Free Convective Nonaligned Non-Newtonian Flow with Non-linear Thermal Radiation

The present study explores the free convective oblique Casson fluid over a stretching surface with non-linear thermal radiation effects. The governing physical problem is modelled and transformed into a set of coupled non-linear ordinary differential equations by suitable similarity transformation, which are solved numerically with the help of shooting method keeping the convergence control of 10^-5 in computations. Influence of pertinent physical parameters on normal, tangential velocity profiles and temperature are expressed through graphs. Physical quantities of interest such as skin friction coefficients and local heat flux are investigated numerically.     

Synthesis of nitrogen- and oxygen-containing macrocycles--derivatives of lithocholic Acid

Palladium-catalyzed amination of 3,24-bis(3-bromophenoxy)cholane (4) with various polyamines and polyoxadiamines 5 taken in 1:1 ratio was used for the synthesis of the macrocycles 6, which contain steroidal and polyamine moieties and were obtained in 38-65 % yields. The same reaction with excess polyamine (2.2-3 equiv) provided bis(polyamino) derivatives of 3,24-diphenoxycholane 7 in excellent yields, whereas the diarylation of polyamines with two equivalents of 3,24-bis(3-bromophenoxy)cholane afforded their bis(steroidal) derivatives 8. Compounds 7 and 8 were employed in the syntheses of cyclodimers 9, which possess two steroidal and two polyamine fragments; the efficiency of two methods was compared.     

Hydro- and silylcyanation of cholic acid derivatives. Synthesis of novel pincer ligands based on litocholic acid

Reactions of 3-oxo derivatives of cholic acid esters with acetone cyanohydrin and trimethylsilyl cyanide lead to exclusive or predominant formation of the corresponding 3-cyano-3-hydroxy and 3-cyano-3-trimethylsiloxy derivatives with axial orientation of the cyano group. Reduction of the cyano group in the addition products gives 3-aminomethyl derivatives which can be used to obtain pincer ligands containing two cholane fragments.     

Pd-catalyzed alkylation of halogen-substituted steroids with organozinc compounds

A general procedure has been developed for the introduction of hydrophobic alkyl groups into positions 6, 3, and 17 of steroid molecules via palladium-catalyzed Negishi reaction of halogen-substituted steroids with benzyl- and alkylzinc halides.     

Cascade Transformations of [1,2,3]Triazolo[1,5-a]pyridines as Convenient Precursors of Diazo Compounds and Metal Carbenes

Russian Journal of Organic Chemistry - The review is devoted to the use of [1,2,3]triazolo[1,5-a]pyridines as precursors of tautomeric 2-(diazomethyl)pyridines. This methodology represents a...     

Synthesis of silyl,germyl, and phosphino-substituted acylketenes from pivaloylethoxyacetylene

The reaction of pivaloylethoxyacetylene with silicon halides, which has been found to occur as a 1,4-addition, leads to allenic ethers, which readily eliminate ethyl halides and are converted to previously unknown types of ketenes—stable element-substituted acylketenes. Germanium-substituted acylketenes are also formed; however, clear evidence of 1,4-addition of germanium halides was not obtained. In the reaction between Ph₂PCl and pivaloylethoxyacetylene, phosphorus (III) substituted acylketenes initially formed underwent rapid [3 + 3] cyclodimerization.