Alkylamines‐intercalated α‐zirconium phosphate as latent thermal anionic initiators

The reaction of glycidyl phenyl ether (GPE) with 1‐aminoalkanes‐intercalated α‐zirconium phosphate (α‐ZrP·1‐aminoalkane): 1‐aminoalkanes 1‐aminopropane (α‐ZrP·Pr), 1‐aminobutane (α‐ZrP·Bu), 1‐aminooctane (α‐ZrP·Oct), and 1‐aminohexadecane (α‐ZrP·Hed) was carried out at varying temperatures for 1 h periods. Reaction progress was not observed until the reactants were heated to 80 °C or above. On increasing the temperature, the conversion factors increased such that, at 140 °C, conversions of 62% (α‐ZrP·Pr), 60% (α‐ZrP·Bu), 67% (α‐ZrP·Oct), and 64% (α‐ZrP·Hed) were obtained. The thermal stabilities as latent initiators were tested: GPEs reacted with α‐ZrP·Pr, α‐ZrP·Bu, and α‐ZrP·Oct at 40 °C for 360 h achieved conversions of 83, 55, and 59%, respectively. In contrast, the reaction in the presence of α‐ZrP·Hed did not proceed at 40 °C. The order of the thermal stability of GPE in the presence of α‐ZrP·1‐aminoalkane intercalation compounds was: α‐ZrP·Hed > α‐ZrP·Bu ≈ α‐ZrP·Oct > α‐ZrP·Pr. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1854–1861     

Synthesis of glycol diesters through the depolymerization of polyethylene glycols with carboxylic acids using a proton-exchanged montmorillonite catalyst

A convenient and sustainable method for the synthesis of glycol diesters was developed through the depolymerization of polyethylene glycols (PEGs) with carboxylic acids using proton-exchanged montmorillonite as an efficient solid acid catalyst. Several functionalized glycol diesters were obtained in good yields from PEGs and readily available carboxylic acids. Upon reaction completion, the catalyst could be easily separated by filtration and reused with its activity remaining unchanged.     

Synthesis and reaction of 5-amino-3-trifluoromethylisoxazole and -pyrazole-4-carboxylic acids

5-Amino-3-trifluoromethylisoxazole- and -pyrazole-4-carboxylic acids were prepared by the reactions ot trifluoroacetonitrile oxide or -imines with cyanoacetic acid derivatives, respectively. The behavior of thus obtained aminoazole-4-carboxylic acids toward some electrophiles was examined. In acylation with acyl chlorides, the aminoisoxazole-4-carboxylate 2a was diacylated to give the (diacylamino)isoxazole-4-carboxylate 7 , whereas the analogous aminopyrazole 5a produced the cyclized pyrazolooxazinone 13 . Moreover, carbamoylation of 2a with isocyanates gave the trifluoromethylisoxazolouracils 10 .     

Cycloadditions of N-Aryl-C-(trifluoromethyl)nitrilimines with dimethyl fumarate and maleate

The cycloadditions of N-aryl-C-(trifluoromethyi)nitrilimines 1 , generated in situ from various precursors, with dimethyl fumarate and maleate are described. N-Aryltrifluoroacetohydrazonoyl bromides 2 reacted with fumarate in the presence of triethylamine to give the trans-4,5-dimethoxycarbonylpyrazolines 4 whereas the reactions with maleate afforded the 4,5 -dimethoxycarbonylpyrazoles 5 as well as 4. In the reactions with the chloride 6 under the more drastic conditions, both fumarate and maleate gave the pyrazole 5a. From thermolysis of the oxadiazaphosphole 8 , the trans-pyrazoline 4a was formed in both cases of fumarate and maleate. The preparation of the cis-pyrazoline 9 was attempted from 8 and maleic anhydride but 9 was found to be so unstable as to be epimerized under the mild conditions.     

Quinolone analogues 8 [1‐6]. Synthesis of 3‐aminopyridazino‐[3,4‐b]quinoxalin‐4(lH)‐one

The 3‐amino‐1‐methylpyridazino[3,4‐b]quinoxalin‐4(1H)‐one 6 and N‐(1,4‐dihydro‐1‐methyl‐4‐oxopyridazino[3,4‐b]quinoxalin‐3‐yl)carbamates 17a,b were synthesized from the 1,4‐dihydro‐1‐methyl‐4‐oxopyridazino[3,4‐b]quinoxa‐line‐3‐carboxylate 1b via the 1,5‐dihydro‐4‐hydroxy‐1‐methylpyridazino[3,4‐b]quinoxaline‐3‐carbohydrazide 13b and then 1,4‐dihydro‐1‐methyl‐4‐oxopyridazino[3,4‐b]quinoxaline‐3‐carboxazide 8 . Heating of compound 13b and arylalde‐hydes afforded the 1,4‐dihydro‐1‐methyl‐4‐oxopyridazino[3,4‐b]quinoxaline‐3‐carbo(2‐arylmethylene)hydrazides 14a‐d.     

RA‐dimer B,a New Dimeric RA‐series Cyclopeptide Incorporating Two Different Types of Cycloisodityrosine Units,from Rubia cordifolia L.

RA‐dimer B, a new cytotoxic RA‐series peptide, was isolated from the roots of Rubia cordifolia L. Its structure was elucidated on the basis of spectroscopic analysis to be a dimeric cyclopeptide composed of deoxybouvardin and allo‐RA‐V. Those two cyclopeptide units are connected by an ether linkage between the phenolic oxygen atom of deoxybouvardin and the ?a carbon atom of Tyr‐6 of allo‐RA‐V. RA‐dimer B was synthesized by the coupling reaction of deoxybouvardin with the boronic acid derivative of allo‐RA‐V, and subsequent deprotection, confirming the relative stereochemistry and establishing the absolute configuration of this peptide. RA‐dimer B showed cytotoxic activity against human promyelocytic leukaemia HL‐60, human colonic carcinoma HCT‐116, and human renal cell carcinoma ACHN cells with IC₅₀ values of 0.59, 0.54, and 0.74 μm , respectively.     

Metamagnetic quantum criticality revealed by 17O-NMR in the itinerant metamagnet Sr3Ru2O7

We have investigated the spin dynamics using 17O-NMR in the bilayered perovskite Sr3Ru2O7, which sits close to a metamagnetic quantum critical point. The nuclear spin-lattice relaxation rate divided by temperature 1/T1T is enhanced on approaching the metamagnetic critical field of approximately 7.9 T, and at the critical field 1/T1T continues to increase and does not show Fermi-liquid behavior down to 0.3 K. The temperature dependence of T1T in this region suggests the critical temperature Theta to be approximately 0 K, which is strong evidence that the spin dynamics possesses a quantum critical character. Comparison between uniform susceptibility and 1/T1T reveals that antiferromagnetic fluctuations instead of two-dimensional ferromagnetic fluctuations dominate the spin fluctuation spectrum at the critical field, which is unexpected for itinerant metamagnetism.