An Yb(OTf)3‐catalyzed,convergent synthesis of new pyranyl‐ and chromenyl‐substituted quinolines through an eco‐friendly approach

A one‐pot, multicomponent, convergent microwave synthesis of some new pyranyl‐ and chromenyl‐substituted quinolines has been reported. Twenty compounds were prepared by the reaction of 2‐methoxy‐3‐formyl quinoline ( 1a‐d ), malononitrile ( 2 ), and kojic acid ( 4a‐d )/1,3‐cyclohexadione or dimedone ( 6a ‐ h )/α‐ or β‐naphthol ( 8a ‐ d , 8e ‐ h ). The structures were confirmed by infrared (IR), ¹H nuclear magnetic resonance (NMR), ¹³C NMR, mass, and single‐crystal X‐ray analyses. On comparison with the use of conventional Lewis acid catalysts and various metal triflates under microwave conditions, the latter contributed to good yields, in specific use of the recyclable Yb(OTf)₃ catalyst attributed to high yields of the desired product. The protocol reported herein is solvent free, cost effective, and eco‐friendly.     

Elementary abelian 2-group actions on flag manifolds and applications

Let denote the unoriented cobordism ring. Let and let denote the equivariant cobordism ring of smooth manifolds with smooth -actions having finite stationary points. In this paper we show that the unoriented cobordism class of the (real) flag manifold is in the subalgebra generated by , where , and . We obtain sufficient conditions for indecomposability of an element in . We also obtain a sufficient condition for algebraic independence of any set of elements in . Using our criteria, we construct many indecomposable elements in the kernel of the forgetful map in dimensions , for , and show that they generate a polynomial subalgebra of .

     

Conformations of dimethylhydrogen phosphonate (DMHP): a matrix isolation infrared and ab initio study

The infrared spectra of dimethylhydrogen phosphonate (DMHP) isolated in nitrogen, argon and krypton matrices using an effusive source at 298 and 373 K have been recorded. Experiments were also performed using a supersonic jet source to look for conformational cooling in the expansion process. As a result of these experiments, infrared spectral characteristics of the ground and higher energy conformers of the DMHP have been identified for the first time. The structures of DMHP were optimized at the hybrid B3LYP and Hartree fock (HF) levels of theory using the 6-31++G** basis sets. Computationally, four minima were obtained corresponding to DMHP conformers with G (+/-)G (-/+), G (-)G (-), TG (+) and TG (-) structures in the order of increasing energy. Frequency calculations were done to confirm that the structures were indeed minima on the potential energy surface (PES). The computed frequencies corroborated well with the experimental matrix isolation infrared frequencies leading to definite assignments of the infrared features of DMHP, for the G (+/-)G (-/+) and TG (+) conformers. At B3LYP/6-31++G** level, the energy difference between the G (+/-)G (-/+) and G (-)G (-) conformer was 1.53 kcal/mol, and that between G (+/-)G (-/+) and TG (+), G (+/-)G (-/+) and TG (-) were 1.65 and 1.95 kcal/mol. Transition-state calculations were also carried out at B3LYP/6-31++G** level connecting the G (+/-)G (-/+) to G (-)G (-), TG (+) and TG (-) conformers. Computations indicated that the conformer interconversion between G (-)G (-) --> G (+/-)G (-/+) is barrierless, whereas the barriers for TG (+) --> G (+/-)G (-/+) and TG (-) --> G (+/-)G (-/+) are 1.47 and 0.88 kcal/mol, respectively.     

Acid-base, electron donating and catalytic properties of sulfated zirconia

The electron donating properties of sulfated zirconia were studied from the adsorption of electron acceptors of various electron affinity. The surface acidity and basicity of the oxides have also been determined by titration method using a set of Hammett indicators. The data have been correlated with the catalytic activity of the oxide towards esterification of acetic acid usingn-butanol, reduction of cyclohexanol in 2-propanol and oxidation of cyclohexanol with benzophenone.     

Photopolymers: Synthesis and Characterization of Poly(3‐methacryloyloxystyryl‐2‐naphthyl ketone)

3‐Methacryloyloxystyryl‐2‐naphthyl ketone containing a photosensitive α,β‐unsaturated ketone moiety was synthesized and polymerized in methyl ethyl ketone using benzoyl peroxide as the initiator. The thermally stable polymer was characterized by means of UV, IR and NMR spectroscopy. The molecular weight data as obtained from gel permeation chromatography suggests a high tendency for chain termination by disproportionation. The photosensitivity of the polymer in the presence and absence of photosensitizers and the effect of solvent on the rate of photocrosslinking (see Figure) was also investigated.     

Wahl’s conjecture holds in odd characteristics for symplectic and orthogonal Grassmannians

It is shown that the proof by Mehta and Parameswaran of Wahl’s conjecture for Grassmannians in positive odd characteristics also works for symplectic and orthogonal Grassmannians.      

A regioselective multicomponent protocol for the synthesis of novel bioactive 4-hydroxyquinolin-2(1H)-one grafted monospiropyrrolidine and thiapyrrolizidine hybrids

An expedient route toward the synthesis of 4-hydroxyquinolone grafted spiropyrrolidines or pyrrolizidines has been accomplished through 1,3-dipolar cycloaddition reaction of various azomethine ylides derived from isatin or acenaphthalene and sarcosine with 4-hydroxyquinolone derivatives as dipolarophile. The regio and stereo chemical outcome of the cycloaddition reaction is ascertained by X-ray crystallographic studies and spectroscopic techniques of the cycloadducts. Furthermore, cytotoxicity evaluation of selected compounds showed significant inhibition of cell proliferation against cervical as well as colon cancer cell lines.     

Reporting of quantitative oxygen mapping in EPR imaging

Oxygen maps derived from electron paramagnetic resonance spectral-spatial imaging (EPRI) are based upon the relaxivity of molecular oxygen with paramagnetic spin probes. This technique can be combined with MRI to facilitate mapping of pO(2) values in specific anatomic locations with high precision. The co-registration procedure, which matches the physical and digital dimensions of EPR and MR images, may present the pO(2) map at the higher MRI resolution, exaggerating the spatial resolution of oxygen, making it difficult to precisely distinguish hypoxic regions from normoxic regions. The latter distinction is critical in monitoring the treatment of cancer by radiation and chemotherapy, since it is well-established that hypoxic regions are three or four times more resistant to treatment compared to normoxic regions. The aim of this article is to describe pO(2) maps based on the intrinsic resolution of EPRI. A spectral parameter that affects the intrinsic spatial resolution of EPRI is the full width at half maximum (FWHM) height of the gradient-free EPR absorption line in frequency-encoded imaging. In single point imaging too, the transverse relaxation times (T(2)(?)) limit the resolution since the signal decays by exp(-t(p)/T(2)(?)) where the delay time after excitation pulse, t(p), is related to the resolution. Although the spin densities of two point objects may be resolved at this separation, it is inadequate to evaluate quantitative changes of pO(2) levels since the linewidths are proportionately affected by pO(2). A spatial separation of at least twice this resolution is necessary to correctly identify a change in pO(2) level. In addition, the pO(2) values are blurred by uncertainties arising from spectral dimensions. Blurring due to noise and low resolution modulates the pO(2) levels at the boundaries of hypoxic and normoxic regions resulting in higher apparent pO(2) levels in hypoxic regions. Therefore, specification of intrinsic resolution and pO(2) uncertainties are necessary to interpret digitally processed pO(2) illustrations.