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Abstract Herein, we report for the first time the use of the nitrogen‐based bidentate molecule [2.2]pyridinophane (N2) as a ligand for metal complexes. Additionally, its improved synthesis allows for electronic modification of the pyridine rings to access the newpara‐dimethylamino‐[2.2]pyridinophane ligand (p‐NMe2N2). These ligands bind nickel in an analogous fashion to other pyridinophane ligands, completing the series of tetra‐, tri‐, and bidentate pyridinophane‐nickel complexes. The new compounds exhibit geometrically enforced C−H anagostic interactions between the ethylene bridge protons and the nickel center that are not present in other pyridinophane systems. These ethylene bridge groups also act as an unusual form of steric encumbrance, enforcing square planar geometries in ligand fields that would otherwise adopt tetrahedral structures. In addition, these anagostic interactions inhibit the catalytic performance in Csp3–Csp3Kumada cross coupling reactions relative to other common bidentate N‐ligand platforms, possibly by preventing the formation of the 5‐coordinate oxidative addition intermediates.
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Ligand‐Controlled Regiodivergence for Catalytic Stereoselective Semireduction of Allenamides
Abstract Ligand‐controlled regiodivergence has been developed for catalytic semireduction of allenamides with excellent chemo‐ and stereocontrol. This system also provides an example of catalytic regiodivergent semireduction of allenes for the first time. The divergence of the semireduction is enabled by ligand switch with the same palladium pre‐catalyst under operationally simple and mild conditions. Monodentate ligand XPhos exclusively promotes selective 1,2‐semireduction to afford allylic amides, while bidentate ligand BINAP completely switched the regioselectivity to 2,3‐semireduction, producing (E)‐enamide derivatives.
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- Award ID(s):
- 1945425
- PAR ID:
- 10303970
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 28
- Issue:
- 1
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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