Rhodium-catalyzed Cycloadditions and Cycloisomerizations Involving Propargylic Esters and Alcohols

Download or read book Rhodium-catalyzed Cycloadditions and Cycloisomerizations Involving Propargylic Esters and Alcohols written by Xiaoxun Li and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal-catalyzed cyloaddition and cycloisomerization reactions occupy a central position within the realm of organic synthesis. Research described in this thesis focuses on using propargylic esters and alcohols as building blocks for rhodium(I)-catalyzed cycloadditions and cycloisomerizations. The discovery and application of combining the [pi]-acidity and redox/insertion reactivity of rhodium(I) complexes, led to the development of many new reactions. By taking advantage of Rh-catalyzed 1,3-acyloxy migration of propargylic esters, I developed two tandem reactions. One is Rh-catalyzed carbonylation of 3-acyloxy-1,4-enynes (ACEs) for the synthesis of highly substituted cyclopentenones, and the other is ring expansion of cyclopropanes or cyclobutanes for the preparation of highly functionalized seven-membered or eight-membered carbocycles. By taking advantage of Rh-catalyzed 1,2-acyloxy migration of propargylic esters adjacent to heterocycles, I developed a novel and practical method for the preparation of a series of heterocycles including indoles, benzofurans, carbazoles and benzothiophenes from substituted pyrroles, furans, indoles and thiophenes. Inspired by the first Rh-catalyzed intra- and intermolecular [5+2] cycloadditions of 3-acyloxy-1,4-enynes (ACEs) with alkynes, I developed a new five-carbon building block, an inverted ACE, for [5+2] cycloadditions by switching the position of the alkene and alkyne groups in ACE. By replacing the acyloxy group in ACE with OH leaving group and aniline nucleophile, a completely new type of 5-carbon building block (HYE) was designed for cycloadditions. The tandem indole annulation and [5+1] cycloaddition was realized for the synthesis of various highly substituted carbazoles. Natural products glycosinine and mahanimbine were prepared. Furthermore, indolyl Rh(I)-carbene could be generated from 3-hydroxy-1,4-enyne (HYE) through a dehydration process. With different N-protecting group, I prepared dimeric indoles, cyclopropyl indoles, vinyl indoles and other interesting indole derivatives.