Tetrahedron report number 724CH/π hydrogen bonds in organic reactions

The origin of the stereoselectivity of organic reactions such as Diels-Alder reactions, topochemical photoreactions, diastereoface- and enantioface-discriminating reactions and enantioselective catalytic reactions with transition metal complexes has been explored in the context of the CH/π hydrogen bond. The ground-state conformation of the reacting molecules, where CH/π hydrogen bonds play the central role, has been suggested to be the most important factor in controlling the stereoselectivity of the reactions. The underlying concept of the Cram and the Prelog rule was critically examined and a hypothesis has been presented that the π-facial selectivity is understood in terms of the conformational preference of the substrates. The contribution from the CH/π and CH/O hydrogen bonds has been suggested to be indispensable.Download full-size image