 and 29 in a low yield only. Apart from the desired compounds, the O-acylation, C-alkylation at C-7, and the addition of CN¯ anion to the keto group were also observed.

A New Mild Method for the C-Acylation of Ketone Enolates. A Convenient Synthesis of β-Keto-Esters, -Thionoesters, and -Thioesters

“…These conditions afforded the desired β-keto ester enol 2 in 46% yield (Table , entry 2), alongside a multitude of other undesired byproducts. Presumably the latter arose from the starting ketone and the initially formed products, both reacting with the cyanide ion that was being liberated as the reaction progressed, an outcome that has previously been documented for certain ketones when enolate C-acylation is attempted with the Mander reagent and base.…”