Aqueous Potassium Cyanide Research Articles

Metal effects on the asymmetric syntheses of chiral P−N bidentate ligands

The organoplatinum complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene as the chiral auxiliary has been used to promote the asymmetric cycloaddition reactions between 3,4-dimethyl-1-phenyl phosphole and (E)-1-phenyl-3-pyridin-2-yl-2-propenone or (E)-1-methyl-3-pyridin-2- yl-2-propenoate in high selectivity under mild condition. However, the corresponding palladium complex didn't show similar reactivity. This Diels−Alder reaction generated five new stereogenic centers in a single step. The naphthylamine auxiliary could be removed chemoselectively from the template products by treatment with concentrated hydrochloric acid to form the corresponding dichloro platinum complexes [(P−N)PtCl2]. The molecular structure and absolute configuration of the major dichloro platinum complex have been resolved by single-crystal X-ray diffraction. Finally, the enantiomerically pure P−N ligands can be readily liberated from the corresponding dichloro platinum complexes as air-sensitive solids by treatment with aqueous potassium cyanide in quantitative yield.

Palladacyclo-promoted asymmetric hydrophosphination reaction between diphenylphosphine and 2-ethynylpyridine

The organopalladium complex containing ortho-metalated (R)-[1-(dimethylamino) ethyl]naphthalene as the chiral auxiliary has been used as the chiral template to promote the asymmetric hydrophosphination reaction between diphenylphosphine and 2-ethynylpyridine in high selectivity under mild conditions. The double hydrophosphination reaction produces four stereoisomeric products in the ratio of 1:19.4:2.4:1.3. The naphthylamine auxiliary could be removed chemoselectively from the template products by treatment with concentrated hydrochloric acid to form the corresponding chiral dichloro complexes [(P–P)PdCl2]. The molecular structure and absolute configuration of the dichloro complex have been resolved by single-crystal X-ray crystallography. It confirms that the asymmetric diphosphines as P–P bidentate chelate on the chiral naphthylamine palladium templates. Finally, the enantiomerically pure diphosphine ligand with chirality on the carbon backbone can be readily liberated from the dichloro palladium complex as an air-sensitive solid by treatment of the complex with aqueous potassium cyanide in high yield.

Metal Effects on the Asymmetric Cycloaddition Reaction between 3,4-Dimethyl-1-phenylphosphole and Sulfoxide

The orthometalated [1-(dimethylamino)ethyl]naphthalene platinum(II) complex has been used successfully to promote the asymmetric cycloaddition reaction between 3,4-dimethyl-1-phenylphosphole and sulfoxide in high selectivity. The exo-cycloadduct coordinated to the platinum template as bidentate chelates via their phosphorus and sulfur atoms. The dichloro platinum complexes could be crystallized and were stable in the solid state as well as in solution. Optically pure P–S bidentate ligands could be liberated from these dichloro complexes by treatment with aqueous potassium cyanide. The study also highlights the difference in reactivity and mode of substrate activation between an earlier study involving a Pd analogue of the template and the current results.

Multiparameter Behavioral Analyses Provide Insights to Mechanisms of Cyanide Resistance in Caenorhabditis elegans

Environmental toxicants influence development, behavior, and ultimately survival. The nematode Caenorhabditis elegans has proven to be an exceptionally powerful model for toxicological studies. Here, we develop novel technologies to describe the effects of cyanide toxicity with high spatiotemporal resolution. Importantly, we use these methods to examine the genetic underpinnings of cyanide resistance. Caenorhabditis elegans that lack the EGL-9 oxygen sensing enzyme have been shown to be resistant to hydrogen cyanide (HCN) gas produced by the pathogen Pseudomonas aeruginosa PAO1. We demonstrate that the cyanide resistance exhibited by egl-9 mutants is completely dependent on the HIF-1 hypoxia-inducible factor and is mediated by the cysl-2 cysteine synthase, which likely functions in metabolic pathways that inactivate cyanide. Further, the expression of cysl-2 correlates with the degree of cyanide resistance exhibited in each genetic background. We find that each mutant exhibits similar relative resistance to HCN gas on plates or to aqueous potassium cyanide in microfluidic chambers. The design of the microfluidic devices, in combination with real-time imaging, addresses a series of challenges presented by mutant phenotypes and by the chemical nature of the toxicant. The microfluidic assay produces a set of behavioral parameters with increased resolution that describe cyanide toxicity and resistance in C. elegans, and this is particularly useful in analyzing subtle phenotypes. These multiparameter analyses of C. elegans behavior hold great potential as a means to monitor the effects of toxicants or chemical interventions in real time and to study the biological networks that underpin toxicant resistance.

Palladacycle mediated synthesis of cyano-functionalized chiral 1,2-diphosphine and subsequent functional group transformations

Cyano-functionalized allylic phosphine substrates containing the ortho-metalated ( R)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary were synthesized from bromoacetaldehyde dimethylacetal via a one-pot process. The diastereoselective hydrophosphination reactions of the cis- and trans-allylic phosphine substrates gave the cyano-functionalized chiral 1,2-bis(diphenylphosphino)ethane products with high yield and stereoselectivity. The subsequent organic transformation reactions of the cyano-substituted products chemoselectively afforded the formyl- and hydroxyl-functionalized chiral 1,2-diphosphine complexes with retention of stereochemistry. The coordination properties and absolute configurations of the novel 1,2-diphosphine complexes were established by single crystal X-ray crystallography. The optically pure 1,2-bis(diphenylphosphino)ethane ligands with cyano-, formyl- and hydroxyl-functionalities could be liberated in high yields from the corresponding dihalo palladium complexes by treatment with aqueous potassium cyanide.

Asymmetric Synthesis of Functionalized 1,3-Diphosphines via Chiral Palladium Complex Promoted Hydrophosphination of Activated Olefins

Aldehyde, ester- and keto-functionalized monophosphine palladium complexes containing the ortho-metalated (R)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary and reaction promoter were synthesized via hydrophosphination of acrolein and the subsequent Wittig reactions in a one-pot process. Under very mild conditions, the second-stage hydrophosphination of the monophosphine substrates gave the corresponding ester-, keto-, and hydroxyl-functionalized chiral 1,3-bis(diphenylphosphino)propane palladium complexes with good yields and stereoselectivities. The coordination properties and absolute configurations of the novel 1,3-diphosphine complexes were established by single crystal X-ray crystallography. The enantiomerically pure functionalized diphosphine ligands with ester and keto functionalities could be subsequently liberated stereospecifically by treatment of the corresponding dichloro palladium complexes with aqueous potassium cyanide in high yields.

Novel Enantioselective Synthesis of Functionalized Pyridylarsanes by a Chiral Palladium Template Promoted Asymmetric Hydroarsanation Reaction

AbstractThe asymmetric hydroarsanation reactions between diphenylarsane and (E)‐1‐phenyl‐3‐(pyridin‐2‐yl)‐2‐propenone and (E)‐1‐methyl‐3‐(pyridin‐2‐yl)‐2‐propenoate have been achieved by use of the organopalladium complex containing ortho‐metalated (R)‐[1‐(dimethylamino)ethyl]naphthalene as the chiral reaction template in high regio‐ and stereoselectivities under mild conditions. Hydroarsanation of (E)‐1‐phenyl‐3‐(pyridin‐2‐yl)‐2‐propenone with diphenylarsane generated two stereoisomeric products in the ratio of 3:1 as five‐membered As–N bidentate chelates on the chiral naphthylamine palladium template. Using the same chiral metal template, the corresponding hydroarsanation reaction with (E)‐1‐methyl‐3‐(pyridin‐2‐yl)‐2‐propenoate gave only one product as a six‐membered As–N bidentate chelate. The naphthylamine auxiliary could be removed chemoselectively by treatment with concentrated hydrochloric acid to form the corresponding optically pure neutral complexes. Subsequent ligands displacement from the palladium using aqueous potassium cyanide generated the optically pure keto‐ and ester‐functionalized chiral pyridylarsane ligands. The absolute configuration and the coordination properties of the pyridylarsanes have been established by single‐crystal X‐ray analysis.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Solubility of cyclooctasulfur in pure water and sea water at different temperatures

The solubility of cyclooctasulfur in water and sea water at various temperatures in the range between 4 and 80 °C was determined. Cyclooctasulfur in equilibrium with rhombic sulfur reacted with hot acidic aqueous potassium cyanide to form thiocyanate anion which was measured by anion chromatography. Sulfur solubility in pure water was found to increase with temperature by more than 78 times: from 6.1 nM S 8 at 4 °C to 478 nM S 8 at 80 °C. The following thermodynamic values for solubilisation of S 8 in water were calculated from the experimental data: K° = 3.01 ± 1.04 × 10 −8, Δ G r° = 42.93 ± 0.73 kJ mol −1, Δ H r° = 47.4 ± 3.6 kJmol −1, Δ S r° = 15.0 ± 11.7 J mol −1 K −1). Solubility of cyclooctasulfur in sea water was found to be 61 ± 13% of the solubility in pure water regardless of the temperature.

Advantage of in situ generation of N-arylsulfonyl imines from α-amide sulfones in the phase-transfer-catalyzed asymmetric Strecker reaction

Highly efficient, catalytic enantioselective synthesis of N-arylsulfonyl α-amino nitriles from the corresponding α-amido sulfones has been achieved under toluene–aqueous potassium cyanide biphasic conditions using chiral quaternary ammonium iodide ( R, R, R)- 1 as an effective phase-transfer catalyst. This Strecker synthesis involving the in situ generation of the reactive N-sulfonyl imines is advantageous for the cyanation of the substrates having primary and secondary alkyl substituents.

A Novel Approach toward Asymmetric Synthesis of Alcohol Functionalized C-Chiral Diphosphines via Two-Stage Hydrophosphination of Terminal Alkynols

Alcohol functionalized diphosphine ligands with chirality residing on the carbon backbone were prepared using a novel two-stage asymmetric synthetic methodology from the corresponding terminal alkynols. Under mild conditions, the alkynols, 3-butyn-1-ol and 2-propyn-1-ol, were subjected to direct hydrophosphination to give the corresponding Markovnikov addition products. The phosphine functionalized alkenols thus obtained were subsequently subjected to a second-stage asymmetric hydrophosphination employing an organopalladium complex containing the ortho-metalated (R)-(1-(dimethylamino)ethyl)naphthalene as a chiral auxiliary and reaction promoter. In the reaction that involved 3-diphenylphosphanyl-but-3-en-1-ol, all four possible stereoisomeric products were generated stereoselectively in the ratio of 1:2:4:18. The major isomer was subsequently isolated in appreciable yield in its configurationally pure form and characterized by means of single-crystal X-ray crystallography. The naphthylamine auxiliary could be removed chemoselectively from the template product by treatment with concentrated hydrochloric acid to form the corresponding optically pure neutral complex. Subsequent ligand displacement from the palladium achieved using aqueous potassium cyanide generated the optically pure diphosphine ligand with chirality residing on the carbon backbone in appreciable yield. However, the similar asymmetric hydrophosphination reaction involving 2-diphenylphosphanyl-prop-2-en-1-ol did not exhibit appreciable selectivity.

Asymmetric synthesis of a chiral arsinophosphine via a metal template promoted asymmetric Diels–Alder reaction between diphenylvinylphosphine and 2-furyldiphenylarsine

The asymmetric Diels–Alder reaction between 2-furyldiphenylarsine and diphenylvinylphosphine was achieved stereospecifically by utilizing an organoplatinum reaction promoter containing the ortho-metalated ( R)-(1-(dimethylamino) ethyl)-naphthalene as the chiral auxiliary. The optically pure (+)-As–P heterobidentate cycloadduct could be liberated from the template product by successive treatment with concentrated hydrochloric acid and aqueous potassium cyanide.

Asymmetric Strecker Reaction of Aldimines Using Aqueous Potassium Cyanide by Phase‐Transfer Catalysis of Chiral Quaternary Ammonium Salts with a Tetranaphthyl Backbone.

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Asymmetric Strecker Reaction of Aldimines Using Aqueous Potassium Cyanide by Phase-Transfer Catalysis of Chiral Quaternary Ammonium Salts with a Tetranaphthyl Backbone

The phase-transfer-catalyzed, highly enantioselective cyanation of aldimines using aqueous KCN has been realized based on the molecular design of chiral quaternary ammonium iodide 2c bearing a stereochemically defined tetranaphthyl backbone. For example, vigorous stirring of a mixture of cyclohexanecarboxaldimine (R = c-Hex) and (R,R,R)-2c (1 mol %) in toluene-KCN aqueous solution (1.5 equiv) at 0 degrees C for 2 h gave rise to the corresponding protected amino nitrile (R = c-Hex) in 89% yield with 95% ee. A wide range of aliphatic aldimines, including those having alpha-tert-alkyl substituents, is tolerated by the present system. This study represents a novel approach for the asymmetric Strecker-type reactions, which utilizes chiral phase-transfer catalysts for practical access to various unusual, optically pure alpha-amino acids.

Preparation of Cyanopyridines by Direct Cyanation.

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Preparation of Cyanopyridines by Direct Cyanation

After pretreatment with nitric acid and trifluoroacetic anhydride, aqueous potassium cyanide converted pyridines 1a-l into their corresponding 2-cyano derivatives 4a-l in an average yield of 52%.

Asymmetric synthesis and the coordination chemistry of a P-chiral diphosphine monoxide

The organopalladium complex containing ortho-metalated ( R)-(1-(dimethylamino)ethyl)-naphthalene as the chiral auxiliary has been used successfully to promote the asymmetric [4+2] exo-cycloaddition reaction between 1-phenyl-3,4-dimethylphosphole and vinyldiphenylphosphine oxide. The resulting P-chiral phosphanorbornene was obtained as a P–O bidenate chelate on the palladium template. The phosphanorbornene (−)-(L) could be liberated from the palladium template as a highly air-sensitive oil by the treatment of the template complex with aqueous potassium cyanide. Upon recoordination to the Au(I) ion, the diphosphine monoxide coordinated to Au(I) as a monodentate ligand via its tertiary phosphorus donor atom to form the linear complex (+)-[(L– P)AuCl]. The chloro ligand and the pendant PO group in the gold complex showed significant hydrophilicity as they both formed hydrogen bondings to a water molecule. However, the neutral gold complex is not soluble in water.

Organopalladium Complex Promoted Asymmetric Cycloaddition Reactions Involving 3,4-Dimethyl-1-phenylphosphole 1-Sulfide as the Heterocyclic Diene

3,4-Dimethyl-1-phenylphosphole 1-sulfide (DMPPS) reacted as a heterocyclic diene in the asymmetric Diels−Alder reaction with diphenylvinylphosphine in the presence of an organopalladium(II) complex derived from the enantiomerically pure ortho-metalated (R)-(1-(dimethylamino)ethyl)naphthalene. The cycloaddition reaction proceeded at room temperature via an intramolecular mechanism in which the cyclic diene and the dienophile were coordinated simultaneously on the chiral palladium template. The (RP)-exo cycloadduct was obtained with high stereoselectivity as a P−S bidentate chelate on the palladium template. When DMPPS was treated with the heterodienophile thiobenzophenone at 50 °C in the presence of the organopalladium(II) complex, the corresponding heterocycloaddition reaction proceeded to generate the expected cycloadduct as a rigid S−S bidentate chelate on the palladium template. However, the cyclic adduct was obtained as a racemic mixture. The low stereoselectivity in the heterocycloaddition reaction is attributed to the kinetic instability of S→Pd coordination bonds in the intermediate template complex. Both the P−S and S−S cycloadducts could be liberated from the corresponding template complexes by treatment of the template complexes with aqueous potassium cyanide.

Optical Resolution, Configurational Stability, and Coordination Chemistry of the P-Chiral Heterocyclic Diphosphine 1,1‘-Diphenyl-3,3‘,4,4‘-tetramethyl- 2,2‘-diphosphole-3,3‘-diene

The optical resolution of the C2-symmetrical racemic ligand (RP*SC*)-1,1‘-diphenyl-3,3‘,4,4‘-tetramethyl-2,2‘-diphosphole-3,3‘-diene (±)-(1) has been achieved efficiently via fractional crystallization of a pair of diastereomeric palladium(II) complex cations containing the appropriate form of the chelating diphosphine ligand and orthometalated (S)-(1-(dimethylamino)ethyl)naphthalene. The absolute stereochemistries of both diastereomeric complexes have been confirmed by single-crystal X-ray crystallography. The liberation of the optically active diphosphine ligand from the corresponding resolved complexes involved two steps: the removal of the naphthylamine ligand with concentrated hydrochloric acid followed by the decomposition of the intermediate [Pd(1)Cl2] species with aqueous potassium cyanide. Thus, (RPSC)-(−)-(1) and (SPRC)-(+)-(1) were obtained in high yields with [α]D = ±124.3° (C6H6). These resolved ligands are configurationally stable, as their optical purities remained unchanged upon heating at 140 °C for 48 h in benzene and in propanol. They are able to form the optically active digold complexes [Au2(μ-1)Cl2], despite the fact that the two rigid heterocyclic rings are linked with a carbon−carbon bond of restricted rotation.

Reactions with 2(1H)-Quinolinone and Coumarine Derivatives: New Routes to Polysubstituted 2(1H)-Quinolinone and Coumarine Derivatives

Abstract Whereas 2H-pyrano[3,2-c]quinoline-2,5(6H)-dione (2a) or 3-acetyl-1-methyl-2(1H)-quinolinone (3a) reacted with the benzylidenenitriles 1a—f or a mixture of either malononitrile or ethyl cyanoacetate and aromatic aldehydes in ethanol/piperidine to give 4H-pyran derivatives 8, the reaction of 2b,c or 3b,c with the same reagents afforded 4,6-dihydro-5H-pyrano[3,2-c]quinolin-5-ones 11. Compounds 11 were also prepared from 1a—f and 3d,e,f. Reaction of pyrano[3,2-c]coumarin 2d with 1a yielded 6H,11H-[2]benzopyrano[4,3-c][1]benzopyran-6,11-dione (15). Treatment of 17 with aqueous potassium cyanide or hydroxylamine afforded the 2(1H)-quinolinone derivatives 19 and 20 respectively.

Scanning electrochemical microscopy. 19. Ion-selective potentiometric microscopy

Potentiometric pH selective tips for scanning electrochemical microscopy (SECM) have been developed and used to image local pH changes in a variety of model chemical systems. Images of pH profiles around a platinum microelectrode during water reduction, a corroding disk of silver iodide in aqueous potassium cyanide, a disk of immobilized urease hydrolyzing urea, and a disk of immobilized yeast cells in glucose solution were obtained. A simple method for fabricating antimony microdisk electrodes suitable for use in SECM is described. The general theory for SECM with potentiometric ion selective tips is also present, assuming that the tip is a purely passive sensor