The promising aspects of iron in synthetic chemistry are being explored for three-four decades as a green and eco-friendly alternative to late transition metals. This present review unveils these rich iron-chemistry towards different transformations.

The ubiquity of carbon halogen bonds in the structural core of numerous biomolecules and pharmaceuticals along with their role as synthetic precursors in various organic reactions makes the organic halides a crucial class of organic compounds. Consequently, the synthesis of organic halides with high regioselectivity is of paramount importance in synthetic chemistry. In nature, selective halogenation is achieved by metalloenzymes with high efficiency involving high-valent iron-oxo as active species. The high selectivity of halogenating enzymes attracted considerable attention leading to the development of several biomimetic approaches for CÀ H halogenation. Moreover, the emergence of transition metal (TM) catalyzed site-selective CÀ H halogenation protocols through the development of several directed strategies has also been impressive. There has been significant development in the first row TM catalyzed CÀ H halogenation reactions despite the dominance of late transition metals catalysts in this field. But in literature, there is no up-to-date recent review article that consolidates bio-mimetic as well as synthetic strategies of CÀ H halogenation (X = Cl, Br, I) containing organo-fluorination with all the first-row transition metals. Thus, we got motivated and have focused to elucidate the recent developments of first row TM-catalyzed CÀ H halogenation of (hetero)arenes and alkanes through biomimetic approaches as well as directed and undirected strategies in this present review. Additionally, this review covers the recent progresses in the CÀ H fluorination methodologies. Altogether, the review will provide a combined overview of all the strategies of first-row transition-metalmediated CÀ H halogenation reactions that may benefit the scientific community towards the development of new methodologies in this field.

The oxygen atom transfer (OAT)r eactivity of the non-heme [Fe IV (2PyN2Q)(O)] 2+ (2)c ontaining the sterically bulky quinoline-pyridine pentadentate ligand (2PyN2Q) has been thoroughly studied with different olefins.T he ferryl-oxo complex 2 shows excellent OATreactivity during epoxidations. The steric encumbrance and electronic effect of the ligand influence the mechanistic shuttle between OATpathway Iand isomerization pathwayI I(during the reaction stereo pure olefins), resulting in amixture of cis-trans epoxide products.In contrast, the sterically less hindered and electronically different [Fe IV (N4Py)(O)] 2+ (1)p rovides only cis-stilbene epoxide. A Hammett study suggests the role of dominant inductive electronic along with minor resonance effect during electron transfer from olefin to 2 in the rate-limiting step.Additionally, ac omputational study supports the involvement of stepwise pathwaysduring olefin epoxidation. The ferryl bend due to the bulkier ligand incorporation leads to destabilization of both d z 2 and d x 2 Ày 2 orbitals,l eading to av ery small quintet-triplet gap and enhanced reactivity for 2 compared to 1.Thus,the present study unveils the role of steric and electronic effects of the ligand towards mechanistic modification during olefin epoxidation Scheme 1. Olefin epoxidation by [Fe IV (2PyN2Q)(O)] 2+ (2), quinolinepyridine containing ligand backbone. [

The oxygen atom transfer (OAT)r eactivity of the non-heme [Fe IV (2PyN2Q)(O)] 2+ (2)c ontaining the sterically bulky quinoline-pyridine pentadentate ligand (2PyN2Q) has been thoroughly studied with different olefins.T he ferryl-oxo complex 2 shows excellent OATreactivity during epoxidations. The steric encumbrance and electronic effect of the ligand influence the mechanistic shuttle between OATpathway Iand isomerization pathwayI I(during the reaction stereo pure olefins), resulting in amixture of cis-trans epoxide products.In contrast, the sterically less hindered and electronically different [Fe IV (N4Py)(O)] 2+ (1)p rovides only cis-stilbene epoxide. A Hammett study suggests the role of dominant inductive electronic along with minor resonance effect during electron transfer from olefin to 2 in the rate-limiting step.Additionally, ac omputational study supports the involvement of stepwise pathwaysduring olefin epoxidation. The ferryl bend due to the bulkier ligand incorporation leads to destabilization of both d z 2 and d x 2 Ày 2 orbitals,l eading to av ery small quintet-triplet gap and enhanced reactivity for 2 compared to 1.Thus,the present study unveils the role of steric and electronic effects of the ligand towards mechanistic modification during olefin epoxidation Scheme 1. Olefin epoxidation by [Fe IV (2PyN2Q)(O)] 2+ (2), quinolinepyridine containing ligand backbone. [

Ruthenium‐catalyzed direct C(sp 2 )H bond amidation has emerged as a convenient synthetic tool for the synthesis of bioactive and active pharmaceutical molecules. Different directing groups (DGs) including hetero‐arenes, carbonyl groups are used for ortho ‐ amidations that lead to the synthesis of functionalized amine and amides. The easily removable methyl‐phenyl sulfoximine (MPS) has been found to be very effective in case of carboxylic acids whereas transient DG strategy was effective for weakly coordinating benzaldehydes. These methods have been applied for the synthesis of important life‐saving drug molecules. In this article, we have discussed the ruthenium‐catalyzed direct amidation of C(sp 2 )H bonds of arenes with mechanistic elucidations.