Iron-Catalyzed α-Methylation of Ketones Using Methanol as the C1 Source under Photoirradiation.

A mild, environmentally benign approach for α-methylation of ketones utilizing methanol as the C1 source under visible light has been developed. The reaction conditions were favorable for a wide range of ketones with both aromatic and aliphatic backbones, allowing for good-to-excellent yields of the respective products. The tentative mechanism is postulated after preliminary mechanistic and kinetic experiments.

α-Alkylation of Ketones with Secondary Alcohols Catalyzed by Well-Defined Cp*CoIII -Complexes.

Although α-alkylation of ketones with primary alcohols by transition-metal catalysis is well-known, the same process with secondary alcohols is arduous and complicated by self-condensation. Herein a well-defined, high-valence cobalt(III)-catalyst was applied for successful α-alkylation of ketones with secondary alcohols. A wide-variety of secondary alcohols, which include cyclic, acyclic, symmetrical, and unsymmetrical compounds, was employed as alkylating agents to produce ß-alkyl aryl ketones.

Cobalt-Catalyzed Reductive Alkylation of Amines with Carboxylic Acids.

Direct reductive alkylation of amines with carboxylic acid is carried out by using an inexpensive, air-stable cobalt/triphos catalytic system with molecular hydrogen as the reductant. This efficient synthetic method proceeds through reduction and condensation, followed by reduction of the in situ-generated imine into the amine in a green catalytic process.

Cp*CoIII -Catalyzed Efficient Dehydrogenation of Secondary Alcohols.

A novel, well-defined molecular Cp*CoIII complex was isolated and structurally characterized for the first time. The efficiency of this cobalt catalyst was demonstrated in the alcohol dehydrogenation and dehydrative coupling of secondary alcohols under mild conditions into ketones and ethers, respectively.

Cp*Co(III)-Catalyzed C-H Alkylation with Maleimides Using Weakly Coordinating Carbonyl Directing Groups.

A novel protocol for ortho-C-H alkylation of aromatic and heteroaromatic ketones and esters under Cp*Co(III) catalysis has been developed for the first time. The reaction proceeds through initial cyclometalation via weak chelation-assisted C-H bond activation, followed by coordination of activated alkene, insertion between Co-C, and protodemetalation.

Isolation of Cp*CoIII -Alkenyl Intermediate in Efficient Cobalt-Catalyzed C-H Alkenylation with Alkynes.

A general and efficient procedure for C-H alkenylation of arenes with a broad substrate scope catalyzed by Cp*CoIII was demonstrated with alkynes. A highly selective mono-alkenylation and sequential bis-C-H bond functionalization was displayed to exemplify the versatility of the cobalt catalyst. Isolation of cationic Cp*CoIII -alkenyl intermediate was achieved under identical catalytic conditions to further establish the proposed pathway.

Iron-Catalyzed Sustainable Synthesis of Pyrrole.

Efficient, sustainable, highly regiospecific substituted pyrroles were synthesized using a well-defined, air stable, molecular iron(0) complex. The developed methodology is broadly applicable and tolerates a variety of functional groups. C-2, C-3, and C-2 & C-4 substituted pyrroles were synthesized in good yield. Symmetrical bis-pyrroles were accessible for the first time using an iron catalyst. On the basis of the experimental observation, we propose that the reaction proceeds through a hydrogen autotransfer process followed by second oxidation/intramolecular dehydrative condensation to provide the pyrrole.

Iron-Catalyzed Allylic Amination Directly from Allylic Alcohols.

Allylic amination, directly from alcohols, has been demonstrated without any Lewis acid activators using an efficient and regiospecific molecular iron catalyst. Various amines and alcohols were employed and the reaction proceeded through the oxidation/reduction (redox) pathway. A direct one-step synthesis of common drugs, such as cinnarizine and nafetifine, was exhibited from cinnamyl alcohol that produced water as side product.