Ring-opening fluorination of bicyclic azaarenes

We have discovered a ring-opening fluorination of bicyclic azaarenes. Upon treatment of bicyclic azaarenes such as pyrazolo[1,5-a]pyridines with electrophilic fluorinating agents, fluorination of the aromatic ring is followed by a ring-opening reaction. Although this overall transformation can be classified as an electrophilic fluorination of an aromatic ring, it is a novel type of fluorination that results in construction of tertiary carbon–fluorine bonds. The present protocol can be applied to a range of bicyclic azaarenes, tolerating azines and a variety of functional groups. Additionally, mechanistic studies and enantioselective fluorination have been examined.

A ring-opening fluorination of bicyclic azaarenes was developed. Although this overall transformation can be classified as an electrophilic fluorination of aromatics, it is a novel type of fluorination that results in construction of tert-C–F bonds.     

Estimation of secondary electron effect in the J-PARC rapid cycling synchrotron after first study

The J-PARC 3 GeV rapid-cycling synchrotron (RCS) is required to provide 1 MW pulsed protons to the spallation neutron target and the 50 GeV main ring. Since the RCS finally accelerates very high intensity beam such as 8.3 × 10¹³ ppp, the secondary electron cloud may affect the accelerator performance. We measured the secondary electron emission from the TiN coating surface and the ferrite sample. By using these measurement results, we estimated the effect of the electron cloud made by the emitted secondary electron at present beam parameters.     

Biotransformation of ferulic acid into two new dihydrotrimers by Momordica charantia peroxidase

As a result of a continuing investigation of the biotransformation of ferulic acid with H2O2/Momordica charantia peroxidase at pH 5.0 in the presence of acetone, triFA1 (1) and triFA2 (2), two new FA dehydrotrimers, have been isolated. The structures were elucidated from the spectroscopic data including 2D-NMR such as HSQC, HMBC and NOESY data. TriFA1 (1) is a unique FA dehydrotrimer possessing a 3a,9b-dihydro-1H-furo[3,4-c][1]benzopyran-3(4H)-one ring system. The possible mechanism for the formation of triFA1 was also discussed.     

Laser-induced above-band-gap transparency in GaAs

We report the observation of large (approximately 40%) laser-induced above-band-gap transparency in GaAs at room temperature. The induced transparency is present only during the pulse width of the driving midinfrared laser pulses and its spectral shape is consistent with a laser-induced blueshift of the band edge. Our simulations based on the dynamic Franz-Keldysh effect reproduce the salient features of the experimental results, demonstrating, in particular, that the amount of the band edge shift is approximately given by the ponderomotive potential.