The First Efficient Procedure For Hemialdals From Acetophenones

Hemialdal is a product formally formed by losing a H2O from two aldehyde hydrates. Hemialdal is not familiar with chemist because it has only been isolated as byproducts in very low yield or as unstable intermediate in organic synthesis.We have developed a new method to obtain this type of compound. A variety of acetophenones were readily oxidized by dimethyl sulfoxide with an iodine catalyst to afford the corresponding hemialdals in moderate yieids with high stereoselectivities. The synthesis is simple, convenient and practical. This represents the first efficient procedure for preparing hemialdals from acetophenones and makes it possible to carry out research into the chemistry of hemialdals—a completely new field.The most prominent features in the structures of hemialdals are the"W"conformation, which is stabilized by a combination of stereoelectronic effects and intramolecular hydrogen bonding. The structure was determined by X-ray crystallographic analysis.