Mechanistic investigations and ligand development for rhodium catalyzed [2+2+2] and zinc catalyzed [4+2] cycloadditions
Date
2013
Authors
Dalton, Derek M., author
Rovis, Tomislav, advisor
Wood, John L., committee member
Kennan, Alan J., committee member
Rappé, Anthony K., committee member
Snow, Christopher D., committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Described herein are mechanistic studies and ligand development for Rh(I) catalyzed [2+2+2] cycloaddition reactions of alkene tethered isocyanates and exogenous alkynes. A mechanistic hypothesis has been proposed and supported through experiment. Novel perfluoroaryl Taddol phosphoramidite ligands were developed based on the mechanistic hypothesis. Improvements in product and enantioselectivity were found using the perfluoroaryl Taddol phosphoramidite ligand, CKphos. This catalyst system was studied by NMR, X-ray and DFT calculations. Rh(I)-C6F5 and Co(-1)-C6F5 interactions were found in the course of studying the CKphos catalysts. The Rh-CKphos catalyst system was used in the synthesis of the tricyclic core structure of the cylindricine and lepadiformine alkaloids. Finally a Zn(II)-catalyzed [4+2] cycloaddition of 1- azabutadienes and nitro olefins was discovered and developed as an efficient and selective means to synthesize tetrahydropyridines.
Description
Rights Access
Subject
cycloaddition
zinc
rhodium
enantioselective
heterocycles
catalysis