This dissertation will focus on four main areas: The first aspect to be discussed will be reaction of allyl 2-diazo-2-phenylacetates with trimethylsilyl thioethers in the presence of rhodium(II) catalysts. These conditions generate α-allyl-α-thio silyl esters which undergo a spontaneous Ireland–Claisen rearrangement. Competing side-reactions, substrate scope and application will be explored. The second aspect to be discussed will be metal-catalyzed halogen insertion into α-diazocarbonyl compounds. Attempts to optimize the reaction and efforts to obtain asymmetric induction will be explored. The third aspect to be discussed will be rhodium(II)-catalyzed carbene transfer from trimethylsilyldiazomethane to arylmethyl thioethers, generating sulfonium ylides that undergo [2,3]-sigmatropic rearrangement, punching quaternary centers into aromatic rings. Substrate scope and competing side-reactions will be discussed. The final aspect to be discussed will be rhodium(II)-catalyzed carbene transfer from trimethylsilyldiazomethane to allylic thioesters, generating S-acyl allylsulfonium ylides that undergo [2,3]-sigmatropic rearrangement. This is the first report of an S-acyl Doyle-Kirmse reaction.