Hypervalent Iodine(III)Compounds in Organic Synthesis

点击翻译按钮获取中文摘要

In'this project, we have studied on the developement of novel reactions using hypervalent iodine(III)compounds and the application to the synthesis of biologically active natural products.i)We recently developed the novel direct azidation of p-substituted phenol ethers using phenyliodine(III)bis(trifluoroacetate)(PIFA)in polar and low nucleophilic solvents such as CF_3CH_2OH and(CF_3)_2CHOH.We found that the reaction proceeds via cation radical intermediates by UV and ESR spectroscopic studies. The reaction is effective for introductions of oxygen, carbon, and sulfur nucleophiles. We could apply the reaction to the intramolecular oxidative phenolic coupling. On the other hand, in CH_3CN the alkyl azidation occurrs at the benzylic position of p-substituted phenol cthers.ii)Although the reagents having azido or cyano ligands are known to be quite useful for the azidation of various compounds or for other reactions, they are too labile to be isolated. The cyclic iodinanes having azido, cyano, and nitrooxy ligands, which are crystalline and air-stable could be prepared.iii)We recently reported the total synthesis of marine antitumor alkaloid, discorhabdin C by PIFA induced cyclization of p-substituted phenolic aminoquinones. It was found that the cyclization of phenol derivatives bearing aminoquinones at the omicron-or m-position provides a versatile route to spirodienones and lH-azepines. Furthermore, the novel synthetic method for N,S-acetal, which is the essential structure of discorhabdin alkaloids, by the cleavage of the beta-lactam ring was also developed.