Iron Catalysis in Organic Synthesis

Transition metal-catalyzed direct functionalization of C–H bonds is one of the key emerging strategies that is currently attracting tremendous attention with the aim to provide alternative environmentally friendly and efficient ways for the construction of C–C and C–hetero bonds. In particular, the strategy involving regioselective C–H activation assisted by various functional groups shows high potential, and significant achievements have been made in both the development of novel reactions and the mechanistic study. In this review, we attempt to give an overview of the development of utilizing the functionalities as directing groups. The discussion is directed towards the use of different functional groups as directing groups for the construction of C–C and C–hetero bonds via C–H activation using various transition metal catalysts. The synthetic applications and mechanistic features of these transformations will be discussed, and the review is organized on the basis of the type of directing groups and the type of bond being formed or the catalyst.

Transition metal-catalyzed C–H bond functionalizations by the use of diverse directing groups

The use of directing groups has proven to be a successful strategy to enhance reactivity and control selectivity in C–H functionalization reactions. In the past decade, a multitude of new transformations and new directing groups have been explored, and several recent reviews have discussed directing group approaches for C–H functionalization. This review focuses specifically on the use of monodentate nitrogen-based directing groups published during the past two years, with the aim of covering a body of literature that is complementary to existing reviews.

Recent advances in directed C–H functionalizations using monodentate nitrogen-based directing groups

Kunbing Ouyang,†,‡ Wei Hao,† Wen-Xiong Zhang,*,†,§ and Zhenfeng Xi† †Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China ‡Institute of Chemistry, Chinese Academy of Sciences (CAS), Beijing 100190, China State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China

Transition-Metal-Catalyzed Cleavage of C-N Single Bonds.

A combined experimental/computational study on the amino acid ligand-assisted Pd-catalyzed C–H bond activation reveals a mechanism in which the amino acid acts as both a dianionic bidentate ligand and a proton acceptor. This new model explains the effects of amino acids on reactivity and selectivity and unveils the dual roles of amino acids: stabilizing monomeric Pd complexes and serving as the internal base for proton abstraction.

https://web.pkusz.edu.cn/wu/files/2013/11/194.Role-of-N‑Acyl-Amino-Acid-Ligands-in-PdII-Catalyzed-Remote-C−H-Activation-of-Tethered-Arenes.pdf

Role of N-Acyl Amino Acid Ligands in Pd(II)-Catalyzed Remote C–H Activation of Tethered Arenes

Pd-catalyzed C-H lactonization for expedient synthesis of biaryl lactones and total synthesis of cannabinol.

https://www.rsc.org/suppdata/cc/c1/c1cc12790j/c1cc12790j.pdf

Catalytic decarboxylative alkylation of β-keto acids with sulfonamides via the cleavage of carbon-nitrogen and carbon-carbon bonds.

A Highly Diastereoselective Decarboxylative Mannich Reaction of β-Keto Acids with Optically Active N-Sulfinyl α-Imino Esters

A range of protected γ-oxo-α-amino esters have been prepared in a highly regio- and stereoselective manner through the decarboxylative Mannich reaction of β-keto acids with optically active N-tert-butanesulfinyl α-imino esters in the presence of 3 mol % La(OTf)3 or 5 mol % Y(OTf)3 at 20 °C. Preliminary mechanistic studies indicate that the reaction proceeds through imine addition followed by decarboxylation.

A Highly Diastereoselective Decarboxylative Mannich Reaction of β‐Keto Acids with Optically Active N‐Sulfinyl α‐Imino Esters.

A range of β-keto acids smoothly undergo decarboxylative alkylations with N-benzylic or N-allylic sulfonamides in the presence of FeCl3 to afford structurally diverse unsymmetric ketones in good to excellent yields and with extremely high regioselectivity.

Jian-Yong Wang

Papers

Pd-catalyzed C-H lactonization for expedient synthesis of biaryl lactones and total synthesis of cannabinol.

Catalytic decarboxylative alkylation of β-keto acids with sulfonamides via the cleavage of carbon-nitrogen and carbon-carbon bonds.

A Highly Diastereoselective Decarboxylative Mannich Reaction of β-Keto Acids with Optically Active N-Sulfinyl α-Imino Esters

A Highly Diastereoselective Decarboxylative Mannich Reaction of β‐Keto Acids with Optically Active N‐Sulfinyl α‐Imino Esters.

Catalytic Decarboxylative Alkylation of β‐Keto Acids with Sulfonamides via the Cleavage of Carbon—Nitrogen and Carbon—Carbon Bonds.