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In chapter one, the new application of (diacetoxyiodo)benzene(DIB) as a typical representative of hypervalent iodion regents in organic synthesis has been reviewed in detail. DIB has been widely applied in organic reactions, and obtaining many good results.In chapter two, the bromolactonization of alkenoic acids has been discussed. Lactonizations have been studied extensively, and this type of transformation serves as an important key reaction in a variety of syntheses. Usually, alkenoic acids are used to construct bromolactones with molecular bromine. However, bromolactonization has the restriction of molecular bromine is a toxic, difficult to handle, low-boiling lachrymatory liquid. Organic hypervalent iodine reagents have been received much attention due to their low toxicity, mild reactivity, ready availability, high stability and easy handing. They have found broad application in organic chemistry as alternatives replacing the highly toxic Hg(II), Tl(III) and Pb(IV) heavy-metal oxidants. Using hypervalent iodine reagents, the cyclization of alkenoic acids was investigated and found that the reaction was suitable for a series of 4-pentenoic acids, most of which gave good to excellent yields.In the first part of chapter two, it was found that the reaction of alkenoic acids with one equivalent of DIB and two equivalents of lithium bromide was easily be carried out in methanol at room temperature, got the bromolactones in good yields, in which the biggest yield can reach 95%. Then, the bromolactonization of alkenoic acids under catalytic hypervalent iodion regent was investigated. It was found when DIB was used as catalyst and Oxone○R ( KHSO4·2KHSO5·K2SO4)was used as co-oxidant, the reaction of alkenoic acids with sodium bromide was also fluent in CF3CH2OH at room temperature, obtaining good yields of bromolactones. In the last part, the new improvement for the bromolactonization of alkenoic acids is reported: the bromolactonization of alkenoic acid using catalytic KI or I2 to replace catalytic hypervalent iodion regent is also effect, giving good yield of bromolactone.In conclusion, the methods for bromolactonization of alkenoic acids have the advantages such as mild reaction conditions, simple procedure and“green”. Furthermore, the scope of use of hypervalent iodine reagents in organic synthesis have be extended.
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