High-efficiency arrays of any desired optical beams using modified grating-based elements

High efficiency grating-based diffractive elements were previously proposed in order to generate desired arrays of various optical beams. The elements enable us to generate a diversity of arrays of optical beams in desired shapes, so that the arrays produced by the method are homogeneous, uniform and lacking of unwanted higher diffraction orders. In this technique a modulated grating is used to restructure Fresnel zone plate or zone plate-based elements to get modified grating-based elements. To examine the method, a variety of rectangular arrays of optical spots and annular beams are created by the ordinary and modified elements. It is shown that the arrays generated by the modified elements are much more uniform than the same arrays produced by the ordinary ones. In addition to the uniformity of the arrays, the unwanted higher diffraction orders are also totally eliminated. This article exploits simulation and experimental studies in order to demonstrate the functionality of the proposed technique as a multi functional high-efficiency beam shaping.     

α,β-Unsaturated ketones based on allobetulone

Crotonization of allobetulone with aromatic and heteroaromatic aldehydes gave a number of new α,β-unsaturated ketones of the lupane series, and their steric structure was determined by X-ray analysis of (E)-4-[(3-oxoallobetulan-2-ylidene)methyl]benzonitrile as an example.     

Diastereoselective synthesis of β-substituted α-hydroxyphosphinates through hydrophosphinylation of α-heteroatom-substituted aldehydes

The diastereoselective synthesis of β-substituted α-hydroxyphosphinates was achieved by hydrophosphinylation of α-oxy aldehydes and α-amino aldehydes with ethyl allylphosphinate catalyzed by lithium phenoxide.     

The first separation and stereochemical determination of bis(α-hydroxyalkyl) phosphinic acids diastereoisomers

A separation of bis(α-hydroxyalkyl) phosphinic acid diastereoisomers is described. A novel method for the determination stereochemistry of bis(α-hydroxyalkyl) phosphinic acid diastereoisomers has been developed. The stereochemistry of one diastereoisomer was confirmed after converting to the corresponding methyl ester using trimethyl orthoformate.     

Osmium tetroxide-promoted catalytic oxidative cleavage of olefins: an organometallic ozonolysis

A mild, organometallic alternative to ozonolysis utilizing oxone and OsO(4) is presented. This is a direct oxidation of olefins via the carbon-carbon cleavage of an osmate ester by the action of oxone. Twenty-four different olefins were converted to their corresponding ketones or carboxylic acids in high yields (>80%). Free alcohols, acetate- and benzyl-protected alcohols, and 1,2-diols were stable under these conditions. This method should be applicable for traditional organic synthesis.     

Prompt determination of absolute configuration for epoxy alcohols via exciton chirality protocol

A microscale protocol for determination of absolute configurations of 2,3-epoxy alcohols is described. 2,3-Disubstituted (cis and trans), 2,2-disubstituted, 2,2,3-trisubstituted, and 2,3,3-trisubstituted epoxy alcohols rendered prominent ECCD signals upon complexing with a Lewis acidic porphyrin tweezer and consequently provide straightforward assignment of chirality for epoxy alcohols. This method proved to be rapid, simple, sensitive, and reliable for the class of molecules listed above.