Within this PhD thesis, the reactivity of metal carbenes derived from diazodiesters was tackled using cyclic ketones as primary substrates to afford selectively malonate enol ethers and oxygen-containing heterocycles in single step processes, depending on the choice of metal catalyst. In a first approach, with cyclopentadienyl-ruthenium(II) as catalyst and via carbonyl ylide intermediate, an effective and straightforward synthesis of malonate enol ethers was developed. A wide scope of products was obtained including enol ethers of different ring sizes, geometries and bearing various additional functional groups. The mechanism of the reaction was studied via deuterium labeling experiments and a mechanistic pathway was elucidated based on DFT calculations. In a second instance, it was demonstrated that cyclic ketones and diazodiesters react under Rh(II) catalysis, and with Rh₂(esp)₂ in particular, to obtain 1,4-dioxene adducts through a double carbene addition process. The key for the mono or double-addition selectivity is linked to the difference in intrinsic electrophilicity between the Ru or Rh-metal carbenes.

These enol ethers display a dual reactivity as they present two different nucleophilic sites, the enol and the malonate groups. This double reactivity was exploited, separately, to access a wide scope of functionalized malonate enol ethers. Furthermore, with selected branched precursors, two examples of annulation processes were developed to afford chromene derivatives under Lewis-acid mediated conditions.

The late-stage functionalization of enol ethers was expanded to visible-light promoted photoredox catalysis. In this approach, two different radical cyclizations were developed. First, with alkyl bromide enol ether, an oxaspiro[4.5]decane was obtained after a 5-exo-trig ring-closure. On the other hand, and of special interest for originality, unprecedented reactivity was observed with bromocarbonyl malonate enol ethers that afforded a trans-fused bicyclo[4.3.0]nonane. After extensive optimization studies, fused bicycles of this type with different ring sizes and functional groups were obtained even if the method presents quite a few limitations. The mechanism of cyclization was investigated in depth using photophysical and NMR methods and a proposal was elucidated based on the results.