Ligand-Controlled Palladium-Catalyzed Decarboxylative Heck Coupling for Regioselective Access to Branched Olefins

Abstract

A highly chemo-and regioselective decarboxylative Heck-type coupling of carboxylic acids and terminal olefins has been developed using a catalytic system composed of Pd(OAc) 2 in the presence of phosphine-sulfonamido ligands. Using the bulky ligand L1 leads to high selectivity for 1,1-disubstituted (branched; b) olefins that are generally difficult to obtain. The influence of all relevant reaction parameters was evaluated using a combination of design of experiments and one factor at a time optimization. The coupling of dimethoxy-benzoic acid with various olefinic substrates gave the corresponding branched olefins with excellent regioselectivity (b/l up to 42:1) in up to 80% isolated yields. In contrast, using the less bulky ligand L2 results in the inverse regioselectivity leading to the 1,2-disubstituted (linear; l) product again in high yield of 86% (b/l = 1:26). Detailed investigation of the mechanistic pathways by DFT calculations reveals that the sterically demanding aryl substituent at the sulfonamide group of ligand L1 favors the pathway via 1,2-insertion with an energy preference of 4.4 kcal/mol, thus furnishing the 1,1-disubstituted branched olefins. In contrast, the 2,1-insertion reaction is advantageous by 1.3 kcal/mol for the analogous less bulky ligand L2 leading to the linear products.

Controlling Reactivity and Selectivity in the Mizoroki–Heck Reaction: High Throughput Evaluation of 1,5-Diaza-3,7-diphosphacyclooctane Ligands

“…DFT calculations uncovered a favorable π–π interaction between the styrene group and the P Ph 2 N ArCF3 2 ligand, which could explain its preference for the linear pathway. Conversely, the bulky P t Bu 2 N ArCF3 2 ligand destabilizes this pathway due to steric hindrance, inverting the regiochemical outcome . P 2 N 2 s are well-known to be powerful ligands, particularly due to the flexible, basic nitrogen atoms in the ligand’s second-coordination sphere, enabling H 2 splitting and related transformations .…”

Computational design of cooperatively acting molecular catalyst systems: carbene based tungsten- or molybdenum-catalysts with rhodium- or iridium-complexes for the ionic hydrogenation of N2 to NH3

“…The choice of B97D3-BJ functional stemmed from its computational efficiency and its consistency with our prior research on metal–ligand complexes, aligning well with experimental findings. 13,55,56 However, we also conducted a comparative study involving other DFT functionals for the critical intermediates (TDI) and transition states (TDTS), which are mentioned in detail in the ESI (Fig. S1†).…”

“…One must note, however, that it cannot be excluded completely, that unexpected side reactions may be accessible in an experimental system which might not have been envisioned or possibly overlooked in the prior computational work. Computational studies of this kind have demonstrated their potential to narrow down significantly the plethora of choices an experimentalist could make with the potential of predictive catalyst design for example for olefin hydrogenation, 16 decarboxylative Heck-type coupling 13 and direct insertion of CO 2 14,15 into arenes.…”

“…In this work we use computationally guided catalyst design for the identification of suitable catalyst systems which bases on DFT computations following an approach which has been used earlier by us and was successfully transferred to experimental chemistry. 13–16…”