Ion Recognition Approach to Volume Reduction of Alkaline Tank Waste by Separation of Sodium Salts

The purpose of this research involving collaboration between Oak Ridge National Laboratory (ORNL) and Pacific Northwest National Laboratory (PNNL) is to explore new approaches to the separation of sodium hydroxide, sodium nitrate, and other sodium salts from high-level alkaline tank waste. The principal potential benefit is a major reduction in disposed waste volume, obviating the building of expensive new waste tanks and reducing the costs of vitrification. Principles of ion recognition are being researched toward discovery of liquid-liquid extraction systems that selectively separate sodium hydroxide and sodium nitrate from other waste components. The successful concept of pseudo hydroxide extraction using fluorinated alcohols and phenols is being developed at ORNL and PNNL toward a greater understanding of the controlling equilibria, role of solvation, and of synergistic effects involving crown ethers. Synthesis efforts are being directed toward enhanced sodium binding by crown ethers, both neutral and proton-ionizable. Studies with real tank waste at PNNL will provide feedback toward solvent compositions that have promising properties

A practical and facile approach towards indole alkaloids: (-)-mitralactonine

An efficient approach to (-)-mitralactonine using Pictet-Spengler cyclisation with a highly functionalised masked aldehyde is described. Sharpless asymmetric dihydroxylation (SAD) is ­utilised to introduce chirality in the key substrate

Electrospray Ionization Mass Spectrometric Study Of The Metal Cation Complexation Capabilities Of A Novel, Doubly Cage-Annulated Molecular Box

An unusual molecular box, 4, obtained as a mixture of diastereoisomeric, doubly cage-annulated host molecules, i.e., 4a and 4b, has been prepared. The metal cation complexation properties of the mixture of 4a and 4b thereby obtained have been assessed, with comparison to another bis crown 2, via application of electrospray ionization mass spectrometric (ESI-MS) methods. Both host systems 2 and 4 bind selectively to Li+ and Na+, thereby demonstrating preference over the other larger alkali metals. Addition of Ag+ to the solutions containing alkali metals does not result in substantial Ag+ complexation. Analysis of a solution containing only transition metal, not alkali metal, cations indicates that 4 forms complexes with Zn+ and Ag+ along with substantial complexation of Na+ from residual sodium present in the solvents.Chemistr

Total Synthesis of 7′-Desmethylkealiiquinone

The total synthesis of an analogue of the marine alkaloid kealiiquinone has been completed through application of an intramolecular Diels–Alder reaction of an imidazole-containing enyne. Oxidative aromatization of the lactone adduct and <i>N</i>-methylation facilitates C2-oxidation via the imidazolium salt. Conversion of the lactone to the phthalaldehyde derivative and then to the dihydroxybenzoquinone was achieved via a reaction with glyoxal in the presence of KCN. Esterification of the vinylogous diacid and deprotection provided 7′-desmethylkealiiquinone

Total Synthesis of 7′-Des­methyl­keali­iquinone, 4′-Des­methoxy­keali­iquinone, and 2‑Deoxy­keali­iquinone

Synthetic approaches to the imidazo­naphtho­quinone core of kealiiquinone and related <i>Leucetta</i>-derived alkaloids are described. The polysubstituted benzimidazole framework can be constructed through intramolecular Diels–Alder reactions of propiolate-derived enynes followed by oxidation. Adjustment of the oxidation state of the thus formed lactone allows introduction of the 2,3-dihydroxy­benzo­quinone moiety through a presumed benzoin-like condensation between a phthaldehyde derivative and a masked glyoxal equivalent catalyzed by a cyanide ion. Oxidation of the C2-position can be accomplished through application of an operationally simple treatment of an imidazolium salt with bleach, thus producing the corresponding 2-imidazolone. Debenzylation of a late stage intermediate en route to kealiiquinone was compromised by concomitant <i>O</i>-demethylation upon treatment with triflic acid resulting in the formation of non-natural 7′-des­methyl­keali­iquinone. Other endgame strategies were evaluated; however, these efforts did not lead to completion of a synthesis of kealiiquinone but did provide access to other closely related analogues

Enantioselective synthesis of L-CCG-I

Introduction of natural menthol as the chiral auxiliary in a ç-Br-R,â-unsaturated ester leads to enantioselective generation of three chiral centers in a single step on reaction with a glycine anion equivalent to provide L-CCG-I in 94% ee

Total Synthesis of 7′-Des­methyl­keali­iquinone, 4′-Des­methoxy­keali­iquinone, and 2‑Deoxy­keali­iquinone

Synthetic approaches to the imidazo­naphtho­quinone core of kealiiquinone and related <i>Leucetta</i>-derived alkaloids are described. The polysubstituted benzimidazole framework can be constructed through intramolecular Diels–Alder reactions of propiolate-derived enynes followed by oxidation. Adjustment of the oxidation state of the thus formed lactone allows introduction of the 2,3-dihydroxy­benzo­quinone moiety through a presumed benzoin-like condensation between a phthaldehyde derivative and a masked glyoxal equivalent catalyzed by a cyanide ion. Oxidation of the C2-position can be accomplished through application of an operationally simple treatment of an imidazolium salt with bleach, thus producing the corresponding 2-imidazolone. Debenzylation of a late stage intermediate en route to kealiiquinone was compromised by concomitant <i>O</i>-demethylation upon treatment with triflic acid resulting in the formation of non-natural 7′-des­methyl­keali­iquinone. Other endgame strategies were evaluated; however, these efforts did not lead to completion of a synthesis of kealiiquinone but did provide access to other closely related analogues

Studies toward Total Synthesis of Divergolides C and D

A facile synthesis of the western segment of divergolides C and D has been developed. Exploratory studies with two disconnections, i.e., <i>C4–C5 </i>vs<i> C5–C6</i>, for elaboration of the ansa bridge to the sterically demanding hexasubstituted naphthalenic aromatic core using a chiral synthon assembled from d-glucose via a stereoselective Johnson orthoester rearrangement is described. The studies set the stage for the completion of the total synthesis of the biologically important novel ansamycins, divergolides C and D, and their structural congeners