Alternate method of source preparation for alpha spectrometry: no electrodeposition,no hydrofluoric acid

Journal of Radioanalytical and Nuclear Chemistry - An alternate method of preparing actinide alpha counting sources was developed in place of electrodeposition or lanthanide fluoride...     

CO(2) capture by a task-specific ionic liquid

Reaction of 1-butyl imidazole with 3-bromopropylamine hydrobromide, followed by workup and anion exchange, yields a new room temperature ionic liquid incorporating a cation with an appended amine group. The new ionic liquid reacts reversibly with CO2, reversibly sequestering the gas as a carbamate salt. The new ionic liquid, which can be repeatedly recycled in this role, is comparable in efficiency for CO2 capture to commercial amine sequestering reagents, and yet is nonvolatile and does not require water to function.     

Synthese von terpenartigen bicyclischen Systemen über die Cycloaddition von Dimethylketen an Methylcyclopentadien

The structure of the cyclo-addition products of ketenes ( 2 ) and methylcyclopentadiene could not be predicted, since this ketenophile exists as a rapidly equilibrating 45:54:1 mixture of the 1- ( 4 ), 2- ( 5 ) and 5-methyl ( 6 ) isomers. We studied this reaction using dimethylketene ( 2a ) with a view to monoterpenoid synthesis. Only two ( A and B ) of the many possible cyclo-adducts were formed in good yield. Using three methods to generate dimethylketene, the ratios of A:B were 90:6, 77:16 and 55:31 respectively. The structures of A and B were proved without making use of the known ketene cyclo-addition rules: Of the many possibilities, all but 7, 8, 9 and 10 were excluded by the C?O and C?C? CH₃ IR.-bands and NMR. signals. Structure 7 (filifolone) was rejected by the difference of its NMR. spectrum from those of both A and B , leaving only 8 , 9 and 10 . For A , structures 9 and 10 were eliminated by two chemical approaches: (1) Peracetic acid oxidation of a mixture rich in A resulted in a combination of Baeyer-Villiger reaction, epoxidation, and epoxide-ketone rearrangement affording a C₁₀-keto-lactone 14 , which was cleaved by alkali to acetone and a C₇-keto-acid 18 . (2) Another peracetic acid treatment produced a keto-epoxide 11, which was converted to a diol 22 and then to a diketo-aldehyde 23 with an NMR. doublet for the aldehyde proton. Of the two structures ( 9 and 10 ) left for B , the latter was excluded by the NMR. spectrum of keto-epoxide 15 isolated from the peracid treatment of a mixture rich in B : A decoupling experiment with 15 showed that the -CH₂- was placed next to the α-carbon of the carbonyl function. Thus the major cyclo-adduct of dimethylketene and methylcyclopentadiene is 8 , and the minor product is 9 . This result demonstrates further ketene cyclo-addition specificities on top of the ones expressed by the three known rules. The different ratios of 8 : 9 are considered to be due to varyingly effective competition between the preliminary interconversion of the methylcyclopentadienes and their cyclo-addition of dimethylkctene. A number of other oxidation and reduction products of 8 are described. One of them proved that C7 had migrated in the Baeyer-Villiger reaction. A partial separation of the enantiomers of the major cycloadduct 8 was achieved. By the use of 0.5 equivalent of three chiral primary amines (31, 32, and 33) to form a Schiff base, the excess ketone 8 was in each case distilled off in a chirally enriched form with positive optical rotation. The derived 2.3-dihydroketone 36 was shown to have a positive Cotton effect and, by an application of the octant rule, to have the (1R,5S) chirality orientation.     

Zur Reaktionsweise von Diphenylcyclopropenon mit β-Carbonyl-enolaten. I. Einsatz von Acetylaceton,Acetessigsäure-methylester, 2-Äthoxycarbonyl-cyclododecanon und Malonsäure-dimethylester

Reaction of Diphenylcyclopropenone with β-Carbonyl-enolates. I. Use of Acetylacetone, Methyl Acetoacetate, 2-Ethoxycarbonyl-cyclododecanone and Dimethyl Malonate The reaction of the sodium salts of acetylacetone ( 6 ), methyl acetoacetate (7) , 2-ethoxycarbonyl-cyclododecanone (8) , dimethyl malonate (19) and its methyl derivative 20 with diphenylcyclopropenone ( 5 ) in dimethylformamide at room temperature led to the unsaturated γ-lactones 14, 15, 17, 22 and 36 . In the case of dimethyl malonate ( 19 ), the halfester 21 , the acyl-malonic ester 24 and the indenone-malonic ester 23 were also isolated. Several intermediates and the final products were characterised by reactions and spectroscopically. A general mechanism is discussed for the addition of cyclo-propenones ( 1 ) to the enolate salts of β-dicarbonyl compounds 4 involving the bicyclic lactone-enolates 18 and 32 as intermediates. The products formed via 18 and 32 are considered to be the result of an attack of one of the oxygen atoms of the β-carbonyl-enolate anion ( 4 ), the product 24 , on the other hand, of the attack of the α-carbon atom of 4 ; in both cases the attack is on the carbonyl C-atom of 5 .     

A simple approach to sensor discovery and fabrication on self-assembled monolayers on glass

Self-assembled monolayers (SAMs) on glass were used as a platform to sequentially deposit fluorophores and small molecules for ion sensing. The preorganization provided by the surface avoids the need for complex receptor design, allowing for a combinatorial approach to sensing systems based on small molecules. The resulting libraries are easily measured and show varied responses to a series of both cations and anions. This technology is transferable from the macro- to the microscale both via microcontact printing (microCP), where the fluorophore is printed onto a glass surface, and via direct attachment of the fluorophore to microchannel walls. The ease of miniaturization of this technology may make the generation of a wide variety of simple yet efficient microarrays possible.     

Rhodium catalysed tandem conjugate addition-protonation: an enantioselective synthesis of 2-substituted succinic esters

The rhodium catalysed addition of potassium trifluoro(organo)borates to dimethyl itaconate generates an intermediate complex which on protonation provides enantioenriched succinic esters.     

A tandem metal carbene cyclization-cycloaddition approach to the pseudolaric acids

An approach toward the synthesis of the antifungal and cytotoxic pseudolaric acids based on the tandem metal carbene cyclization-cycloaddition reaction is described. Using this strategy, the advanced intermediate 3a bearing three of the four stereocenters of the target molecules has been synthesized. The substrate-controlled diastereoselectivity of the tandem carbene cyclization-cycloaddition was preferential for the undesired diastereomer, but reagent control through the use of Hashimoto's chiral rhodium catalyst Rh(2)(S-BPTV)(4) reversed the selectivity in favor of 3a. Ring opening of the oxabicyclic nucleus to give a hydroxycycloheptene has been demonstrated in a model study.     

Catalytic enantioselective [3 + 2]-cycloadditions of diazoketone-derived aryl-substituted carbonyl ylides

An evaluation of alpha-aryl-alpha-diazodiones in tandem carbonyl ylide formation-enantioselective [3 + 2]-cycloaddition reactions is described. Such substrates were designed to allow investigation of the electronic characteristics of the dipole upon asymmetric induction. Intramolecular cycloadditions (with a tethered alkene dipolarophile) were found to occur in good to quantitative yields, with a difference in ee exhibited by the two electronically different diazodiones 8 and 9. Intermolecular cycloadditions using diazodiones 12 and 13 with DMAD and arylacetylenes 16-18 again demonstrated that electronics play a key role in determining the outcome of the cycloaddition reactions. Enantioselectivities of up to 76% were observed.