Homogeneous Catalytic Hydroesterification of Complex Alkenes - Built-in Base Ligands Pave the Way for Disruptive Technology

The hydroesterification of highly demanding alkenes and industrially relevant bulk olefins (e.g. diisobuten) to corresponding esters has been studied. Herein a rationally designed Pd-catalyst based on a novel highly active class of ligands (built-in base) is used. Alkoxycarbonylation of a wide variety of alkenes in excellent yield is described. Initial steps towards the scale-up from laboratory to mini-plant-scale and validation of the process concept will be presented.

Results

The carbonylation of olefins is one of the most important homogeneously catalyzed reaction in industry. Within this group hydroesterification, also called Reppe reaction, represents a very promising and environment- friendly one pot method for obtaining carboxylic esters. Regularly, esters are produced by esterification of carboxylic acids with alcohols. In general, producing these carboxylic acids require multi-step processes, e.g. subsequent oxidation of alcohols or aldehydes obtained by hydroformylation.

In respect of green-chemistry, Pd-catalyzed hydroesterification of olefins has been studied quite extensively in the past several decades. However, the conversion of complex substrates like diisobuten to carboxylic esters is still challenging. Commonly used ligands, e.g. DTBPMB lead for complex olefins to significant lower yield and amounts of the unwanted byproduct ether. Fortunately, novel highly active ligands have been introduced for unprecedented conversion of complex olefins. ^[1,2] To obtain a framework of operation conditions, within constant product quality is guaranteed, Design of Experiments is used. Comparison of different separation technologies to recycle this unique homogeneous catalyst, lead to a sustainable process concept which is validated in a continuous operating mini-plant.^[3]

[1] K. Dong, X. Fang, S. Gülak, R. Franke, A. Spannenberg, H. Neumann, R. Jackstell, M. Beller, Nat. Commun. 2017, 8,14117.

[2] R. Sang, P. Kucmierczyk, K. Dong, R. Franke, H. Neumann, R. Jackstell, M. Beller, J. Am. Chem. Soc. 2018, 140, 5217-5223

[3] P. Kucmierczyk, R. Sang, D. Fridag, M. Beller, R. Franke, manuscript in preparation