ABSTRACT
Bifunctional phosphorus-based organocatalysts proved to be highly efficient for the atom-economic reaction of CO2 and epoxidized oleochemicals. Notably, those products are obtained from CO2 and renewable feedstocks only. Structure-activity relationships have been deduced from a screening of 22 organocatalysts in a test reaction. Bifunctional catalysts based on a phosphonium salt bearing a simple phenolic moiety proved to be extraordinarily active under comparatively mild and solvent-free reaction conditions. In the presence of the most active organocatalyst 12 oleochemical carbonates were isolated in excellent yields up to 99 %. This organocatalyzed reaction represents an excellent example for the realization of the 12 Principles of Green Chemistry as well as the 12 Principles of CO2 Chemistry.
Subject(s)
Carbon Dioxide/chemistry , Carbonates/chemistry , Fatty Acids/chemistry , Fatty Acids/chemical synthesis , Catalysis , Chemistry Techniques, Synthetic , Epoxy Compounds/chemistry , Green Chemistry TechnologyABSTRACT
An efficient and practical protocol for the enantioselective cobalt-catalyzed hydrovinylation of vinylarenes with ethylene at low (1.2â bar) pressure has been developed. As precatalysts, stable [L2 CoCl2 ] complexes are employed that are activated in situ with Et2 AlCl. A modular chiral TADDOL-derived phosphine-phosphite ligand was identified that allows the conversion of a broad spectrum of substrates, including heterocyclic vinylarenes and vinylferrocene, to smoothly afford the branched products with up to 99 % ee and virtually complete regioselectivity. Even polar functional groups, such as OH, NH2 , CN, and CO2 R, are tolerated.
ABSTRACT
The absolute control of the regiochemistry of a cobalt-catalyzed 1,4-hydrovinylation reaction is achieved by alternation of the ligands applied. While the dppe/dppp ligands led to the formation of the branched product, the herein described application of the SchmalzPhos ligand generates the corresponding linear product in both excellent yields and regioselectivities. The catalyst system exhibits a high tolerance toward functional groups, and the very mild reaction conditions allow the synthesis of 1,4-dienes without isomerization into conjugated systems.
