Hydroxyl-Assisted and Co(III)-Catalyzed Redox-Neutral C-H Activation/Directing Group Migration of 2-Pyridones with Propargyl Alcohols: Synthesis of Tetrasubstituted Alkenes

This study provides a practical route to synthesize tetrasubstituted alkenes that involves Co(III)-catalyzed C-H bond activation and regioselective insertion of the alkyne, followed by chelation of the substrate hydroxyl to Co and migration of the pyridine group. Density functional theory studies revealed the origin of regioselectivity and elucidated the crucial role of the hydroxyl group for the migration of pyridine. The method can be conducted on a gram scale, is compatible with a wide range of substrates, and has a high functional group tolerance. To demonstrate its significance, the method was used for the late-stage modification of Fasudil. Furthermore, the synthetic significance of the method was demonstrated by the various derivatizations of the products, many of which exhibit intriguing fluorescence characteristics.

When the Study of the Post-Synthetic Modification Method on a 1D Spin Crossover Coordination Polymer Highlights its Catalytic Activity

We are interested in studying the catalytic activity of the spin crossover (SCO) complex ([Fe(NH2trz)3](NO3)2). In this work, we demonstrate that, by adapting the experimental conditions, we can switch from a quantitative post-synthetic modification (PSM) reaction to the use of this complex as a catalyst for the formation of imine from 4-amino-1,2,4-triazole. During the catalytic reaction, the iron complex undergoes two different PSM reactions: the first is the action of the aldehyde on the NH2 groups present on the complex, whereas the second PSM reaction occurs between the imine complex and aminotriazole, leading back to the starting complex. These two PSM reactions are at least partially involved in the catalytic mechanism. Furthermore, the combination of these two PSM reactions enables us to modulate the particle size and shape of the final amine complex without altering its excellent SCO properties. This result is of interest in the field of heterogeneous catalysis, where particle size has a strong influence on the catalytic activity, and for the proper integration in devices for different applications.

Iron-catalyzed cascade C-C/C-O bond formation of 2,4-dienals with donor-acceptor cyclopropanes: access to functionalized hexahydrocyclopentapyrans

Iron-catalyzed cascade C-C and C-O bond formation of 2,4-dienals with donor-acceptor cyclopropanes (DACs) has been developed to furnish hexahydrocyclopentapyrans. Optically active DACs can be coupled stereospecifically (>97% ee). Chirality transfer, use of iron-catalysis and substrate scope are the salient practical features.

Recent advances in iron-catalysed coupling reactions for the construction of the C(sp2)-C(sp2) bond

The advancement of transition-metal-catalyzed coupling reactions has been demonstrated as a highly effective strategy for the formation of carbon-carbon bonds, which serve as the fundamental basis for organic synthetic chemistry. Given that iron represents one of the most economical and ecologically sustainable metallic elements available, the exploration and enhancement of iron-catalysed coupling reactions have garnered increasing interest within the scientific community. In recent years, numerous iron-catalysed reactions have been reported, showcasing their efficacy in establishing C-C bonds. In this minireview, we present a systematic analysis of C(sp²)-C(sp²) bond formation via iron-catalysed coupling reactions as documented in the extant literature.

Stereoselective Semi-Hydrogenations of Alkynes by First-Row (3d) Transition Metal Catalysts

The chemo- and stereoselective semi-hydrogenation of alkynes to alkenes is a fundamental transformation in synthetic chemistry, for which the use of precious 4d or 5d metal catalysts is well-established. In mankind's unwavering quest for sustainability, research focus has considerably veered towards the 3d metals. Given their high abundancy and availability as well as lower toxicity and noxiousness, they are undoubtedly attractive from both an economic and an environmental perspective. Herein, we wish to present noteworthy and groundbreaking examples for the use of 3d metal catalysts for diastereoselective alkyne semi-hydrogenation as we embark on a journey through the first-row transition metals.

A library of new bifunctional alkenes obtained by a highly regiodivergent silylation of 1,5-hexadiene

An efficient methodology for the synthesis of two groups of silicon-containing alkenes is reported. It includes a highly regioselective functionalization of 1,5-hexadiene through hydrosilylation and dehydrogenative silylation with organofunctional silanes and siloxanes. The established conditions enable selective monofunctionalization of 1,5-hexadiene regardless of the organosilicon modifier used as well as the type of functional group bonded to the silicon-based compound. All products were isolated and fully characterized by NMR spectroscopy and MS techniques.

Metal-free enaminone C-N bond cyanation for the stereoselective synthesis of (E)- and (Z)-β-cyano enones

A highly practical method for C-CN bond formation by C-N bond cleavage on enaminones leading to the efficient synthesis of β-cyano enones is developed. The reactions take place efficiently to provide (E)-β-cyano enones with only a molecular iodine catalyst. In addition, the additional employment of oxalic acid enables the selective synthesis of (Z)-β-cyano enones.

Dual Palladium/Copper-Catalyzed anti-Selective Intermolecular Allenylsilylation of Terminal Alkynes: Entry to (E)-Silyl Enallenes

A palladium-/copper-cocatalyzed three-component trans-allenylsilylation of terminal alkynes with propargyl acetates and PhMe₂SiBpin is described, which is driven by the regioselective allenylation of the alkyne with propargyl acetates and then silylation. This method allows the simultaneous incorporation of an allene and silicon across the C≡C bond and provides a highly chemo-, regio-, and stereoselective alkyne difunctionalization route to the synthesis of valuable (E)-silyl enallenes. The utility of this method is highlighted by late-stage derivatization of bioactive compounds.

Fe-Catalysed Coupling Reactions Between Alkynes and Alcohols

In this review, we discussed about the synthetic developments in the field of Fe-catalysis for the formation of - bonds through the coupling of alkynes and alcohols, for the period of 13 years (2008-2020). These strategies fulfil important Green Chemistry principles, as they are highly atom economic (up to 100 %), no toxic by-products (only water), employs highly abundant and low toxic alcohols (no need for any pre-functionalization hence step economy) and cheaper Fe-catalysts. Having these advantages, one can predict that in the coming years a large number of fascinating new iron-catalyzed reactions will be developed for the organic synthesis. We hope that this review article will be highly useful for the synthetic community to design and develop new Fe-catalyzed coupling reactions and keeps the content in the right prospect.

1,3-Difunctionalization of alkenes: state-of-the-art and future challenges

This review summarizes the advances in 1,3-difunctionalization of alkenes mediated by Pd-, Ni-, Fe-, and Cu-based catalysts, as well as under metal-free conditions, with an emphasis on the reaction mechanisms and factors governing regioselectivity.