渡邉 康平

To the best of our knowledge, enzymes that catalyse intramolecular Diels-Alder ([4+2] cycloaddition) reactions are frequently reported in natural product biosynthesis; however, no native enzymes utilising Lewis acid catalysis have been reported. Verticilactam is a representative member of polycyclic macrolactams, presumably produced by spontaneous cycloaddition. We report that the intramolecular [4+2] cycloadditions can be significantly accelerated by ferredoxins (Fds), a class of small iron-sulphur (Fe-S) proteins. Through iron atom substitution by Lewis acidic gallium (Ga) iron and computational calculations, we confirm that the ubiquitous Fe-S cluster efficiently functions as Lewis acid to accelerate the tandem [4+2] cycloaddition and Michael addition reactions by lowering free energy barriers. Our work highlights Nature's ingenious strategy to generate complex molecule structures using the ubiquitous Fe-S protein. Furthermore, our study sheds light on the future design of Fd as a versatile Lewis acid catalyst for [4+2] cycloaddition reactions.

We describe a concise and reliable protocol for the precisely controlled tetradeuteration of straight-chain fatty acids (FAs) at the α- and β-positions that is generally applicable to a variety of FAs, including trans-FAs, polyunsaturated FAs (PUFAs), and their oxidized derivatives. The precisely controlled introduction of four deuterium atoms into the FAs enables their persistent and quantitative tracking by LC-MS/MS analysis based on their molecular structures. In addition, the phosphatidylcholine (PC) species prepared from the tetradeuterated FAs thus obtained give a diagnostic peak, namely, a phosphocholine fragment that contains deuterium, in the LC-MS/MS analysis. With these features, the metabolism of a representative oxidized linoleic acid, that is, hydroxyoctadecadienoic acid (HODE), was investigated, leading to the identification of acyltransferases that transfer the acyl moiety derived from HODE to lysophosphatidylcholine.

Abstract A protocol for regio‐controlled hydromagnesiation of 1,3‐enynes was developed using magnesium hydride that is generated in situ by solvothermal treatment of sodium hydride (NaH) and magnesium iodide (MgI₂) in THF. The resulting allenylmagnesium species could be converted into tri‐ and tetra‐substituted allenes by subsequent treatment with various carbon‐ and silicon‐based electrophiles with the aid of CuCN as a catalyst.

Abstract We report a protocol for aryl cross‐coupling of electron‐deficient aryl halides with electron‐rich (hetero)arenes that is driven solely by violet light. This process takes advantage of formation of photo‐excited state of electron‐deficient aryl halides, that are reduced by electron‐rich (hetero)arenes to form a pair of aryl anion and cation radicals. The resulting aryl anion radicals of aryl halides undergo mesolysis of the carbon‐halogen bond to generate aryl radicals, that are coupled most likely with aryl cation radicals to afford functionalized biaryls. magnified image

<p>Copper(<sc>i</sc>)/sucrose-catalyzed hydroxylation of aryl halides in neat water has been developed. The dual role of sucrose, the reaction pathway, and the high selectivity were investigated using a combination of experimental and theoretical techniques.</p>

The methoxy group is generally considered as a poor leaving group for nucleophilic substitution reactions. This work verified the superior ability of the methoxy group in nucleophilic amination of arenes mediated by the sodium hydride and lithium iodide through experimental and computational approaches.

The 7‐allylated benzofuran derivatives were synthesized via a continuous reaction of Claisen rearrangement and annulation using o‐allyloxyetynylbenzene as starting material. In addition, it was observed that annulation of o‐alkynylphenol proceeded under mild conditions when carried out in the presence of a catalytic amount of TBAF. Furthermore, these continuous reactions could be achieved in a one‐pot reaction and afforded not only 7‐allylbenzofurans but also 7‐alkenylbenzofurans by controlling the reaction temperature and time of the annulation. Finally, we demonstrated that 7‐allylbenzofuran and 7‐alkenylbenzofuran could be converted into 7‐(2‐formylvinyl)benzofuran and 7‐formylbenzofuran derivatives, respectively. Therefore, various 7‐substituted benzofuran derivatives could be synthesized according to this synthetic strategy.

<p>The unsaturated vicinal P/B FLP obtained from the unusual 1,1-hydroboration of dimesitylphosphino(trimethylsilyl)acetylene with Piers’ borane serves as an ambiphilic ligand in gold(i) chemistry.</p>

ABSTRACT Thioxanthone–anthracene‐9‐carboxylic acid (TX‐ANCA) namely 14‐oxo‐14H‐naphthol [2,3‐b]thioxanten‐12‐carboxylic acid, is synthesized and characterized as part of our continuing interest for syntheses of polyaromatic initiators. Photoinitiator, TX‐ANCA have good absorption properties in the UV and visible region of the electromagnetic spectrum (ɛ₃₇₀: 9080 M⁻¹cm⁻¹, ɛ₄₃₀: 6151 M⁻¹ cm⁻¹). The fluorescence quantum yield is calculated as 0.1 which is slightly higher than of the parent thioxanthone compound (φ_f: 0.07). The phosphorescence lifetime is found to be 39 ms. The possible initiating mechanism of TX‐ANCA is based on photoexcitation of TX‐ANCA and quenching of triplet excited states of TX‐ANCA by molecular oxygen generates singlet oxygen. Singlet oxygen reacts with the anthracene moiety of TX‐ANCA possibly forms an endoperoxide. The endoperoxides undergoes photochemical or thermal decomposition to form radicals which are able to initiate free radical polymerization. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1878–1883

<p>The hydrazone–palladium catalyzed direct intermolecular reaction of o-alkynylphenols with allylic acetates gave the corresponding 2-substituted-3-allylbenzofuran derivatives at room temperature.</p>

We have found that Suzuki–Miyaura‐type reactions of dibromoalkenes with arylboronic acids using a hydrazone–Cu catalyst system proceeded smoothly under mild conditions to afford the corresponding internal alkyne derivatives in good yields. Furthermore, we also succeeded in the synthesis of o‐allyloxy(ethynyl)benzene derivatives, which are known to be effective precursors of various heterocyclic compounds, through this reaction.

We have found that Suzuki–Miyaura‐type reactions of o‐allyloxy(bromoethynyl)benzenes with arylboronic acids using a hydrazone/Cu catalyst system proceeded smoothly in iPrOH under mild conditions to afford the corresponding o‐allyloxy(arylethynyl)benzene derivatives in good yields without decomposition of the allyloxy group. We have further demonstrated that annulation and enyne metathesis of the o‐allyloxy(arylethynyl)benzene derivatives using transition‐metal catalysts led to various heterocyclic compounds.

<p>The annulation of 1-cinnamyloxy-2-ethynylbenzene derivatives using a hydrazone–palladium catalyst system proceeded smoothly and gave the corresponding 2-substituted-3-cinnamylbenzofurans in good-to-excellent yields.</p>

<p>Annulation of 1-allyl-2-bromobenzene derivatives with internal alkynes using a hydrazone–palladium catalyst afforded polysubstituted naphthalene derivatives in good to high yields.</p>

Abstract We report a new catalyst system, morpholine–NiCl₂, for the Suzuki–Miyaura coupling of aryl chlorides with aryl‐ or alkenylboronic acids to give biaryl compounds. This catalyst system is easy to apply on a large scale because of its easy preparation and the use of inexpensive reagents. In addition, analysis of the residual nickel shows only 9.7 ppm remaining after normal work‐up. This catalyst system has been applied to 26 compounds to give a variety of biaryl products, including hetero‐biaryl compounds.

Abstract We report a new catalyst system, a morpholine–Pd(OAc)₂ complex, for Suzuki–Miyaura coupling of aryl tosylates or mesylates with arylboronic acids to give biaryl compounds. The morpholine–Pd(OAc)₂ catalyst system is proposed to be a precursor of the catalytically active species in the coupling reaction. Aryl chlorides and aryl triflates can also be used in this coupling reaction. Altogether, 22 biaryl compounds were obtained using this catalyst system.