Activation Of Rare Earth Metals And Its Application In Carbonyl And Sulfonyl Reduction

This dissertation mainly focuses on reactions of carbonyl compounds with rare earth metals induced by TiCl4 or I2, which can be divided into three parts.Firstly, we explored the reaction about the reduced deprotection of aryl esters which was reduced by Yb/I2. We found it can highly deprotect aryl esters with 2 equivalents Yb and 0.2 equivalents iodine. Next, aryl amides were conducted under the same condition. It is noteworthy that the reaction only adapted for the tertiary amides, and the secondary amides can be tolerated in this condition. Moreover, the aryl esters and amides can be reduced smoothly in the presence of cyano, acetal, chlorine atom, as well as conjugated double bonds, which indicates the reaction has well functional groups toleration. Finally, we find a method of deprotection of aryl esters and amides in a mild condition and convenient handled. Compared to the single electron reducing SmI2, it takes full use of rare earth metal with multiple electrons.Secondly, tosesters were tested with the Yb/I2 reducing system, which gave good yields, as we expected. In order to continue to examine the generality and scope of this reaction, tosamides were also conducted under the optimal condition. To our delight, we found that secondary tosamides were also gave excellent yields as well as tertiary ones. Thiocresol was produced meanwhile. Similar to the reaction of aryl esters and amides, this reducing system had excellent fountional toleration and selection. When the secondary aryl amide group and tosamide group were being in the same condition and only tosamide was reduced. Moreover, cyano, acetal, chlorine atom, as well as conjugated double bonds were also tolerated under this condition. Finally, to investigate the selectivity of this cleavage reaction, 2-(4-methylphenylsulfono) phenyl 4-methylbenzenesulfonate was tested in this condition. To our delight, we found when we used 3 equiv Yb and 0.6 equiv iodine, it gave the product with deprotection of tosester, but the completely deprotected product was given when the amount of the reducing agent was doubled. From this we can see that the tosester group was firstly reduced in the normal condition. The reducing system of SmI2 needes 6 equivalents SmI2, while our system only needs 3 equivalents metal, which indicate that our system takes full use of metal and is economical.Finally, we investigated the reducing coupling reaction of ketones and aldehydes induced by TiCl4/Yb. In the first place, we optimized the reaction condition, and ketones and aldehydes with different substitutes were tested under the optimal condition, which all gave the corresponding olefins in excellent yields. In the second place, with the aim of widening the scope of this transformation, we checked the ability of titanocene (IV) to promoted intermolecular cross-coupling reaction between dissimilar ketones. To our delight, the corresponding cross coupling products were given in excellent yields. In addition, the present reagent also performs the intermolecular coupling of diimines under milder conditions. The advantages of the present reductive system are the highest level of functional group and environmental tolerance, simple manipulation, least amount of metal-based reagents, and high chemoselectivity.