Concise synthesis of heliolactone, a non-canonical strigolactone isolated from sunflower

Heliolactone is one of the earliest identified non-canonical strigolactones. Its concise synthesis was achieved by employing Knoevenagel-type condensation and semi-reduction of a malonate intermediate as the key steps. This synthesis was performed in a non-stereoselective manner, and thus a racemic and diastereomeric mixture of heliolactone was obtained. The developed synthetic route is fairly concise and straightforward. Graphical abstract A racemic and diastereomeric mixture of heliolactone was synthesized.</p

C–H Triflation of BINOL Derivatives Using DIH and TfOH

C–H trifluoromethane­sulfonyloxylation (triflation) of 1,1′-bi-2-naphthol (BINOL) derivatives has been established under mild conditions using 1,3-diiodo-5,5-dimethyl­hydantoin (DIH) and trifluoromethane­sulfonic acid (TfOH). Up to eight TfO groups can be introduced in a single operation. The resulting highly oxidized BINOL derivatives can be successfully converted to 8,8′-dihydroxy BINOL and bisnaphtho­quinone compounds. Mechanistic studies suggested that C–H triflation occurs in the form of an aromatic substitution reaction via the in situ formation of a radical cation

Defect Structure Analysis of Heterointerface between Pt and CeO_<i>x</i> Promoter on Pt Electro-Catalyst

Pt–CeO_<i>x</i>/C (1.5 ≤ <i>x</i> ≤ 2) electro-catalyst is one of the most promising cathode materials for use in polymer membrane electrolyte fuel cells. To clarify the microstructure of Pt–CeO_<i>x</i> heterointerface, we prepared Pt-loaded CeO_<i>x</i> thin film on conductive SrTiO₃ single crystal substrate by using a stepwise process of pulse laser deposition method for the preparation of epitaxial growth CeO_<i>x</i> film followed by an impregnation method which loaded the Pt particles on the CeO_<i>x</i> film. The electrochemistry observed for the Pt-loaded CeO_<i>x</i> thin film on the conductive single crystal substrate was examined by using cyclic voltammetry in 0.5 M H₂SO₄ aqueous solution, and a cross-sectional image of the aforementioned Pt–CeO_<i>x</i> thin film electrode was observed using a transmission electron microscope. The electrochemistry observed for Pt–CeO_<i>x</i> thin film electrode clearly showed the promotion effect of CeO_<i>x</i>. Also, the microanalysis indicated that unique, large clusters that consisted of C-type rare-earth-like structures were formed in the Pt–CeO_<i>x</i> interface by a strong interaction between Pt and CeO_<i>x</i>. The present combination analysis of the electrochemistry, microanalysis, and atomistic simulation indicates that the large clusters (i.e., 12 (Pt_Ce′′–Vo^••) + 2 (Pt_Ce′′–2Vo^••–2Ce_Ce′)) that were formed into the Pt–CeO_<i>x</i> interface promoted the charge transfer between Pt surface and CeO_<i>x</i>, suggesting that the oxygen reduction reaction activity on Pt can be maximized by fabrication of C-type rare-earth-like structure that consists of the aforementioned large clusters in the Pt–CeO_<i>x</i> interfaces

Active Pt-Nanocoated Layer with Pt–O–Ce Bonds on a CeO_<i>x</i> Nanowire Cathode Formed by Electron Beam Irradiation

A Pt-nanocoated layer (thickness of approx. 10–20 nm) with Pt–O–Ce bonds was created through the water radiolysis reaction on a CeOx nanowire (NW), which was induced by electron beam irradiation to the mixed suspension of K2PtCl4 aqueous solution and the CeOx NW. In turn, when Pt-nanocoated CeOx NW/C (Pt/C ratio = 0.2) was used in the cathode layer of a membrane electrode assembly (MEA), both an improved fuel cell performance and stability were achieved. The fuel cell performance observed for the MEA using Pt-nanocoated CeOx NW/C with Pt–O–Ce bonds, which was prepared using the electron beam irradiation method, improved and maintained its performance (observed cell potential of approximately 0.8 V at 100 mW cm–2) from 30 to 140 h after the start of operation. In addition, the activation overpotential at 100 mA cm–2 (0.17 V) obtained for MEA using Pt-nanocoated CeOx NW/C was approximately half of the value at 100 mA cm–2 (0.35 V) of MEA using a standard Pt/C cathode. In contrast, the fuel cell performance (0.775 V at 100 mW cm–2 after 80 h of operation) of MEA using a nanosized Pt-loaded CeOx NW (Pt/C = 0.2), which was prepared using the conventional chemical reduction method, was lower than that of MEA using a Pt-nanocoated CeOx/C cathode and showed reduction after 80 h of operation. It is considered why the nanocoated layer having Pt–O–Ce bonds heterogeneously formed on the surface of the CeOx NW and the bare CeO2 surface consisting of Ce4+ cations would become unstable in an acidic atmosphere. Furthermore, when a conventional low-amount Pt/C cathode (Pt/C = 0.04) was used as the cathode layer of the MEA, its stable performance could not be measured after 80 h of operation as a result of flooding caused by a lowering of electrocatalytic activity on the Pt/C cathode in the MEA. In contrast, a low-amount Pt-nanocoated CeOx NW (Pt/C = 0.04) could maintain a low activation overpotential (0.22 V at 100 mA cm–2) of MEA at the same operation time. Our surface first-principles modeling indicates that the high quality and stable performance observed for the Pt-nanocoated CeOx NW cathode of MEA can be attributed to the formation of a homogeneous electric double layer on the sample. Since the MEA performance can be improved by examining a more effective method of electron beam irradiation to all surfaces of the sample, the present work result shows the usefulness of the electron beam irradiation method in preparing active surfaces. In addition, the quantum beam technology such as the electron beam irradiation method was shown to be useful for increasing both performance and stability of fuel cells