Addition Reactions: Polar Addition

Engineered alkane dehydrohalogenases (HLDs) have been shown to effect transhalogenation. Pre-organization of geranyllinalool and its esters in a self-assembled cage has been shown to lead to a U-shaped foldamer, owing to a combination of hydrophobic and polar interactions between the substrate and the elements of the cage, as revealed by X-ray crystallography and nuclear magnetic resonance spectroscopy. Amplification of the electrophilicity of N-chlorosuccinimide by irradiation with visible light in the presence of an organic dye photocatalyst, in particular Methylene Green, has allowed chlorination of aromatics and heteroaromatics. High-level calculations have demonstrated poor correlation between the proton affinity, reactivity, and cation stability of a series of chlorinated ethenes and propenes towards HCl in the gas phase, possibly because of the concerted mechanism avoiding the formation of carbocations.