Dielectric response of (KBr)1−x(KCN)x dilute compounds — distribution of relaxation times

We argue on the dielectric response of the (KBr)_1?x(KCN)_x dilute compounds in relation to the reorientation processes of the CN^? ions. In these compounds the distribution of the activation energies of such processes is naturally expected. This distribution leads to the distribution of the dielectric relaxation times whose width strongly depends on temperature. This is in agreement with the experiments.     

A new chiral recognition in aminolysis of 3-acyl-4(r)-methoxycarbonyl-1,3-thiazolidine-2-thione with racemic amines

A chiral recognition was observed in aminolysis of 3-acyl-4(R)-methoxycarbonyl-1,3-thiazolidine-2-thione $\text{1}$ by racemic amine $\text{2}$ to give an optically active amide (S-excess) and amine (R-excess).     

Direct generation of Ti-enolate of alpha-CF3 ketone: theoretical study and high-yielding and diastereoselective Aldol reaction

Success in the direct generation of the Ti-enolate of alpha-CF3 ketone and its aldol reaction is reported. The importance of Ti-F interaction during the course of the reaction is also reported.     

Electron-spin polarization of photoions produced through photoionization from the laser-excited triplet state of Sr

We report the detailed experimental study on the production of electron-spin-polarized Sr+ ions through one-photon resonant two-photon ionization via laser-excited 5s5p 3P1 (MJ = +1) of Sr atoms produced by laser-ablation. We have experimentally confirmed that the use of laser-ablation for the production of Sr atoms prior to photoionization does not affect the electron-spin polarization. We have found that the degree of electron-spin polarization is 64+/-9%, which is in good agreement with our recent theoretical prediction. As we discuss in detail, we infer, from a simple analysis, that photoelectrons, being the counterpart of electron-spin-polarized Sr+ ions, have approximately the same degree of electron-spin polarization. Our experimental results demonstrate that the combined use of laser-ablation technique and pulsed lasers for photoionization would be a compact and effective way to realize a pulsed source for spin-polarized ions and electrons for the studies of various spin-dependent dynamics in chemical physics.     

New ring-expansion reactions of hydroxy propenoyl cyclic compounds under palladium(0)/phosphine-catalyzed conditions

[reaction: see text] Palladium(0)-catalyzed one-atom ring-expansion of 1-hydroxy-2,2-dialkyl-1-propenoylindan derivatives has been achieved in the presence of P(o-tolyl)(3) giving 2-hydroxy-3,3-dialkyl-2-vinyl-1-tetralone derivatives in excellent yields. This ring-expansion reaction was applied to a 17-(1-oxo-2-propenyl)-beta-estradiol derivative and furnished a similar ring-expanded product in an excellent yield.     

Mechanistic considerations for the consecutive cyclization of 2,3-dibromopropylamine hydrobromide giving a strained molecule, 1-azabicyclo[1.1.0]butane

The effective formation of 1-azabicyclo[1.1.0]butane (2) by treatment of 2,3-dibromopropylamine hydrobromide (1) with n-BuLi could be understood considering a rational reaction pathway via both transition states 10 and 19 based on the intramolecular Br...Li(+) coordination. A similar cyclization pathway starting from N-benzyl-3-bromopropylamine hydrochloride (17) to afford N-benzylazetidine (18) could also be postulated on the basis of a transition state 20 involving the intramolecular Br...Li(+) coordination.     

Stimuli‐Responsive Dual‐Color Photon Upconversion: A Singlet‐to‐Triplet Absorption Sensitizer in a Soft Luminescent Cyclophane

Reversible emission color switching of triplet–triplet annihilation‐based photon upconversion (TTA‐UC) is achieved by employing an Os complex sensitizer with singlet‐to‐triplet (S‐T) absorption and an asymmetric luminescent cyclophane with switchable emission characteristics. The cyclophane contains the 9,10‐bis(phenylethynyl)anthracene unit as an emitter and can assemble into two different structures, a stable crystalline phase and a metastable supercooled nematic phase. The two structures exhibit green and yellow fluorescence, respectively, and can be accessed by distinct heating/cooling sequences. The hybridization of the cyclophane with the Os complex allows near‐infrared‐to‐visible TTA‐UC. The large anti‐Stokes shift is possible by the direct S‐T excitation, which dispenses with the use of a conventional sequence of singlet–singlet absorption and intersystem crossing. The TTA‐UC emission color is successfully switched between green and yellow by thermal stimulation.     

Catalytic asymmetric synthesis and anticancer effects of the novel non-calcemic analog of vitamin D, 2α-fluoro-19-nor-22-oxa-1α,25-dihydroxyvitamin D3 in metastatic lung carcinoma

1α,25-Dihydroxyvitamin D₃ (1α,25-D₃) has potent antiproliferative and anti-invasive properties in vitro in cancer cells. However, the major limitation to its clinical use is that it causes hypercalcemia. Therefore, vitamin D analogs with potent cell regulatory effects but with weaker calcemic effects than 1α,25-D₃ are required. Among them, 22-oxa-1α,25-D₃ and 19-nor-1α,25-D₃ have anti-cancer effects with relatively low calcemic effects. Modifications at the C-2α position of the A-ring also produced analogs with a unique biological profile. Not only the side-chain but also the A-ring modification thus generates a unique analog with potent cell regulatory effects and low calcemic activity as well. We report here that the hybrid 1α,25-D₃ analog, synthesized via the highly regio- and stereo-selective ring opening 2α-fluorination and catalytic asymmetric carbonyl-ene cyclization, with 2α-fluoro, 19-nor, and 22-oxa modification exhibits unique cell regulatory activities against the development of metastatic lung carcinoma.