A novel one-pot synthesis of carbazole-1,4-quinones through Pd-catalyzed cyclocarbonylation,desilylation and oxidation processes from 3-iodo-2-propenylindoles

A novel one-pot synthesis of carbazole-1,4-quinone by consecutive Pd-catalyzed cyclocarbonylation, desilylation, and oxidation reactions is described. We propose a possible mechanism of the cyclocarbonylation reaction between 3-iodo-2-propenylindole and CO (1 atm) in the presence of a tributyl(vinyl)tin and Pd-catalyst and the resulting acylpalladium species was directly coupled with a terminal alkene to produce the carbazole-1,4-quinone. To our knowledge, this is the first example of this type of reaction. A new formal total synthesis of a carbazole-1,4-quinone alkaloid, murrayaquinone A was established using this reaction.     

Top-quark-mass enhancement in a seesaw-type quark mass matrix

We investigate the implications of a seesawtype mass matrix, i.e.,M _f?m _LM _F ^?1 m _R, for quarks and leptonsf under the assumption that the matricesm _L andm _R are common to all flavors (up-/down- and quark-/lepton-sectors) and the matricesM _F characterizing the heavy fermion sectors have the form [(unit matrix)+b _f (a democratic matrix)] whereb _f is a flavor parameter. We find that by adjusting the complex parameterb _f, the model can provide thatm _t?m _b while at the same time keepingm _u??m _d without assuming any parameter with hierarchically different values betweenM _U andM _D. The model with three adjustable parameters under the ??maximal?? top-quark-mass enhancement can give reasonable values of five quark-mass ratios and four KM matrix parameters.     

Consequence analysis of blast wave from accidental gas explosions

Recently, consequence analyses of accidental gas explosions are often carried out to assess the risk of chemical plants, hazardous-materials sites and new energy systems. In these consequence analyses, it is indispensable to adequately predict the blast-wave (pressure-wave) intensity from gas deflagrations. Some prediction models already exist; however, most of them are based on the theory for explosives and adjusting parameters are needed for evaluating gas deflagrations. In this study, new prediction methods for gas deflagrations were developed. From theoretical analysis of blast-wave generation by a gas deflagration, an evaluation equation of the blast-wave intensity was derived. As the scale of gas deflagration becomes larger, flame front instability (especially hydrodynamic instability) would be more effective and the flame propagating velocity starts to be accelerated. Therefore, the equation was modified considering the effect of flame instability. The evaluations by this modified equation agreed well with the results of large scale experiments. By this analysis, it was found that not only total energy release but also combustion reaction rate has to be introduced into the prediction of gas deflagrations. Using this concept, a modified scale model to predict the blast-wave intensity was developed by improving the previous scale model introducing the term of combustion reaction rate as burning velocity. Furthermore, scale analysis was performed to develop the new scaling law. The universal relationship between scaled distance and overpressure has been realized by this new scaling law for gas deflagrations. In summary, these results provide new methods for accurate prediction of the blast-wave intensity from gas deflagrations.     

Very fast magic angle spinning (1)H-(14)N 2D solid-state NMR: sub-micro-liter sample data collection in a few minutes

Substantial resolution and sensitivity enhancements of solid-state (1)H detected (14)N HMQC NMR spectra at very fast MAS rates up to 80 kHz, in a 1mm MAS rotor, are presented. Very fast MAS enhances the (1)H transverse relaxation time and efficiently decouples the (1)H-(14)N interactions, both effects leading to resolution enhancement. The micro-coil contributes to the sensitivity increase via strong (14)N rf fields and high sensitivity per unit volume. (1)H-(14)N HMQC 2D spectra of glycine and glycyl-L-alanine at 70 kHz MAS at 11.7 T are observed in a few minutes with a sample volume of 0.8 μL.     

Synthesis of titanium silicalite-1 (TS-1) zeolite with high content of Ti by a dry gel conversion method using amorphous TiO2–SiO2 composite with highly dispersed Ti species

In this study, we have developed a new method to synthesize mesoporous titanium silicalite-1 (TS-1) with a higher content of active titanium in the framework (more than 5%) than that obtained from the conventional hydrothermal synthesis. The new method combines two methods as follows: (1) a sol-gel method in tetrahydrofuran for the synthesis of TiO₂–SiO₂ composite with highly dispersed Ti species and (2) a dry gel conversion method for the crystallization to TS-1. This investigation revealed that the dispersion of Ti in the starting materials was quite important to synthesize mesoporous TS-1 with high content of Ti besides dry conversion method. The obtained mesoporous TS-1 with a high content of titanium showed higher catalytic activity in 1-hexene epoxidation than conventional TS-1. This high activity is likely to originate from the high content of titanium in the framework.     

Synthesis of the Pluramycins 1: Two Designed Anthrones as Enabling Platforms for Flexible Bis‐C‐Glycosylation

Two effective tricyclic platforms are reported for the installation of the two constituent sugars, L ‐vancosamine and D ‐angolosamine, in a regio‐ and stereoselective manner for the synthesis of the pluramycin class of bis‐C‐glycoside antitumor antibiotics. Two complementary protocols are now available that differ in the order in which the two sugar moieties are installed. Sc(OTf)₃ was effective as the Lewis acid.     

Excited‐State Dynamics of Pentacene Derivatives with Stable Radical Substituents

The excited‐state dynamics of pentacene derivatives with stable radical substituents were evaluated in detail through transient absorption measurements. The derivatives showed ultrafast formation of triplet excited state(s) in the pentacene moiety from a photoexcited singlet state through the contributions of enhanced intersystem crossing and singlet fission. Detailed kinetic analyses for the transient absorption data were conducted to quantify the excited‐state characteristics of the derivatives.     

Breaking the Semi‐Quinoid Structure: Spin‐Switching from Strongly Coupled Singlet to Polarized Triplet State

2,7‐TMPNO (4,5,9,10‐tetramethoxypyrene‐2,7‐bis(tert‐butylnitroxide)) was found to exist in semi‐quinoid form with unprecedented strong intramolecular magnetic exchange interaction of 2 J/k_B=1185 K operating over a distance of 10 Å. Structural transformations with the activation energy of ΔE_eq=949 K were observed by varying the temperature, from more quinoid structure at low temperature to more biradicaloid structure at higher temperature. Moreover, this molecule undergoes a transient spin transition from singlet to polarized triplet state upon photoexcitation revealed by TREPR spectroscopy. The spin Hamiltonian parameters were determined to be S=1, g=2.0065, D=?0.0112 cm^?1, and E=?0.0014 cm^?1 by spectral simulation with the hybrid Eigenfield/exact diagonalization method.     

Facile Synthesis of 3‐Hydroxyglutamic Acids via Cyanation of Chiral N‐Acyliminium Cation Derived From (S)‐Malic Acid

Facile synthesis of 3‐hydroxyglutamic acids via cyanation of an N‐acyliminium intermediate derived from (S)‐malic acid is described. The chiral cyclic imide derived from (S)‐malic acid was converted to an acetoxylactam by reduction with sodium borohydride followed by acetylation. The obtained acetoxylactam was treated with trimethylsilyl cyanide in the presence of boron trifluoride etherate to give the corresponding cyanolactam in high yield, even though the diastereoselectivity of the cyanation reaction was moderate. The diastereomers of the cyanolactam were chromatographically separable and were independently converted to (2R,3S)‐ and (2S,3S)‐3‐hydroxyglutamic acids.