Studies On The Coupling Cyclization Of SmI₂ Mediated β- Heteroatom Ketones To Synthesis Of Cyclic Alcohol

SmI₂ is an excellent reductive coupling reagent in organic synthesis, The dissertation investigated the reductive cyclization reactions of (3-heteroatom substituted ketones mediated by SmI2. The dissertation consists of three parts:The first part briefly introduces the advances of samarium diiodide promoted reductive coupling reactions, especially in the reductive coupling reactions between unsaturated compounds and carbonyl groups including "-alkenyl-carbonyl " "alkynyl carbonyl" "aryl-carbonyl" reductive coupling reactions.The second part of the study investigated the SmI₂ mediated reductive cyclization reactions of (3-aryIthio ketones, which provides a way to get access to dihydro-thiochroman alcohol compounds. The reaction conditions are mild and high diastereoselectivity and good yields were achieved. The reaction mechanism was also proposed and the "aryl-carbonyl" coupling occurred in the process instead of reductive removal of the arylthio group. The high diastereoselectivity was attributed to the chair-form conformation of the 6-membered ring of the transition state.Part three focused on the samarium diiodide mediated reductive cyclization of P-benzotriazolyl ketones. For P-aryl （or alkyl） β-benzotriazolyl ketones, reductive removal of the benzotriazolyl afforded the corresponding carbonion, and subsequent intramolecular ring-closure afforded cyclopentanols in satisfactory yields. Interstingly, for the β-alkenyl β-benzotriazolyl ketones, the C -Bt bond cleavage was further accompanied byfree radical migration, and the two processes led to the generation of cyclopent-3-enols with good yields and high diastereoselectivity.