2-Phosphonocyclopenten-2-ones from ε-tert-butyldimethylsilyloxy-α-diazo-β-ketophosphonates via a rhodium(II)-catalysed C–H insertion reaction

The exposure of certain primary ε-tert-butyldimethylsilyloxy-α-diazo-β-ketophosphonates to the action of catalytic rhodium(II) in refluxing toluene leads to a C–H insertion followed by elimination of the silyloxy group to give 2-phosphonocyclopenten-2-ones in fairly good yields.