Organic chemistry frontiers 

About: Organic chemistry frontiers is an academic journal published by Royal Society of Chemistry. The journal publishes majorly in the area(s): Chemistry & Catalysis. It has an ISSN identifier of 2052-4110. Over the lifetime, 4352 publications have been published receiving 67116 citations.

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

Abstract: 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.

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

Abstract: 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.

Nickel-catalyzed reductive coupling of alkyl halides with other electrophiles: concept and mechanistic considerations

Abstract: The formation of C–C bonds directly by catalytic reductive cross-coupling of two different electrophiles represents one of the practical synthetic protocols that differs from the conventional nucleophile/electrophile coupling methods. Particularly the reductive coupling of alkyl electrophiles with other electrophiles is still a challenge. This report summarizes the advances in the formation of C(sp3)–C(sp3) bonds between two alkyl electrophiles, with emphasis on the control of chemoselectivity that is exceedingly challenging to achieve due to similar structures and reactivities of two unactivated alkyl halides. The coupling of alkyl halides with aryl or acyl electrophiles was also discussed based on the chemical approach developed by our group, followed by a brief overview of the reactions of tertiary alkyl halides. In the end, a brief overview of the challenges in this exciting field was illustrated. Whereas the reaction mechanisms generating alkyl–alkyl products are proposed to involve reactions of Ni(I) species with alkyl halides to generate Ralkyl–Ni(III)–Ralkyl intermediates through a radical/Ni cage-rebound process, the obtained evidence seemingly supports that the radical chain mechanism governs the acylation and arylation of alkyl halides. The latter features a cage-escaped alkyl radical.

Chiral N,N′-dioxide ligands: synthesis, coordination chemistry and asymmetric catalysis

Abstract: A class of conformationally flexible ligands composed of a tertiary amino oxide–amide backbone and a straight-chain alkyl spacer was developed. These C2-symmetric chiral N,N′-dioxide ligands could be straightforwardly synthesized from readily available amino acids and amines. They act as neutral tetradentate ligands to bind a wide variety of metal ions. Non-planar cis-α M(N,N′-dioxide) complexes enable an intriguing and easily fine-tuned chiral platform for a number of asymmetric reactions. Privileged N,N′-dioxide ligands frequently show wide substrate generality and exceptional levels of stereocontrol for a specific catalytic reaction. We describe approaches to the ligand design and synthesis, structure and bonding in coordination complexes, and the recent developments in asymmetric catalysis.

Recent advances in positional-selective alkenylations: removable guidance for twofold C–H activation

Abstract: The transition metal-catalyzed transformation of otherwise inert C–H bonds into substituted alkenes offers a versatile tool for the synthesis of value added olefinic molecules. Recent developments in the directing group assisted C–H activation approach ensured high levels of positional selectivity. A vast number of coordinating groups have been utilized in directed C–H alkenylation, which are often not removable after the desired transformation. However, the concept of easily removable or traceless directing group strategy overcomes this limitation and enables site-selective C–H alkenylation of relevance to academia and the practitioners in industry. Various easily removable or transformable directing groups utilized in the transition metal-catalyzed oxidative C–H alkenylations are discussed in this review until February 2017.