Synthesis of the ethyl oxalyl tetracarbonyl iron anion [(CO)4FeCOCO2Et]–, its methylation at the metal into (CO)4Fe(Me)(COCO2Et) and further carbon–carbon coupling into ethyl pyruvate

Abstract

The stable anion [(CO)₄FeCOCO₂Et]^–(2)[obtained after reaction of EtOCOCOCl on Na₂Fe(CO)₄] is methylated at the metal by reaction with MeSO₃CF₃ at –50 °C to give (CO)₄Fe(Me)(COCO₂Et)(3) characterized in situ by ¹H and ¹³C NMR; at –30 °C it decomposes according to two pathways: reductive elimination into MeCOCO₂Et (4) and Fe₃(CO)₁₂ and rearrangement into (CO)₄Fe(COMe)(CO₂Et)(5) which decarbonylates at +5 °C before giving MeCO₂Et (6) and Fe(CO)₅.