In the first chapter of this thesis, the development of two new reactions for the synthesis of vinyl ketenimines and alpha-oxo-ketenimines from isocyanides is presented. These palladium-catalyzed transformations both feature an isocyanide insertion / beta-hydride elimination sequence. Vinyl ketenimines were generated from allyl carbonates and were then hydrolyzed to beta,gamma-unsaturated carboxamides or converted to 1,5-disubstituted tetrazoles by treatment with hydrazoic acid. alpha-Oxo-ketenimines were efficiently prepared from alpha-halocarbonyl compounds with broad functional group tolerance and their reactivity profile was investigated. This led to the development of a one-pot three-component synthesis of pharmaceutically relevant tetrasubstituted 5-aminopyrazoles and to the synthesis of beta-ketoamidines in high yields. In the second chapter, synthetic studies towards the total synthesis of the alkaloid Mersilongine are presented. An advanced intermediate containing the quinolinic / bridged aminal core of this natural product was synthesized from vanillin in 20 steps. Three key transformations were successfully exploited or developed in this synthetic sequence : 1) A high yielding Tsuji-Trost reaction to create two adjacent tertiary carbon centers with high diastereoselectivity, 2) a substrate-controlled fully diastereoselective alpha-allylation of a lactone to form a quaternary center, 3) the first application of the iORC sequence for the synthesis of a quinolinic scaffold having three contiguous chiral centers. (iORC = integrated Oxidation / Reduction / Cyclization)