Syntheses, spectroscopic characterization and metal ion binding properties of benzo-15-crown-5 derivatives and their sodium and nickel(II) complexes

New benzo-15-crown-5 derivatives containing nitro, amine and imine groups were prepared. Nitro compound (1) was prepared after the reaction?4′,5′-bis(bromethyl)benzo-15-crown-5 and o-nitrophenol in the presence of NaOH. After reduction process by using hydrazine hydrate and Pd/C amine compound (2) was formed. New crown ether imine compounds (3–5) were synthesized by the condensation of corresponding crown ether diamine (2) with salicylaldehyde derivatives. Sodium complexes of the crown compounds (1a–5a) form crystalline 1:1 (Na⁺: ligand) complexes with sodium perchlorate. Nickel(II) complexes (3b–5b) with 1:1 (Ni²⁺:ligand) stoichiometries were also been synthesized from the Schiff bases (3–5). The results indicated that the Schiff base ligands coordinated through the azomethine nitrogen and phenolic oxygen. The extraction ability of compounds (1, 3, 4 and 5) were also evaluated in chloroform by using several alkali and transition metal picrates such as Li⁺, Na⁺, K⁺, Cr³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pb²⁺.     

Syntheses and spectroscopic characterization of double-armed benzo-15-crown-5 derivatives and their sodium and potassium complexes

A series of new benzo-15-crown-5 derivatives (1–6) containing formyl and imine groups were prepared. New formyl crown ethers (1 and 2) were prepared by reaction of 4′,5′-bis(bromomethyl)benzo-15-crown-5 with 2-hydroxy-3-methoxybenzaldehyde (o-vanillin) and 2-hydroxy-5-methoxybenzaldehyde in the presence of NaOH. New Schiff bases (3–6) were synthesized by the condensation of corresponding aldehydes with 1,3-diaminopropane and 1,4-diaminobutane. Sodium and potassium complexes (1a–6a and 1b–6b) of the crown compounds forming crystalline complexes of 1:1 (Na⁺:ligand) and 1:2 (K⁺:ligand) stoichiometries were also synthesized. The structures of the aldehydes 1 and 2, imines 3–6 and complexes (1a–3a and 1b–3b) were confirmed on the basis of elemental analyses, IR, ¹H- and ¹³C-NMR, and mass spectroscopy.     

Alkali metal complexation properties of resorcinarene bis-crown ethers: effect of the crown ether functionality and preorganization on complexation

The synthesis and characterization of tetramethoxy resorcinarene tribenzo-bis-crown ethers, m- and p-TBBC6, are described. The effect of the added aromatic functionality in the crown ether bridge on the alkali metal complexation properties was investigated and compared to the properties of tetramethoxy resorcinarene bis-crown-5 (BC5) by means of ¹H NMR spectroscopy and X-ray crystallography. It was found that BC5 and m-TBBC6 were capable of binding alkali metal cations (K⁺, Rb⁺, and Cs⁺), with the highest affinity toward Cs⁺ cation, while no binding was observed in the case of p-TBBC6, which confirms the significance of the complementarity and preorganization for complexation affinity.     

The electronic structure of 5-methylhexa-1,2,4-triene-1,3-diyl, the first representative of highly delocalized triplet ethynylvinylcarbenes, from ESR spectroscopy data and quantum chemical calculations

The ESR spectrum of the first representative of highly conjugated triplet ethynylvinylcarbenes, 5-methylhexa-1,2,4-triene-1,3-diyl (1), was recorded in solid argon matrix. The zero-field splitting (ZFS) parameters of carbene 1 (D = 0.5054±0.0006 cm^?1 and E = 0.0045±0.0002 cm^?1) determined from the experimental ESR spectrum are in between the corresponding parameters of ethynylcarbene C3H2 (2) and vinylcarbene C₃H₄ (3): D(3) < D(1) < D(2) and E(2) < E(1) < E(3). Quantum chemical calculations of the ZFS parameters of 1, 2, and 3 have been carried out for the first time using two DFT-based approaches, RODFT and UDFT. An analysis of the experimental and theoretical ZFS parameters shows that carbene 1 is characterized by a greater extent of delocalization of the spin density of unpaired electrons than carbenes 2 and 3. The characteristic structural fragments of carbene 1 possess the principal features of the electronic structure of both ethynylcarbene (2) and vinylcarbene (3), respectively. Magnetic spin-spin interactions are identical in carbenes 1 and 2. The dominant contribution to D in 1 and 2 results from the one-center spin-spin interactions on carbon atoms in the propynylidene group, which are subjected to strong spin polarization.     

Synthese von 1-substituierten 4-Amino-2(1H)-pyridinthionen durchDimroth-Umlagerung aus 2,4-Diaminothiopyranyliumhalogeniden

4-Amino-2-alkylimino-2H-thiopyranes (5) and 4-amino-2-alkylaminothiopyranylium halogenides (4) resp. on heating in refluxingDMFA are rearranged in the presence of Na-ethylate to 1-alkyl-4-aminodihydro-2(1H)-pyridinethiones (2). Also 2-methylthiothiopyranylidenammonium iodides (6) and 2-methylthio-4H-thiopyrane-4-one (7) can be transformed into 1-substituted 2(1 H)-pyridinethiones (2) by heating in prim. amines. On treatment with alkali. 4-dimethylaminothiopyranylium iodide (4 a) is transformed into its base5 a and hydrolyzed to8. 5a and8 are rearranged to the pyridinethiones2 a and the tautomers9 A,B. The structure of the rearranged pyridinethiones2 was proved by the1-phenylderivate2 a. Thus 4-methyl-3-penten-2-on reacts with phenylthiourea via the phenylimino-1,3-thiazine (14) to give 3-phenyl-2(1H)pyridinethione (15).15 is transformed by themethylpyrimidine-pyridine-rearrangement to the 1-phenylpyridinethione2 a. The mechanism of theDimroth-reaction of 2-alkylimino-2H-thiopyranes (5) and the stereochemistry of the1-benzyl-6-phenyl-2(1H)-pyridinethiones2 are discussed.     

Lariat ethers in the chiral recognition of amino acid esters:electrospray ionization mass spectrometry investigation

The ability of the crown ethers (1–4), containing the ortho- or para- methoxyphenoxy-methyl substituents in their structure, to chiral recognition in reference to amino acid esters has been investigated by electrospray ionization mass spectrometry (ESI-MS). The method allows registering the diastereomeric complexes between the studied crowns as hosts and the protonated alanine, phenylglycine and phenylalanine methyl esters as guests in the gas phase. ESI-MS experiments using isotopically labeled guests provide robust and reproducible results, indicating a moderate degree of chiral discrimination in the series of the studied crown ethers. ESI-MS experiments using achiral amine as a reference yielded the results comparable with the previous method. It has been found that (S)-enantiomers of the crowns bind predominately (S)-enantiomers of the amino acid esters, and vice-versa. It has been shown that the chiral ortho-substituted crown (S)-1 demonstrates the more pronounced values for chiral discrimination as compared with the para-substituted crown (S)-2. This fact indicates the interrelationship between the chiral recognition and the lariat nature of crown 1. Increasing the size of the cavity and the presence of a flat aromatic moiety in crowns 3 and 4 strengthens their complexing ability, simultaneously weakening the enantioselectivity of the complexation.     

Zur Chemie der 5-Alkylamino-4H-thiopyrano[2,3-b]pyridin-4-one

4-Alkylaminopyridinethiones · HCl (1 · HCl) react with bis-trichlorethylmalonate (3) predominantly to 5-alkylamino-4H-thiopyrano [2,3-b]pyridine-4-ones (6). With alcohols in the presence of acids at 25°C6 undergoes an alcoholysis to the corresponding alkyl-3-(2-thioxo-3-pyridyl)propionates (9). On heating in dilute alkali6 is hydrolysed via 4-alkylamino-2-thioxopyridyl-propylketones (11) to the tautomers, 4-hydroxy-2-thioxopyridylpropylketone (12 A) and 2-thioxo-3-(1-hydroxybutenyl)-4-piperidon (12 B), resp. On refluxing with alkali the ethyl-pyridylpropionate9 a is cyclisized to the 1-alkyl-1,6-naphthyridine-2(1H)-one (4 a), but boiling in ethanolic acid hydrolyses9 a via the pyridylpropionic acid10 to 4-alkyl-aminopyridylpropylketone (11 a). The latter can be transformed via the tautomers12 A,B and 2-methylthio-3-pyridylpropylketone (13) to the 4-hydroxy-3-butyrylpyridone (14 A) and its tautomer, 3-(1-hydroxy-butenyl)-piperidine-2,4-diones (14 B) resp. The structure of14 A,B is established by reaction of 4-isopropylamino-2(1H)-pyridone (2) with butanoylchloride to the 4-isopropylamino-3-butyrypyridone (15) and hydrolysis of15 to the tautomers14 A,B.     

A convergent paired electrochemical synthesis of new heterocyclic compounds. Reaction of benzoquinones with 3-Amino-4-hydroxycoumarin

Electrochemical oxidation of catechols (1) has been studied in the presence of cathodically generated 3-amino-4-hydroxycoumarin (3a) as a nucleophile in aqueous solutions, using cyclic voltammetry and controlled-potential coulometry. The results indicate that the o-benzoquinones derived from catechols (1) participate in Michael addition reaction with 3-amino-4-hydroxycoumarin (3a) to form the corresponding new heterocyclic compounds (7) (oxidized form of coumestan derivatives). The electrochemical process consists of a multi-step including (a) cathodic reduction of 4-hydroxy-3-nitrocoumarin (3) to 3-amino-4-hydroxycoumarin (3a), (b) anodic oxidation of catechols (1) to related o-benzoquinone (2), (c) the Michael addition reaction of 3-amino-4-hydroxycoumarin (3a) to o-benzoquinone (2), and (d) anodic oxidation of formed adduct. The paired electrochemical synthesis of compounds 7a and 7b has been successfully performed in a one-pot process at carbon rods as working and counter electrodes in an undivided cell.     

Synthese von (5,10)-(7,8)-Bisepoxiden aus α- und β-4-Phenyl-1,2,4-triazolin-3,5-dion-Addukten von Vitamin D3 und Röntgenstrukturanalyse eines der Benzoylderivate

Oxidation of the α- and β-4-phenyl-1,2,4-triazolin-3,5-dione adducts of vitamin D₃ (2 and1) withMCPBA yields two diastereomeric mixtures of the (5,10)-(7,8)-dioxiranes3 a,3 b,3 c and4 a,4 b respectively. The corresponding benzoates5 a,5 b,6 a and6 b were prepared and the X-ray crystal structure of5 b was determined. This analysis proved5 b to be the (5R, 1 OS)-(7R, 8R)-dioxirane of the β-resp. (6S)-4-phenyl-1,2,4-triazolin-3,5-dione adduct1 of vitamin D₃.     

Preparation and reactions of optically active cyanohydrins using the (R)-hydroxynitrile lyase from Prunus amygdalus

Cyanuration of 2-naphthaldehyde (1) and 5-methyl-2-furaldehyde (2) yielded the racemic 2-hydroxy-2-(β-naphthyl)ethanenitrile (R,S)-3 and 2-hydroxy-2-(5-methyl-2-furyl)ethanenitrile (R,S)-5, respectively. The same reaction can be completed by using acetone cyanohydrin (4) as a transcyanating agent. The optically active (R)-3 and (S)-5 could be respectively obtained by hydrocyanation of 1 and 2 using (R)-hydroxynitrile lyase (R)-PaHNL [EC 4.1.2.10] from almonds (Prunus amygdalus) as a chiral catalyst. Cyanohydrins 3 and 5 in their racemic and optically active forms undergo a number of transformations which involve either the hydroxyl group or the cyanide function. Moreover, derivatization of 3 and 5 with (S)-Naproxen®chloride (S)-14 gave the respective diastereoisomers. The optical activity of (R)-3 and (S)-5 as well as their derivatives were recorded. The postulated structures for the new products were supported with compatible elementary and spectroscopic (IR, ¹H NMR, ¹³C NMR, MS, and single crystal X-Ray crystallography) analyses. The antimicrobial activity of some selected racemic new products and their respective optically active analogues were also undertaken.     

Syntheses, characterization and crystal structures of new mono- and bis-Schiff base compounds derived from 1,2,4-triazine and the silver(I) complexes containing mono-Schiff base ligands

Some new Schiff bases, (Z)-4-amino-3-((E)-(R-methoxybenzylidene)hydrazono)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L2), R?=?3 (L3) and R?=?4 (L4)), were synthesized by the condensation reactions of 4-amino-3-hydrazinyl-6-methyl-1,2,4-triazin-5(4H)-one (L1) and corresponding methoxybenzaldehyde in a molar ratio 1:1.5 in high yields. The reaction of L2 and L4 with an excess amount of the corresponding aldehydes gave the unsymmetrical bis-Schiff bases (E)-3-((E)-(R-methoxybenzylidene)hydrazono)-4-((E)-R-methoxybenzylideneamino)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L22) and R?=?4 (L44)), respectively. Furthermore, the reaction of L2?CL4 with silver(I) nitrate in a molar ratio 2:1 led to the silver(I)-complexes with the general formula [Ag(Lx)₂]NO₃ (Lx?=?L2 (2), L3 (3) and L4 (4)). All synthesized Schiff base compounds and complexes were characterized by a combination of IR-, ¹H-NMR spectroscopy, mass spectrometry and elemental analyses. In addition, the structures of L2, L4·CH₃CN, L22·CH₃OH and L44·CH₃OH and complexes 2 and 4 were determined by X-ray diffraction studies.     

Über cyclische Guanidin—Mesityloxid- und Guanidin—Phoron-Kondensate

The basic product synthesized byTraube andSchwarz from mesityl oxide and guanidine has not been 4.4.6-trimethyl-4.5-dihydro-2-pyrimidinamine (1), but a mixture containing the 4.4.6-trimethyl-3.4-dihydro-2(1H)-pyrimidinimine (resp. an isomeric pyrimidinamine)2 a (resp.2 b, 2 c) and the dimeric 4.4′-methylenedi[2(1H)-pyrimidinimine] (resp. an isomeric methylenedipyrimidinamine)3 a (resp.3 b, 2 c) and the dimerisation reaction were studied in a series of experiments. The product of the reaction of guanidine and phorone is not the guanidinopropylpyrimidine8 ⁴, but the 4.4′-spirobi[2(1H)-pyrimidinimine] (resp. a spirobipyrimidinamine)11 a (resp.11 b, 11 c). No determination was possible on the basis of NMR whether the condensation products of guanidine—in solutions ofDMSO-d₆—are pyrimidinimines (2 a, 3 a, 11 a) or pyrimidinamines (2 b resp.2 c, 3 b resp.3 c, 11 b resp.11 c) or mixtures of the isomeric compounds. The NMR-and mass spectra of2 a (resp.2 b, 2 c),3 a (resp.3 b, 3 c),11 a (resp.11 b, 11 c) and their derivates are discussed.     

Copper complexes of two isomeric NS2-macrocycles

Two isomeric NS₂-macrocycles incorporating a xylyl group at ortho (o -L) and meta (m -L) positions were employed and their copper complexes (1?C5) were prepared and structurally characterized. The copper(II) nitrate complexes [Cu(L)(NO₃)₂] (1: L = o -L, 2: L = m -L) for both ligands were isolated. In each case, the copper center is five-coordinated with a distorted square pyramidal geometry. Despite the overall geometrical similarity, 1 and 2 show the different ligand conformation due to the discriminated packing pattern. Reaction of o -L with copper(II) perchlorate afforded complex 3 containing two independent complex cations [Cu(o -L)(H₂O)(DMF)(ClO₄)]⁺ and [Cu(o -L)(H₂O)(DMF)]²⁺; the coordination geometry of the former is a distorted octahedron while the latter shows a distorted square pyramidal arrangement. In the reactions of copper(I) halides (I or Br), o -L gave a mononuclear complex [Cu(o-L)I] (4) with a distorted tetrahedral geometry, while m -L afforded a unique exodentate 2:1 (ligand-to-metal) complex [trans-Br₂Cu(m-L)₂] (5) adopting a trans-type square-planar arrangement.     

Chemie des 5,7-Dihydroxy-2H-thiopyrano[2,3-b]pyridin-4(3H)-ons

Hydrolysis of the 4-alkyliminothiopyrano[2,3-b]pyridinedioles (5) and 4-alkylaminothiopyrano[2,3-b]pyridones (6) resp. with 10% NaOH gives 5,7-dihydroxy-2H-thiopyrano[2,3-b]pyridine-4(3H)-one (7).7 can be obtained in better yield by reaction of 4-dimethylamino-2(1H)-pyridinethione (8) with bistrichlorphenylethylamlonate (2). Aminolysis of7 affords the two isomeric products5 and6. On treatment with hydrazines,7 reacts only to 4-hydrazonoderivatives5. By heating in bromobenzene5d is cyclisized to 1H-5,1,2,6-thiatriaza-acenaphthylen-7-ol (11). On methylation with methyljodide5,6 and7 furnish the 7-methoxyproducts13,14 and12. By heating in 20% NaOH7 is transformed into the 2-thioxo-3-pyridylmethylketone16 A and its tautomer, 2-mercapto-3-pyridylmethylketone16 B. The structures of5,6 and7 are discussed.     

Tribromogermyl monochelates — derivatives of N,N-disubstituted 2-hydroxycarboxylic amides

Reactions of GeBr₄ with N,N-dimethyl-2-trimethylsiloxypropionamide (2a), (S)-2-trime-thylsiloxypropionpyrrolidide ((S)-2b), and N,N-dimethyl-O-(trimethylsilyl)mandelamide (2c) afforded pentacoordinated neutral (O,O)-monochelates, viz., N,N-dimethyl-2-tribromoger-myloxypropionamide (3a), (S)-2-tribromogermyloxypropionpyrrolidide ((S)-3b), and N,N-dimethyl-O-(tribromogermyl)mandelamide (3c), respectively. X-ray diffraction study was performed for tribromides 3a, (S)-3b, and 3c, as well as for the N,N-dimethylmandelamide (1c) described earlier. According to the X-ray diffraction data, the Ge atom in tribromides 3a, (S)-3b, and 3c is pentacoordinated and has trigonal bipyramidal configuration with two halogen atoms and oxygen atom of the ether group in the equatorial positions and the halogen atom and the amide oxygen atom in the axial fragment, the bonds in which are somewhat longer as compared to the analogous bonds in tetracoordinated Ge compounds.     

Construction and characterization of novel molecular architectures through coordination-driven self-assembly: rhomboid and overlapped double rhomboid

The potentially tridentate ligands 4-(6-(pyridin-4-yl)pyridin-2-yl)pyridine (4) and 3-(6-(pyridin-3-yl)-pyridin-2-yl)pyridine (5) have been prepared and characterized. From the self-assembly of 4 or 5 and 2,9-bis[trans-Pt(PEt₃)₂(NO₃)]phenanthrene (6), two supramolecular platinum-based macrocycles with rhomboid (7) and overlapped double rhomboid (8) structures have been constructed. Compounds 7 and 8 are formed in different shapes due to the different nitrogen positions (meta and para) of the ligands 4 and 5, respectively. Both supramolecules are characterized by multinuclear NMR and electrospray ionization mass spectroscopies.     

Copper(II), iron(III) and cobalt(III) complexes of the pendent-arm cyclam derivative 6,6,13-trimethyl-13-amino-1,4,8,11-tetraazacyclotetradecane

The interaction of Cu(II), Fe(III) and Co(III) with 6,6,13-trimethyl-13-amino-1,4,8,11-tetraazacyclotetradecane (L ³ ) incorporating a pendent amine group has led to isolation of the new octahedral complexes [Cu(HL ³ )(ClO₄)₂]Cl·H₂O (1), [Fe(L ³ )Cl](S₂O₆)·H₂O (2), [Co(L ³ )Cl](ClO₄)_1.5Cl_0.5·0.25H₂O (3), [Co(HL ³ )Cl₂](ClO₄)₂·H₂O (4) and [Co(L ³ )Cl]₂(S₂O₄)(ClO₄)₂ (5). In (1) the copper ion occupies the macrocyclic cavity of protonated (–NH₃ ⁺) L ³ which is present in its trans-III configuration; weakly bound ClO₄ ^? ligands occupy the axial positions. The X-ray structure of (2) showed that Fe(III) occupies the N₄-macrocyclic cavity of L ³ in a trans-III configuration, with the pendent amine group binding in an axial position. The remaining axial position is occupied by a Cl^? ligand. Chromatography of the product obtained from the reaction of Na₃[Co(CO₃)₃] with L ³ yielded three fractions. Fraction 1 yielded crystals (3) composed of three crystallographically independent species incorporating cations of type [Co(L ³ )Cl]²⁺ with very similar structures; in each case the macrocyclic ring nitrogens of L ³ are bound to the Co(III) in an asymmetric cis-fashion. Fraction 2 yielded the trans-III octahedral cationic complex (4) incorporating L ³ in its protonated form. The Co(III) complex (5) from fraction 3 shows a different coordination arrangement to the products from fractions 1 or 2. The macrocyclic ring coordinates in its trans-III form, but the axial sites in this case are occupied by the pendent-NH₂ group and a Cl^? ligand.     

Comparative investigation of the copper(II) complexes of (R)-, (S)- and (R,S)-1-phenyl-N,N-bis(pyridine-3-ylmethyl)ethanamine along with the related complex of (R,S)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine. Synthetic, magnetic, and structural studies

The interaction of the enantiopure (R)- and (S)-1-phenyl-N,N-bis(pyridine-3- ylmethyl)ethanamine ligands, R-L ¹ and S-L ¹ , with copper(II) chloride followed by addition of hexafluorophosphate resulted in the isolation of the corresponding enantiomeric complexes [Cu(R-L ¹ )Cl](PF₆) (1), [Cu(S-L ¹ )Cl](PF₆) (2) and [Cu(S-L ¹ )Cl](PF₆)??0.5Et₂O (3), in which dimerization occurs through two long Cu??????Cl interactions, the ??-chloro bridges being thus strongly asymmetric. The organic ligand is bound to the metal centre via its N₃-donor dipyridylmethylamine fragment in a planar fashion, such that each copper centre is in a square planar environment (or distorted square pyramidal with a long axial bond length if the additional interaction is considered). When R,S-L ¹ was employed in a parallel synthesis, the similar racemic complex [Cu(R,S-L ¹ )Cl](PF₆)??0.5MeOH (4) was obtained, in which the L ¹ ligands in each dimeric unit have opposite hands. In contrast to the complexes of L ¹ , the reaction of Cu(II) chloride with the related ligand, (R)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine (R-L ² ), yielded the mononuclear complex [Cu(R,S-L ² )Cl₂] (5), displaying a distorted square pyramidal coordination geometry. The structure of this product along with its corresponding circular dichroism spectrum revealed that racemisation of the starting R-L ² ligand has occurred under the relatively mild (basic) conditions employed for the synthesis. A temperature-dependent magnetic studies of the complexes 1, 2 and 5 indicate that a week ferromagnetic interaction is operative in each dicopper core in 1 and 2 with 2J?=?1.2?cm^?1. On the other hand, a week antiferromagnetic intermolecular interaction is operative for 5.     

Synthesis and characterization of a series of chiral NHC–Pd complexes derived from l-phenylalanine

The synthesis of a series of chiral Pd(L)PyBr₂ (3a–3e) and Pd(L)PyCl₂ (4d and 4e) complexes from l-phenylalanine is presented (L = (S)-3-allyl-4-benzyl-1-(2,6-diisopropylphenyl)-imidazolin-2-ylidene (a), (S)-4-benzyl-1-(2,6-diisopropylphenyl)-3-(naphthalen-2-ylmethyl)imidazolin-2-ylidene (b), (S)-4-benzyl-3-(biphenyl-4-ylmethyl)-1-(2,6-diisopropylphenyl)imidazolin-2-ylidene (c), (S)-4-benzyl-1-(2,6-diisopropylphenyl)-3-(naphthalen-1-ylmethyl)imidazolin-2-ylidene (d) or (S)-4-benzyl-1-(2,6-diisopropylphenyl)-3-(2,4,6-trimethylbenzyl)imidazolin-2-ylidene (e). The complexes were characterized by physicochemical and spectroscopic methods, and the X-ray crystal structures of 3a–3c and 4d are reported. In each case, there is a slightly distorted square-planar geometry around palladium, which is surrounded by imidazolylidene, two trans halide ligands and a pyridine ligand. There are π–π stacking interactions in the crystal structures of these complexes. Complex 3a showed good catalytic activity in the Cu-free Sonogashira coupling reaction under aerobic conditions.     

Chinolizine und Indolizine,XIII. Acyl-2-hydroxy-4-chinolizinone

The reaction of 2-picolylketones (1 a, b) with reactive trichlorophenyl malonates (2 a–f) leads to 1-acyl-2-hydroxy-4-quinoliziones (3 a–i) which can be easily deacylated by boiling hydrochloric acid yielding 4-quinolizinones4 a–f. The 3-acetyl-2-hydroxy-4-quinolizinones6 and8 are obtained byKlosa-Ziegler acylation of4 a and7, respectively. The reaction of the acetyl compound3 a with acetic anhydride yields the 2-pyrone derivative9, whereas the propionyl derivative3 g yields the 4-pyrone10 under the same conditions. Nitration of3 e does not give the 1-nitro derivative12 but rather the 1,3-dinitro compound11.