During this PhD thesis, the reactivity of metal carbenes derived from acceptor-acceptor diazo reagents was studied, and subsequent ylide intermediates were then formed and used for different transformations. On one hand, the reactivity of acceptor-acceptor diazo reagents, diazomalonates in particular, was explored for N-H insertions with aliphatic and aromatic amines as Lewis bases under iridium catalysis. On the other hand, inspired by previous studies in the group, cyclic ethers on the way to oxonium ylides were further studied as nucleophiles. A new reactivity was developed under Rh(II) and Pd(II) catalysis with α-diazo-β-ketoester reagents this time. Additionally, a straightforward strategy to synthesize complicated molecules with multiple macrocycles is described in this thesis.