Nucleophilic acylation of α-haloketones with aldehydes: an umpolung strategy for the synthesis of 1,3-diketones

The first example of N-heterocyclic carbene (NHC)-promoted intermolecular acylation of α-haloketones with aldehydes and α,β-unsaturated aldehydes (enals) is reported. The protocol involves carbonyl umpolung reactivity of aldehydes and enals in which the carbonyl carbon attacks nucleophilically on electrophilic terminal of α-haloketones to afford 1,3-diketones and α,β-unsaturated 1,3-diketones, respectively. Short reaction time, ambient temperature, operational simplicity, and high yields are the salient features of the present procedure.     

BF3·OEt2-catalyzed tandem Prins Friedel-Crafts reaction: a novel synthesis of sugar fused diarylhexahydro-2H-furo[3,2-b]pyrans

d-Glucose based homoallylic alcohol reacts smoothly with various aldehydes in the presence of arenes and a catalytic amount of BF₃·OEt₂ under mild conditions to afford a novel series of 5,7-diaryl-hexahydro-2H-furo[3,2-b]pyrans in good yields with high cis-selectivity.     

Reductive Cleavage of Phthalides with Iodotrimethylsilane

A convenient reductive cleavage of 3-arylphthalides 1 into corresponding 2-benzylbenzoic acids and 2-(2-thienylmethyl)benzoic acid 2 by using iodotrimethyisilane is described.     

Total Synthesis of Aculeatins A and B from L‐Malic Acid

An efficient total synthesis of the cytotoxic spiroketal natural products aculeatin A and B is described. The synthesis of the 1,3,5‐triol moiety with appropriate configuration was accomplished from the commercially available L ‐malic acid. The key steps in this synthesis are the Barbier allylation, LiAlH₄/LiI‐mediated syn‐stereoselective 1,3‐asymmetric reduction, and phenyliodine bis(trifluoroacetate) (=[bis(trifluoroacetoxy)iodo]benzene; PIFA) mediated oxidative spirocyclization.     

Fabrication of double-aperture hololens imaging system: application to mechanics

Duffy suggested the use of double-aperture imaging system for the measurement of in-plane displacement component. In this arrangement, twin apertures are placed symmetrically over the imaging lens. This imaging system is used in speckle metrology to measure component of displacement parallel to the line joining the two apertures. The imaging lens used in such configuration need not be diffraction limited over the entire lens aperture, but only over the two small areas encompassed by the two apertures. In present work, compact holographic lenses have been used to generate the two apertures of Duffy's double-aperture interferometer. This imaging system has been used in speckle metrology to measure crack mouth opening displacement (CMOD) in an aluminium beam specimen having central edge crack subjected to three point bending. Experimental results are in good agreement with theoretical predictions. Present experimental investigation reveals that compact holographic lenses can be used advantageously to generate apertures of double-aperture speckle interferometer for its use in the measurement of in-plane displacement component.     

Phonon spectrum and mean-square-atomic displacements of ZrC

The lattice dynamics of ZrC has been studied on the basis of extended deformation dipole model (EDDM). The experimental data agree with the data obtained for the dispersion curves. The modes has also been used to calculate mean-square-atomic displacements.     

Study of 18 40 Ar ion tracks in cellulose nitrate

Sample of cellulose nitrate (Russian) is exposed to ₁₈ ⁴⁰ Ar ions. The bulk etch rate has been studied at different etching temperatures and the activation energy for bulk etch rate has been calculated. The etched track lengths are measured for different etching times. The energy loss rate and range of ₁₈ ⁴⁰ Ar ions in CN(R) is also calculated. The critical threshold value for etchable track in CN(R) is determined by comparing the theoretical and experimental values of track length. The response curve of CN(R) is also presented.     

A search for superheavy nuclei tracks in extraterrestrial olivine crystals

A study is made for the search of superheavy nuclei in Marjalahti, Eagle Station and in other pallasite olivines. The olivine crystals are calibrated for heavy ion track lengths by using heavy ion beams from cyclotrons. The calibration for ultra heavy ions which are presently not available with sufficient energy to produce volume tracks in olivine crystals, is based on Katz and Kobetich model of track formation. The length spectrum of volume tracks, revealed by puncturing them with focussed Nd-glass laser beam, is measured and the abundances of different nuclei groups are calculated. Partial annealing has been used at 430°C for 32 hr which eliminates the interfering tracks due to nuclei of atomic numberS ≤ 50. During the scanning 4 cm³ olivine crystals, about 360 long tracks of uranium group as well as two very long tracks have been found. If these tracks belong to superheavy nuclei, the relative abundance of super heavies is found to be 6 × 10⁻¹¹ in galactic cosmic rays.