[Hydroxy(tosyloxy)iodo]benzene: A Tosyloxylating Agent with Selectivity for Ketones in the Reactions with Benzalacetones

The treatment of enolizable ketones containing a conjugated double bond, namely benzalacetones with [hydroxy(tosyloxy)iodo]benzene, leads to regioselective tosyloxylation, thereby giving new compounds (α-tosyloxybenzalacetones).     

One-Pot Synthesis of Biologically Important Spiro-2-amino-4H-pyrans,Spiroacenaphthylenes, and Spirooxindoles Using DBU as a Green and Recyclable Catalyst in Aqueous Medium

We have reported DBU-catalyzed one-pot synthesis of biologically and pharmacologically important spiropyrans from condensation of malononitrile/ethyl cyanoacetate, 1,3-dicarbonyl compounds, and ninhydrin/acenaphthequinone/istain in good yields. This new protocol employing DBU, which is a green, recyclable, and inexpensive catalyst, offers advantages such as mild reaction conditions, short reaction times, and easy isolation of products. The structures have been confirmed by x-ray analysis.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Generalised strip-saturation zone models for piezoelectric strip weakened by non-centric semi-permeable crack

Meccanica - In this paper, we have proposed generalised strip-saturation zone models for non-centric semi-permeable straight hairline crack weakening a piezoelectric strip. Strip-saturation zone...     

2-Phosphaindolizines

Abstract

An overview of 2-phosphaindolizines, i.e. 1,3-azaphospholo[1,5-a]pyridines along with their 1-aza-, 3-aza- and 1,3-diaza analogues has been presented. It includes their methods of syntheses, characterization and reactions. Under reactions, electrophilic substitutions, N-alkylation, Diels-Alder (DA) reactions with the >C=P- functionality in the absence of the catalyst and also in the presence of the catalyst, other 1,2-additions across the >C=P- functionality, cheletropic cycloaddition of tetrachloro-o-benzoquinone (TCQ) with the phosphorus atom and co-ordination with the metal pentacarbonyls and other derivatives have been described.     

Glycolipids that elicit IFN-γ-biased responses from natural killer T cells

Natural killer T (NKT) cells recognize glycolipids presented by CD1d. The first antigen described, α-galactosyl ceramide (αGalCer), is a potential anticancer agent whose activity depends upon IFN-γ secretion. We report two analogs of αGalCer based on a naturally occurring glycosphingolipid, plakoside A. These compounds induce enhanced IFN-γ that correlates with detergent-resistant binding to CD1d and an increased stability of the lipid-CD1d complexes on antigen-presenting cells. Structural analysis on one of the analogs indicates that it is more deeply bound inside the CD1d groove, suggesting tighter lipid-CD1d interactions. To our knowledge, this is the first example in which structural information provides an explanation for the increased lipid-CD1d stability, likely responsible for the Th1 bias. We provide insights into the mechanism of IFN-γ-inducing compounds, and because our compounds activate human NKT cells, they could have therapeutic utility.     

Halide coordination of perhalocyclohexasilane Si6X12 (X=Cl or Br)

The addition of halide anions (X' = Cl(-), Br(-), or I(-)) to perhalocyclohexasilane Si(6)X(12) (X = Cl or Br) led to the formation of complexes comprising [Si(6)X(12)X'(2)](2-) dianions. An upfield shift in the (29)Si NMR spectra was noted upon coordination, and structural determination by X-ray crystallography showed that the dianions adopt an "inverse sandwich" structure where the six cyclic silicon atoms form a planar hexagon with the two halide anions X' located on the 6-fold axis equally disposed above and below the plane of the Si(6) ring. Additionally, these apical X' atoms are within the van der Waals bonding distance to the silicon ring atoms, indicating a strong interaction between X' and silicon atoms. These results detail crystallographic variations within the halogen series providing further insight into the nature of the Lewis acid sites above and below the Si(6)X(12) ring, where interactions with hard Lewis bases such as halide anions are observed. Interestingly, the stereochemistry of the silicon atoms in [Si(6)X(12)X'(2)](2-) is not affected much by the size or electronegativity of the halogen atoms.     

Highly adequate oxidative esterification of α-carbonyl aldehydes with alkyl halides in TBAI/TBHP mediated system

An efficient and viable synthesis of α-ketoesters from alkyl halides and α-carbonyl aldehydes has been reported under metal-free conditions. The present method involves oxidative esterification of α-carbonyl aldehydes with alkyl halide using TBAI as a promoter and TBHP as an oxidant to form α-ketoesters in good to excellent yields with versatile structural diversity. Use of commercially accessible and inexpensive substrates, broad substrate scope and good functional group tolerance are the key features of this protocol.