diastereoselektiota

Diastereoselektiota refers to a type of stereoselective chemical reaction where the reaction produces one or more than one diastereomer in greater proportion than the other possible diastereomers. In a chemical reaction that creates new stereocenters, if the starting materials are achiral but the products are chiral, and if the reaction produces a mixture of stereoisomers, diastereoselektiota describes the situation where a specific set of stereoisomers (diastereomers) is preferentially formed. This is distinct from enantioselektiota, which is the preferential formation of one enantiomer over another.

Diastereoselective reactions are common in organic chemistry and are crucial for synthesizing complex molecules with specific three-dimensional structures. For example, in many addition reactions to alkenes or carbonyl compounds that already possess a stereocenter, the newly formed stereocenter can be influenced by the existing one, leading to a preference for certain diastereomers. The degree of selectivity can be measured by the diastereomeric ratio (dr), which is the ratio of the amounts of the different diastereomers formed.

Factors influencing diastereoselektiota include steric hindrance, electronic effects, and the presence of directing groups. Transition state models, such as the Felkin-Anh model or the Cram chelation model, are often used to predict and explain the observed diastereoselectivity in specific reactions. Understanding and controlling diastereoselektiota is essential for designing efficient synthetic routes in fields like pharmaceuticals and materials science, where precise control over molecular architecture is paramount.