2.3 General Principles of Diastereoselective Reactions: Diastereoselectivity via Substrate-Directable Reactions (Internal Delivery) and Heterocyclizations

摘要: Diastereoselective additions to unsaturated carbons may be induced by precomplexation of the reagent polar groups in substrate hydrogen bridging and metal complexes (internal delivery). These are syn steering group attack more hindered face sp 2 carbon. The phenomenon occurs acyclic cyclic systems alike (substrate-directable reactions) is extremely valuable view predictability stereochemical course magnitude induction. For instance, means substrate-directable reactions, olefinic double bonds epoxidized, cyclopropanated, hydrogenated, hydroformylated, or undergo cycloadditions, whereas carbonyl reduced internal delivery hydrogen. Similarly, reagents add units reversibly, reaction terminated intramolecular intervention a nucleophile (heterocyclization). This process effects heterocyclic ring closure under an additional functional (e.g., halolactonization, etc.).