This thesis contains two research topics. The first topic is decarbonylative electrophilic addition of α-amino acids to give α-substituted amines. The in situ NMR monitoring experiments showed the formation of the key intermediates, iminiums, which allowed us to control the condition precisely. The iminium intermediates can further reaction with various carbon nucleophiles to undergo electrophilic aromatic substitution reaction, Grignard reaction, and Mannich reaction. The second chapter is applied intramolecular decarbonylative electrophilic aromatic substitution reaction to synthesis crispine A. The proton NMR spectra identify the iminium and aldehyde intermediates of intramolecular decarbonylative electrophilic aromatic substitution reaction.