Optically active ether irradiation

Under irradiation in diethyl ether, the dextrorotary enantiomer of 3,6-hexanooxepin-4-carb-oxylic acid rearranges to the oxabicyclo[3.2.0]heptadiene system with retention of the optical activity.36... 

Interestingly, the alkene to allene conversion can be carried out directly without isolation of the intermediate dihalocyclopropane. This process involves the treatment of the alkene with 1 equiv. of carbon tetrabromide and 2 equiv. of methyllithium in ether at -65 °C.163 Ultrasonic irradiation facilitates the formation of cyclopropylidenes, and therefore the allenes, from dihalocyclopropanes under the influence of Li, Na or Mg.1 The reactions are usually complete in 5-15 min. A report165 on the use of n-butyllithium complexed with the chiral tertiary amine (-)-sparteine, leading to optically active allenes, seems to be of questionable value. 

More detailed kinetic information about the motions and reactions of the alkyl/aryloxy radical pairs can be obtained if the alkyl carbon atom making an ether bond is chiral and the alkyl aryl ether is optically active. Because the radical centers of the alkyl fragments derived from irradiation of such ethers are either planar or invert very rapidly, they exist initially with their aryloxy partners as prochiral pairs. Their ability to retain the memory of the chirality of their parent ethers and impart it to the rearrangement products depends on the ratio between the in-cage rates of radical tumbling and radical pair combination. 

The optically active endo-bicyclo-octene aldehyde (800), prepared by standard reactions from (798) via (799), is converted on u.v. irradiation into the cyclic ether (801) which can be reductively cleaved regiospeciGcally with LiAlH4 in JV-methylmorpholine to the alcohol (802). Net reduction of the alcohol (802) was achieved by the standard sequence (802)- (803)- (804). The final hydrocarbon product, (+)-twistbrendane (804), is in effect a nortwistane chiroptical data confirms (804) to be the enantiomer of the previously prepared (—)-twistbrendane. ... 

Upon photolysis, tropolone alkyl ether 7 undergoes intramolecular 4n elect-rocyclization to afford chiral bicyclo[3.2.0]heptadienone 8, which rearranges to compound 9 upon prolonged irradiation (Scheme 6). The photocyclization of CD-complexed tropolone methyl ether 7a was hrst studied by Takeshita and coworkers [46]. They found that the formation of CD complex improves the yield of the optically active product 8a, but the ee value was not quantitatively determined. 

SnC>2 nanoparticles have been successfully synthesized by chemical co-precipitation method using ethanol, acetone, tetrahydrofuran (THF) and ether as solvents. X-ray Diffraction (XRD), Field Emission Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) have been used to study the crystallographic and morphological properties of synthesized SnC>2 nanoparticles, while their optical properties have been studied by UV-Visible absorption spectroscopy. UV-Vis absorption spectra shows a weak quantum confinement in all the synthesized SnCL samples. The photo-catalytic activity of as-synthesized SnC>2 nanoparticles under UV irradiation has been evaluated using Methylene Blue (MB) dye as a test contaminant in water. The results showed that solvents played a key role to control the morphology and photo-catalytic activity of SnCE nanoparticles. 

---