Triphenylphosphine Oxide Catalyzed Dihalogenation Of Unsaturated Compounds

In this thesis, the systematic research on triphenylphosphine oxide catalyzed dihalogenation of unsaturated compound is described. This thesis involves the following four chapters.Chapter 1:In this chapter, the previous researches on the dihalogenation reactions and applications of phosphine oxide in organic synthesis were introduced. Some dihalogenated organic compounds are key intermediates in the synthese of natural products and some pharmaceuticals, meanwhile, they are also very useful synthons in organic synthesis. Therefore, development of novel dihalogenation reaction has great significance for both scientific study and practical production. Phosphine oxides are often used as catalyst or additive in organic chemical transformations. Recent years, some creactive transformations using phosphine oxides were reported, which will further broaden the application of these compounds.Chapter 2:In this chapter, firstly, the recent researches on the 1,3-dichlorination reactions and applications of triphenylphosphine oxide were described. Based on these researches, we successfully developed an unusual PPh3O catalyzed stereoselective 1,3-dichlorination of unsaturated ketoester with oxalyl chloride as the chlorine source. The products were produced with moderate to good yields and excellent stereoselectivities. Moreover, this method was also proved to be suitable for gram-scale synthesis. Considering the relatively few examples of 1,3-dichlorination reactions, this work nicely complements the current research in dichlorination field. The novel activation model in this reaction can be applied to other reaction and the application of PPh3O is extended as well.Chapter 3:Based on our previous work, we successfully developed a PPh3O catalyzed stereoselective poly- and dibromination of unsaturated compounds with oxalyl bromide as the bromine source. The brominated products were obtained with good to excellent yields and excellent diastereoselectivities. It should be noted that the dibromination of β,γ-unsaturated a-ketoesters has not been reported before. The byproducts are gas, which makes the purification much easy. This reaction not only efficiently complements the field of bromination, but also provides a potential route to the synthesis of chiral dibrominated compounds. Moreover, it discovers a practical usage of PPh3O, which is considered as waste in many reactions.Chapter 4:Firstly, a strategy called "Waste as catalyst or additive", which could greatly improve the atom economy of the reaction, was described. Inspired by this strategy, we developed an atom economical one-pot method for the syntheses of di- and poly- brominated esters from simple aldehydes. Brominated esters were obtained with moderate to good yields and excellent diastereoselectivities. Triphenylphosphine oxide, which is produced as byproduct in Wittig reaction, directly serves as the catalyst for the next bromination step. Therefore, it makes great improvement in atom economy and operation simplicity and needs less time. Considering that PPh3O is also produced as byproduct in many other reactions, we think this strategy will have a broad application.