LongLarf

Expanding the library: A three‐component cross‐coupling reaction of boronic acid, sodium metabisulfite, and dimethyl carbonate is efficiently established for the construction of an aryl methyl sulfone library. Pharmaceutical synthesis and late‐stage diversification are afforded through this protocol.

Abstract

A three‐component cross‐coupling protocol of boronic acid, sodium metabisulfite, and dimethyl carbonate was developed for the construction of significant functional methyl sulfones, in which introduction of sulfur dioxide at the last stage was successfully achieved in one step. Inorganic sodium metabisulfite was used as an eco‐friendly sulfur dioxide source. Green dimethyl carbonate was employed as methyl reagent in this transformation. Diverse functional methyl sulfones were obtained from various readily available boronic acids. Notably, the last‐stage modification of pharmaceuticals and the synthesis of Firocoxib were efficiently established through this strategy.

Flying squirrels are secretly pink

Flying squirrels are secretly pink, Published online: 28 January 2019; doi:10.1038/d41586-019-00307-6

Keep on POPping! Porous organic polymers (POPs) with high surface area, chemical stability, nanoscale porosity and structural diversity have huge potential as selective CO₂ adsorbent and catalysis for the CO₂ fixation reactions. This review provides a brief account in designing POPs and their application in CO₂ adsorption and fixation for the synthesis of fuels and value added fine chemicals.

Abstract

To overcome the challenges of global warming and environmental pollution it is mandatory to reduce the concentration of atmospheric carbon dioxide (CO₂), which is largely accumulated in air through the combustion of fossil fuels. Thus, sequestration of CO₂ through physisorption on solid adsorbents and their successful conversion into value added fine chemicals are the major priority areas of research today. Innovation of efficient solid CO₂‐philic adsorbents together with their high mechanical/chemical stability and regeneration efficiency are the most challenging objectives to achieve this goal. In this context, porous organic polymers (POPs) owing to their high specific surface area, chemical stability, nanoscale porosity and structural diversity have huge potential to play as selective CO₂ adsorbent. POPs synthesized through large varieties of reactive monomers via simple and convenient chemical routes can be the ideal adsorbents for the CO₂ storage and fixation reactions. A wide range of POPs can be synthesized from different multidentate amines, aldehydes, carboxylic acids or triazine monomers through the polycondensation reactions or solid state condensation reactions. Ease of synthesis, uniform pore width together with high surface area and surface basic sites (nitrogen and other heteroelements) play crucial role in the CO₂ absorption and conversion reactions. This review provides a concise account in designing POPs and their application in CO₂ adsorption and fixation into reactive organic molecules for the synthesis of fuels and value added fine chemicals.

Textbook answer! A sustainable and generalized route for production of amides (up to 21 examples) is developed from selective aerobic oxidations of amines over a non‐noble MnO_x nanorod catalyst. More importantly, this catalyst is leaching‐free, stable, and reusable, outperforming the state‐of‐the‐art heterogeneous catalysts such as Ru(OH)_x/Al₂O₃.

Abstract

The development of heterogeneous catalysts for the synthesis of pharmaceutically relevant compounds is always important for chemistry research. Here, we report a selective aerobic oxidation of aromatic and aliphatic amines to corresponding amides over a nanorod manganese oxide (NR‐MnO_x) catalyst. The kinetic studies reveal that the NR‐MnO_x catalyzed amine‐to‐amide reaction proceeds the oxidative dehydrogenation of the amines into nitriles, followed by hydrolysis of nitrile into amides. The NR−MnO_x exhibits fast kinetics and high selectivities in these steps, as well as hinders the by‐product formation. More importantly, the NR‐MnO_x catalyst is stable and reusable in the continuous recycle tests with water as a sole by‐product, exhibiting superior sustainability and significant advancement to outperform the traditional amide production route in acidic or basic media with toxic by‐products.

The hydrogen shuffle: Transfer of hydrogens from 1,4‐cyclohexadiene to a variety of alkenes is catalyzed by simple alkaline‐earth metal amides. The proposed mechanism for this convenient and highly selective transfer hydrogenation is supported by DFT calculations.

Abstract

The alkene transfer hydrogenation (TH) of a variety of alkenes has been achieved with simple AeN′′₂ catalysts [Ae=Ca, Sr, Ba; N′′=N(SiMe₃)₂] using 1,4‐cyclohexadiene (1,4‐CHD) as a H source. Reaction of 1,4‐CHD with AeN′′₂ gave benzene, N′′H, and the metal hydride species N′′AeH (or aggregates thereof), which is a catalyst for alkene hydrogenation. BaN′′₂ is by far the most active catalyst. Hydrogenation of activated C=C bonds (e.g. styrene) proceeded at room temperature without polymer formation. Unactivated (isolated) C=C bonds (e.g. 1‐hexene) needed a higher temperature (120 °C) but proceeded without double‐bond isomerization. The ligands fully control the course of the catalytic reaction, which can be: 1) alkene TH, 2) 1,4‐CHD dehydrogenation, or 3) alkene polymerization. DFT calculations support formation of a metal hydride species by deprotonation of 1,4‐CHD followed by H transfer. Convenient access to larger quantities of BaN′′₂, its high activity and selectivity, and the many advantages of TH make this a simple but attractive procedure for alkene hydrogenation.

Publication date: 22 March 2019

Source: Tetrahedron, Volume 75, Issue 12

Author(s): Ze-Shui Liu, Guangyin Qian, Qianwen Gao, Peng Wang, Hong-Gang Cheng, Yu Hua, Qianghui Zhou

Graphical abstract

Cooperativity has become a mainstay in the context of multicatalytic reaction design. The combination of two or more catalysts, possessing mechanistically distinct activation principles, within a single chemical setting can enable bond constructions that would be impossible for either of the catalysts alone. An emerging subdomain within the field of multicatalysis are single‐electron transfer processes that are sustained by the synergistic merger of sulfur as well as selenium organocatalysis with photoredox catalysis. From a synthetic viewpoint, such processes bear tremendous value, as they offer new and economic pathways for the concise assembly of complex molecular architectures. Thus, the aim of this Minireview is to highlight recent methodological progress made in this area and to contextualize representative transformations with the mechanistic underpinnings that are enabling these reactions.

Copper to the rescue: A general method for the synthesis of propargylic sulfones featuring quaternary stereocenters has been developed. The method relies on a copper‐catalyzed sulfonylation of propargylic cyclic carbonates using sodium sulfinates. It provides the first example of such a transition‐metal‐catalyzed enantioselective propargylic substitution reaction with sulfur‐centered nucleophiles and gives access to functionalized tertiary sulfones.

Abstract

Tertiary propargylic sulfones are of significant importance in organic synthesis and medicinal chemistry, but to date no general asymmetric synthesis approach has been developed. We disclose a versatile copper‐catalyzed sulfonylation of propargylic cyclic carbonates using sodium sulfinates that allows the construction of propargylic sulfones featuring elusive quaternary stereocenters. This method provides the first successful example of such an enantioselective propargylic sulfonylation, features high asymmetric induction, wide functional group tolerance, and scalability, and enables attractive product diversification.

All in one‐component: A Lewis‐acidic metal center, a functionalized ligand containing hydrogen bond donors, and a nucleophilic halide all work efficiently in one catalyst, Fe^II–iminopyridine and bisiminopyridine complexes, through a well‐organized structure. The formation of cyclic carbonates occurs from epoxides and carbon dioxide under mild conditions in a single‐component, cocatalyst‐free system.

Abstract

The use of multifunctional and sustainable Fe catalysts for the formation of cyclic carbonates from epoxides and carbon dioxide at 80 °C and 3 bar pressure is presented. The optimal catalyst possesses a halide counteranion and a hydrogen bond donor to activate the epoxide for ring opening, affording a single‐component, cocatalyst‐free catalytic system.

Green nylon: Use of 25 % ZrO₂/SiO₂ as catalyst allows the gas‐phase ring‐opening of bio‐based γ‐valerolactone with methanol to a mixture of methyl pentenoates containing 81 % of the 4‐isomer, which could be selectively hydroformylated from the mixture to methyl 5‐formyl‐valerate, an intermediate for ϵ‐caprolactam. The remaining isomers were converted into dimethyl adipate.

Abstract

Use of ZrO₂/SiO₂ as a solid acid catalyst in the ring‐opening of biobased γ‐valerolactone with methanol in the gas phase leads to mixtures of methyl 2‐, 3‐, and 4‐pentenoate (MP) in over 95 % selectivity, containing a surprising 81 % of M4P. This process allows the application of a selective hydroformylation to this mixture to convert M4P into methyl 5‐formyl‐valerate (M5FV) with 90 % selectivity. The other isomers remain unreacted. Reductive amination of M5FV and ring‐closure to ϵ‐caprolactam in excellent yield had been reported before. The remaining mixture of 2‐ and 3‐MP was subjected to an isomerising methoxycarbonylation to dimethyl adipate in 91 % yield.

Innovations in synthetic chemistry have enabled the discovery of many breakthrough therapies that have improved human health over the past century. In the face of increasing challenges in the pharmaceutical sector, continued innovation in chemistry is required to drive the discovery of the next wave of medicines. Novel synthetic methods not only unlock access to previously unattainable chemical matter, but also inspire new concepts as to how we design and build chemical matter. We identify some of the most important recent advances in synthetic chemistry as well as opportunities at the interface with partner disciplines that are poised to transform the practice of drug discovery and development.

Water lends a helping hand: The anti‐Markovnikov hydroazidation of alkenes has been accomplished under visible‐light irradiation by using [Ir(dF(CF₃)ppy)₂(dtbbpy)]PF₆ as the photocatalyst and trimethylsilyl azide as the azidating agent. The reactions were significantly facilitated by water, the beneficial effect of which can be attributed to its participation in the reaction as the hydrogen donor.

Abstract

The anti‐Markovnikov hydroazidation of alkenes has been accomplished under visible‐light irradiation by using [Ir(dF(CF₃)ppy)₂(dtbbpy)]PF₆ as the photocatalyst and trimethylsilyl azide as the azidating agent. The reactions were greatly facilitated by water, the beneficial effect of which can be attributed to its participation in the reaction as the hydrogen donor, as indicated by deuterium isotope experiments. The reactions proceed under solvent free conditions in the presence of water. 4‐Dimethylaminopyridine also exhibited a beneficial effect on the reactions. The present method enabled hydroazidation of several types of unactivated alkenes with good yields and high regioselectivity.

Abstract

Tris(pentafluorophenyl)borane‐catalyzed C−C bond functionalization of arylallyl alcohols using donor‐acceptor carbenes is presented. The allylic hydroxyl group is found to assist the product formation by neighboring group participation providing a clue towards mechanistic understanding. This method can also be employed to effect homologation of allyl alcohols to homoallyl alcohols. Overall, this metal‐free transformation presents a novel disconnection strategy towards carbon‐carbon bond scission and formation.