Ligand Field Sensitive Spin Acceleration in the Iron-Catalyzed [2 + 2] Cycloaddition of Unactivated Alkenes and Dienes.

Redox-active pyridine(diimine) (PDI) iron catalysts promote the reversible [2 + 2] cycloaddition of alkenes and dienes to cyclobutane derivatives that have applications ranging from fuels to chemically recyclable polymers. Metallacycles were identified as key intermediates, and spin crossover from the singlet to the triplet surface was calculated to facilitate the reductive coupling step responsible for the formation of the four-membered ring. In this work, a series of sterically and electronically differentiated PDI ligands was studied for the [2 + 2] cycloaddition of ethylene and butadiene to vinylcyclobutane.

-Symmetric Pyridine(diimine) Iron Methyl Complexes for Catalytic [2+2] Cycloaddition and Hydrovinylation: Metallacycle Geometry Determines Selectivity.

A series of -symmetric (aryl,alkyl)-substituted pyridine(dimine) iron methyl (APDI)FeCH complexes have been prepared, characterized, and evaluated as precatalysts for the [2+2]-cycloaddition of butadiene and ethylene. Mixtures of vinylcyclobutane and ()-hexa-1,4-diene were observed in each case. By comparison, -symmetric, arylated (PDI) iron catalysts are exclusively selective for reversible [2+2]-cycloaddition to yield vinylcyclobutane.

Enantioselective Cp Rh -Catalyzed Carboaminations of Acrylates.

Enantioselective carboaminations of olefins constitute an attractive strategy for a rapid increase in molecular complexity from readily available starting materials. Reported here is an intermolecular asymmetric carboamination of acrylates using rhodium(III)-catalyzed alkenyl C-H activations of N-enoxysuccinimides to generate the nitrogen and carbon portion for the transfer. A rhodium complex equipped with a tailored bulky trisubstituted chiral Cp ligand ensures carboamination chemoselectivity as well high levels of enantioinduction.

Chiral cyclopentadienyl Rh-catalyzed enantioselective cyclopropanation of electron-deficient olefins enable rapid access to UPF-648 and oxylipin natural products.

Chiral cyclopentadienyl Rh complexes efficiently catalyze enantioselective cyclopropanations of electron-deficient olefins with -enoxysuccinimides as the C1 unit. Excellent asymmetric inductions and high diastereoselectivities can be obtained for a wide range of substrate combinations. The reaction proceeds under mild conditions without precautions to exclude air and water.