The Study Onallylation Promoted By Lewis Acid Mg(â…¡) And Applica Tion Into Drug Synthesis

This thesis aims at the study on the allylation of imines or in situ imines with allyltributylstannane promoted by Lewis acidic Mg(II). This dissertation consists of three parts as following:Chapter1reviewed the Lewis acid-catalyzed allylation of aldimines and its asymmetric allylation involved chiral amines and chiral catalysts.In chapter2, the allylation of aldimines promoted by MgI2etherate [MgI2·(OEt2)n] was investigated. Results and mechanistic discussions on the systematic studies of one-pot allylation of aldehyde, amine with allyltributylstannane are documented. The results suggest (1) MgI2·(OEt2)n is effective to a variety of aldehydes such as aromatic, heteroaromatic, aliphatic and α, β-unsaturated, which could smoothly afford the desired homoallylic amines in good to excellent yields.(2) MgI2·(OEt2)n-catalyzed allylation exhibits high chemoselectivity toward aldehydes in the presences of its parent aldimines. The crossover experiments suggests that aldehyde is firstly activated by MgI2·(OEt2)n and affords homoallylic alcohol. This magnesium-catalyzed allylation is mild, efficient and operationally simple. Iodide counterion, weakly coordinating peripheral ethereal ligands for Mg (II), and a non-coordinating reaction media are critical factors for the unique reactivity of this catalytic system.Asymmetric allylation of aldehydes with chiral auxiliary amines promoted by MgI2etherate was investigated in chapter three. L-phenylalaninol was proved to be the better chiral auxiliary amine according to its reactivity and stereoselectivity. The allylation of a variety of aldehydes with L-phenylalaninol was studied. The primary results show good yields and excellent diastereoselectivity. The reactivity and stereoselectivity of aldehydes are subjected to its electronic effect of substitution group on the aromatic ring. One of the investigated asymmetric allylation is applied into the synthesis of sitagliptin. This synthetic approach represents a new methodology for the synthesis of chiral β-amino acid derivatives.