Nucleophilic subsitution at silicon: Synthesis of sterically-hindered bis(2,6-di-t-butylaryloxy)silanes

The reaction of the monomethylsilane (8a) with two equivalents of the 4-(carboalkoxy)-2,6-di-t-butyl-substituted phenol (7b) in toulene using triethylamine as an acid acceptor gave the bis(aryloxy) adduct (9a). The analogus reaction of the dimethylsilane (8b) with sodium 2,6-di-t-butyl-4-(methoxycarboxyl)-phenolate (7a) gave only the monosubstitution product (10a). The reaction of the corresponding phenolate (7e) with 8b gave a mixture of 7a, 10a, and bis-adduct (9b), whereas, in the presence of 15-crown-5, the bis-adduct 9b was obtained. The bis-adducts 9c–e were prepared in an analogous manner. The reaction of n-hexyl 3,5-di-t-butyl-4-hydoxylbenzoate (7h) with the diphenylsilane (8c) gave only the monosubstitution product 12, while forcing conditions gave, unexpectedly, the methyl ether 13. The reaction of 4-(carboalkoxyethyl)-2,6-di-t-butylphenol (16a) with 8a gave the bis adduct. The reaction of 16a with 8b in THF, without a crown ether, gave a low yield of the monosubstitution product. The bis-adducts 17b–c were obtained by the reaction of 8b with the corresponding phenolates (16a–b) in tetraglyme. Compound 17b was also obtained by the reaction of 8b with 16a in THF with a crown ether. These results are discussed in terms of charge dispersal in the phenolate ion and the corresponding effect upon both ion-pairing and aggregation in solution.     

Synthese und reaktivität von silicium-übergangsmetall-komplexen: XVIII. Trihydrosilylkomplexe des eisens: Darstellung und metallierung mit dicobaltoctacarbonyl

The reaction of the silyl complex Cp(CO)₂FeSiH₃ (1) with various donors under photochemical conditions leads to the formation of Cp(CO)(L)FeSiH₃ (2a-2c) and Cp(L)₂FeSiH₃ (3a, 3b) (L = MeNC, t-BuNC, Me₃P) via stepwise CO-substitution. 2a,2b are transformed by Co₂(CO)₈ to the complexes μ₂-[Cp(CO)-(RNC)FeSiH] [μ²-(CO)] Co₂(CO)₆ (3a,3b), the first complexes with a hydrogen substituted ferrio-silanediyl unit bridging two cobalt atoms.     

Synthetic and structural studies of [6]-, [7]- and [10]metacyclophanes

A new preparative sequence from 2,3-polymethylene-2-cyclopentenone 5 to 2,6-polymethylenebromobenzenes 3 (n = 6, 7, 10) and 2,6-polymethylenephenyllithiums 6 has been found. The reaction of 6 with various electrophiles produces a number of new compounds to disclose the unique reactivity of the aryl C-Li moiety surrounded by the polymethylene chain. Photolysis of 3a and 3b provides transannular products 8, 10 and 11, all arising from the proximity between the aromatic bromine and the aliphatic hydrogen intraannularly opposed to be removed as HBr. Spectrometric study gives quantitative data of the dependence of the molecular geometry upon the chain length and the aromatic substituents. The energy barriers ΔG_c^≠ of the conformational flipping are 17·4 kcal/mol (T_c 76·5°) for [6]metacyclophane (7a), 11·5 kcal/mol (T_c ?28°) for [7]metacyclophane (7b), ·8 kcal/mol for [10]metacyclophane (7c). The lower-energy process of the aliphatic chain in [6]metacyclophane derivatives is the pseudorotation with substituent-dependent barrier ΔG_c^≠ 11·1 kcal/mol (T_c ?31·5°) for 7a, 12·4 kcal/mol (T_c ?4·5°) for 3a and 12·7 kcal/mol (T_c 1·0°) for 12a. The rather large rotational barrier is attributed to the compressed structure of each system. The benzene ring distortion of the cyclophanes is deduced from the bathochromic shift of the B-band and the diamagnetic shift of the benzene proton signals in the PMR.     

Synthesis,antimicrobial and anticancer activities of some new N-methylsulphonyl and N-benzenesulphonyl-3-indolyl heterocycles: 1st Cancer Update

A series of 1-(N-methyl 2a–c and N-benzenesulphonyl-1H-indol-3-yl)-3-aryl-prop-2-ene-1-ones 3a–c were prepared and allowed to react with urea, thiourea or guanidine and gave the pyrimidine derivatives 4a–c to 9a–c. Base catalyzed reaction of 2a–c or 3a–c with ethyl acetoacetate gave cyclohexanone derivatives 10a–c and 11a–c, respectively. Reaction of the latter compounds with hydrazine hydrate afforded indazole derivatives 12a–c and 13a–c, respectively. On the other hand, condensation of 2c or 3c with some hydrazine derivatives namely, hydrazine hydrate, acetyl hydrazine, phenyl hydrazine and benzyl hydrazine hydrochloride gave pyrazole derivatives 14a,b-17a,b, respectively. Moreover, reaction of 2c or 3c with hydroxyl amine hydrochloride gave isoxazole derivatives 18a,b. The newly synthesized compounds were tested for their antimicrobial activity and showed that, compounds 14a, 14b, 15a and 15b were found to be the most active ones of all the tested compounds toward Salmonella typhimurium (ATCC 14,028) compared to the reference drug chloramphenicol. Eighteen new compounds namely, pyrimidin-2(1H)-ones 4a–c and 5a–c, pyrimidin-2(1H)-thiones 6a–c and 7a–c and pyrimidin-2-amines 8a–c and 9a–c were tested for their in vitro cytotoxicity against human liver carcinoma (HEPG2), human breast cancer (MCF7) and human colon cancer (HCT-116) cell lines and showed that, compounds 4c, 5c, 6c, 8c and 9c were found to be the highly active compounds compared to the reference drug doxorubicin.     

Nitrileketenimine tautomerism in substituted alkylidene malononitriles and alkylidene cyanoacetates: A characteristic UV absorption band

Several alkylidene malononitriles (1b,1d,1e,2b and4b) and alkylidene cyanoacetates (1a,2a and4a) studied exhibit a long wavelength UV absorption band around 355 nm which shows a hyperchromic effect in the presence of ethanolic alkali. This band has been assigned to the ketenimine tautomer (5). Addition of water to1b,1e and2b gives the corresponding pyridine diols (7a,7b and8a) respectively. Similarly, addition of ethanol to1e and2b gave the corresponding ethoxypyridine derivatives (7c and8b). Mechanism of formation of these compounds is discussed. Structures, as well as mechanism of formation of1c,7c and10 obtained from1b,1e and2b respectively on standing at room temperature are also discussed.     

Ni(II) and Cu(II) complexes of phenoxy-ketimine ligands: Synthesis,structures and their utility in bulk ring-opening polymerization (ROP) of l-lactide

Synthetic, structural and catalysis studies of Ni(II) and Cu(II) complexes of a series of phenoxy-ketimine ligands with controlled variations of sterics, namely 2-[1-(2,6-diethylphenylimino)ethyl]phenol (1a), 2-[1-(2,6-dimethylphenylimino)ethyl]phenol (1b) and 2-[1-(2-methylphenylimino)ethyl]phenol (1c), are reported. Specifically, the ligands 1a, 1b and 1c were synthesized by the TiCl₄ mediated condensation reactions of the respective anilines with o-hydroxyacetophenone in 21–23% yield. The nickel complexes, {2-[1-(2,6-diethylphenylimino)ethyl]phenoxy}₂Ni(II) (2a) and {2-[1-(2,6-dimethylphenylimino)ethyl]phenoxy}₂Ni(II) (2b), were synthesized by the reaction of the respective ligands 1a and 1b with Ni(OAc)₂ · 4H₂O in the presence of NEt₃ as a base in 71–75% yield. The copper complexes, {2-[1-(2,6-diethylphenylimino)ethyl]phenoxy}₂Cu(II) (3a), {2-[1-(2,6-dimethylphenylimino)ethyl]phenoxy}₂Cu(II) (3b) and {2-[1-(2-methylphenylimino)ethyl]phenoxy}₂Cu(II) (3c) were synthesized analogously by the reactions of the ligands 1a, 1b and 1c with Cu(OAc)₂ · H₂O in 70–87% yield. The molecular structures of the nickel and copper complexes 2a, 2b, 3a, 3b and 3c have been determined by X-ray diffraction studies. Structural comparisons revealed that the nickel centers in 2a and 2b are in square planar geometries while the geometry around the copper varied from being square planar in 3a and 3c to distorted square planar in 3b. The catalysis studies revealed that while the copper complexes 3a, 3b and 3c efficiently catalyze ring-opening polymerization (ROP) of l-lactide at elevated temperatures under solvent-free melt conditions, producing polylactide polymers of moderate molecular weights with narrow molecular weight distributions, the nickel counterparts 2a and 2b failed to yield the polylactide polymer.     

Molecular structure of two dicyclopentadienylmolybdenum derivatives containing a four-membered ring [Mo(η5-C5H5)2(2-NHNC5H4)][PF6] and [Mo(η5C5H5)2(2-ONC5H4)][PF6]

The structure of the new compound [Mo(η⁵-C₅H₅)₂(2-NHNC₅H₄)][PF₆] (1) has been determined. The crystals are orthorhombic, space group Pca2₁ with a 20.807(1), b 8.0030(8), c 10.056(3) Å, V 1674.5 ų, Z = 4. The structure of [Mo(η⁵-C₅H₅)₂(2-ONC₅H₄)][PF₆] (2) has also been determined. The crystals are orthorhombic, space group Pnma with a 12.727(3), b 10.174(2), c 12.918(1) Å, V 1672.8 ų, Z = 4. The structures were solved by Patterson and difference electron density syntheses and refined by least-squares to R of 0.028 for 1287 reflections for 1 and 0.059 for 1178 reflections for 2.Although not isostructural the two cationic complexes have equivalent geometries with the normal bent bismetallocene structure. For 1 the MoN bond lengths are 2.160(8) and 2.142(9) Å, with a NMoN bond angle of 59.8(3)°, whereas for 2 MoO is 2.142(10), MoN is 2.138(11) Å, the NMoO angle is 61.2(4)°. These parameters are discussed and compared with the corresponding data for similar biscyclopentadienyl complexes of molybdenum(IV). Extended Hückel molecular orbital calculations have been carried out to throw light on the nature of the bonding between the metal and the bidentate ligand.     

Organized multilayers of polydiacetylenes prepared by electrostatic self-assembly

New types of polydiacetylene multilayer are presented. The first type is based on electrostatic self-organization of diacetylene bolaamphiphiles and polyelectrolytes on a charged substrate followed by subsequent ultraviolet (UV) polymerization. The second type is prepared by direct adsorption of a water soluble polydiacetylene and a polyelectrolyte in alternating sequence. The monomeric diacetylenes are of general formula X(CH₂)₉CCC C(CH₂)₉X, with X being a sulfate (1a), phosphate (2) or pyridinium (3) head group. The polydiacetylene (1b) chosen for the multilayer is obtained by γ irradiation of the corresponding diacetylene monomer 1a. It is found that all diacetylene derivatives are well suited for building up self-assembled multilayers and that two of the monomers (1a, 2) can be polymerized on the substrate, while 3 is photo-inactive. The morphology of the multilayers is studied by scanning force microscopy and discussed. The smoothest surface topology is found for multilayers built up from the polydiacetylene 1b and a cationic polyelectrolyte in alternating sequence, while the largest unevenness is found when the anionic diacetylene 1a is alternatingly adsorbed with the cationic bolaamphiphile 3 followed by subsequent UV polymerization on the substrate.     

Metal complexes of anionic 3-borane-1-alkylimidazol-2-ylidene derivatives

Addition of BH₃·thf to 1-alkylimidazoles (alkyl=methyl, butyl) and 1-methylbenzimidazole leads to BH₃ adducts, which are deprotonated by BuLi to yield the organolithium compounds (L)Li⁺(1b–d)⁻. In the solid state (thf)Li⁺1b⁻ is dimeric. The acyl–iron complexes (thf)₃Li⁺(3b,d)⁻ are formed from (thf)Li⁺(1b,d)⁻ and Fe(CO)₅. (L)Li⁺(1a–c)⁻ react with [CpFe(CO)₂X], however, the only complex obtained is [CpFe(CO)₂1a] (5a). The analogous reaction of (L)Li⁺1a⁻ with the pentadienyl complex [(C₇H₁₁)Fe(CO)₂Br] yields the corresponding iron compound 6a. Their compositions follow from spectroscopic data. Treatment of Cp₂TiCl with (L)Li⁺1a⁻ leads to [Cp₂Ti1a] (7a), which could not be oxidized with PbCl₂ to give the corresponding Ti(IV) complex. The compounds [Li(py)₄]⁺9a⁻ and [Li(L)₄]⁺(10b–d)⁻ are obtained when (L)Li⁺1⁻ are reacted with VCl₃ and ScCl₃. The X-ray structure analysis of the vanadium complex reveals a distorted tetrahedron of the anion [V(1a)₄]⁻ with two smaller and four larger CVC angles. The scandium compound [Li(dme)₂⁺10c⁻] has a different structure: the distorted tetrahedron of the anion [Sc(1c)₄]⁻ contains two larger (140.2 and 142.9°) and four smaller CScC angles (93.9–98.7°). This arrangement allows the formation of four bridging BHSc 3c,2e bonds to give an eight-fold coordination. The anion 10c⁻ is formally a 16e complex.     

Synthesis and characterization of novel trifluoromethyl-containing alcohols with Ruppert's reagent

Synthesis and characterization of novel new trifluoromethyl-containing alcohols using Ruppert's reagent [(trimethyl)trifluoromethylsilane] (1) are reported. The reactions of 1 with various ketones and aldehydes, such as tetraphenylcyclopentadienone (2a), 9,10-anthraquinone (2b), pyrenaldehyde (2c), 2,6-dimethyl-para-anisaldehyde (2d), and 2,3(methylenedioxy)benzaldehyde (2e) in the presence of a catalytic amount of tetrabutylammonium fluoride in THF led to the formation of the corresponding trifluoromethylated silyl ether derivatives 3a–e in almost quantitative yields. Acid hydrolysis of 3a–e gave the desired trifluoromethylated alcohol derivatives (4a–e) in excellent isolated yields. Compounds were characterized by IR, NMR (¹H, ¹⁹F, ¹³C NMR), GCMS, and elemental analysis. Single crystal X-ray structures of 4a and 4b support the proposed products.     

Allylstannation of α-, β- and γ-diketones mediated by allylbutyltin halides: Bu2(CH2=CHCH2) SnCl and Bu(CH2 =CHCH2) SnCl2

Butane-2,3- (1a), pentane-2,4- (1b) and hexane-2,5-dione (1c) react with Bu₂(CH₂=CHCH₂)SnCl in the presence of water to give monoallylated keto-ols (2a, 2b) and/or diallylated diols (3a, 3b, 3c), this depending upon the employed molar ratio [diketone]/[allyltin chloride]. Bu(CH₂=CHCH₂)SnCl₂ reacts with neat 1c in a one-pot synthesis to give mixtures of heterocyclic compounds: 2,5-diallyl-2,5-dimethyltetrahydrofuran (4), and 3-chloro-1,5-dimethyl-8-oxabicyclo [3,2,1] octane (5). Compound 4 is also obtained in high yield from the corresponding diol 3c by cyclodehydration promoted by RSnCl₃ (R = Me and Bu).     

Syntheses and pharmacological characterization of achiral and chiral enantiopure C/Si/Ge-analogous derivatives of the muscarinic antagonist cycrimine: a study on C/Si/Ge bioisosterism

The C/Si/Ge-analogous compounds rac-Ph(c-C₅H₉)El(CH₂OH)CH₂CH₂NR₂ (NR₂=piperidino; El=C, rac-3a; El=Si, rac-3b; El=Ge, rac-3c) and (c-C₅H₉)₂El(CH₂OH)CH₂CH₂NR₂ (NR₂=piperidino; El=C, 5a; El=Si, 5b; El=Ge, 5c) were prepared in multi-step syntheses. The (R)- and (S)-enantiomers of 3a–c were obtained by resolution of the respective racemates using the antipodes of O,O′-dibenzoyltartaric acid (resolution of rac-3a), O,O′-di-p-toluoyltartaric acid (resolution of rac-3b), or 1,1′-binaphthyl-2,2′-diyl hydrogen phosphate (resolution of rac-3c). The enantiomeric purities of (R)-3a–c and (S)-3a–c were ≥98% ee (determined by ¹H-NMR spectroscopy using a chiral solvating agent). Reaction of rac-3a–c, (R)-3a–c, (S)-3a–c, and 5a–c with methyl iodide gave the corresponding methylammonium iodides rac-4a–c, (R)-4a–c, (S)-4a–c, and 6a–c (3a–c→4a–c; 5a–c→6a–c). The absolute configuration of (S)-3a was determined by a single-crystal X-ray diffraction analysis of its (R,R)-O,O′-dibenzoyltartrate. The absolute configurations of the silicon analog (R)-4b and germanium analog (R)-4c were also determined by single-crystal X-ray diffraction. The chiroptical properties of the (R)- and (S)-enantiomers of 3a–c, 3a–c·HCl, and 4a–c were studied by ORD measurements. In addition, the C/Si/Ge analogs (R)-3a–c, (S)-3a–c, (R)-4a–c, (S)-4a–c, 5a–c, and 6a–c were studied for their affinities at recombinant human muscarinic M₁, M₂, M₃, M₄, and M₅ receptors stably expressed in CHO-K1 cells (radioligand binding experiments with [³H]N-methylscopolamine as the radioligand). For reasons of comparison, the known C/Si/Ge analogs Ph₂El(CH₂OH)CH₂CH₂NR₂ (NR₂=piperidino; El=C, 7a; El=Si, 7b; El=Ge, 7c) and the corresponding methylammonium iodides 8a–c were included in these studies. According to these experiments, all the C/Si/Ge analogs behaved as simple competitive antagonists at M₁–M₅ receptors. The receptor subtype affinities of the individual carbon, silicon, and germanium analogs 3a–8a, 3b–8b, and 3c–8c were similar, indicating a strongly pronounced C/Si/Ge bioisosterism. The (R)-enantiomers (eutomers) of 3a–c and 4a–c exhibited higher affinities (up to 22.4 fold) for M₁–M₅ receptors than their corresponding (S)-antipodes (distomers), the stereoselectivity ratios being higher at M₁, M₃, M₄, and M₅ than at M₂ receptors, and higher for the methylammonium compounds (4a–c) than for the amines (3a–c). With a few exceptions, compounds 5a–c, 6a–c, 7a–c, and 8a–c displayed lower affinities for M₁–M₅ receptors than the related (R)-enantiomers of 3a–c and 4a–c. The stereoselective interaction of the enantiomers of 3a–c and 4a–c with M₁–M₅ receptors is best explained in terms of opposite binding of the phenyl and cyclopentyl ring of the (R)- and (S)-enantiomers. The highest receptor subtype selectivity was observed for the germanium compound (R)-4c at M₁/M₂ receptors (12.9-fold).     

Chelating diamide complexes of titanium: new catalyst precursors for the highly active and living polymerization of α-olefins

The reaction of RHN(CH₂)₃NHR (1a,b) (a, R=2,6-ⁱPr₂C₆H₃; b, R=2,6-Me₂C₆H₃) with 2 equiv of BuLi followed by 2 equiv of ClSiMe₃ yields the silylated diamines R(Me₃Si)N(CH₂)₃N(SiMe₃)R (3a,b). The reaction of 3a,b with TiCl₄ yields the dichloride complexes [RN(CH₂)₃NR]TiCl₂ (4a,b) and two equiv of ClSiMe₃. An X-ray study of 4a (P2₁/n, a=9.771(1) Å, b=14.189(1) Å, c=21.081(2) Å, β=96.27(1)°, V=2905.2(5) ų, Z=4, T=25°C, R=0.0701, R_w=0.1495) revealed a distorted tetrahedral geometry about titanium with the aryl groups lying perpendicular to the TiN₂-plane. Compounds 4a,b react with 2 equiv of MeMgBr to give the dimethyl derivatives [RN(CH₂)₃NR]TiMe₂ (5a,b). An X-ray study of 5b (P2₁2₁2₁, a=8.0955(10) Å, b=15.288(4) Å, c=16.909(3) Å, V=2092.8(7) ų, Z=4, T=23°C, R=0.0759, R_w=0.1458) again revealed a distorted tetrahedral geometry about titanium with titanium–methyl bond lengths of 2.100(9) Å and 2.077(9) Å. These titanium dimethyl complexes are active catalysts for the polymerization of 1-hexene, when activated with methylaluminoxane (MAO). Activities up to 350,000 g of poly(1-hexene)/mmol catalyst·h were obtained in neat 1-hexene. These systems actively engage in chain transfer to aluminum. Equimolar amounts of 5a or 5b and B(C₆F₅)₃ catalyze the living aspecific polymerization 1-hexene. Polydispersities (M_w/M_n) as low as 1.05 were measured. Highly active living systems are obtained when 5a is activated with {Ph₃C}⁺[B(C₆F₅)₄]⁻. A primary insertion mode (1,2 insertion) has been assigned based on both the initiation of the polymer chain and its purposeful termination with iodine.     

Synthese und strukturuntersuchungen von zwei stannylwolframpentacarbonylen R2Sn-W(CO)5 (R = (o-dimethylaminomethyl)phenyl bzw. (o-diphenylphosphinomethyl)phenyl)

The compounds [o-C₆-H₄CH₂E]₂Sn-W(CO)₅, (E = NMe₂ (1) or PPh₂ (2)) have been prepared by reaction of o-LiC₆H₄CH₂E with pentacarbonyltungsten tin(II) chloride (CO)₅WSnCl₂. The complexes were characterized by ¹³C, ³¹P, and ¹¹⁹Sn NMR spectroscopy and by X-ray diffraction analyses. 1 crystallizes monoclinically in the space group C/c (no. 15) with a 1310.2(4), b 1552.1(4), c 1202.9(4) pm, β 90.11(4)°, and Z = 4. 2 crystallizes monoclinically in the space goup P2₁/n (no. 14) with a 2108.1(4), b 1707.7(4), c 1283.7(3) pm, β 97.47(2)° and Z = 4. The structures were refined to final R values of 0.029 and 0.039, respectively.The SnW bond distances of 274.9 and 276.2 pm are very similar in both complexes. The Sn atoms are penta-coordinated by 2C, 2N and W in 1 and by 2C, 2P and W in 2. The penta-coordination comprises one SnW and two SnC single bonds, and either a SnN (in 1) or a SnP bond (in 2) of bond order 0.45. In the stannyl group of 1 the SnN bond distances both are identical by symmetry (256.4 pm), whereas the two SnP bond lengths of 2 differ to some extent (283.1 and 301.2 pm).     

The total synthesis and anti-fertility activity of 6-silasteroids

4,4-Dimethyl-6-methoxy-4-sila-1-tetralone (2) was prepared by a modified literature procedure and converted to 3-methoxy-6,6-dimethyl-6-silaestra-1,3,5(10),8,14-pentaen-17β-yl acetate (5c). Catalytic hydrogenation of 5c gave 3-methoxy-6,6-dimethyl-6-silaestra-1,3,5(10),8-tetraen-17β-yl acetate (6b), and its 14-iso- and Δ^{1,3,5(10),8(14)} isomers, the proportions varying with the catalyst and solvent. Reduction of 6b with lithium-liquid ammonia, and O-demethylation, gave 6,6-dimethyl-6-silaestradiol (8b). Reduction of the 3-methyl ether of 8b with lithium-liquid ammonia-t-butanol and hydrolysis afforded 3-keto-6,6-dimethyl-6-silaestr-1(10)-en-17β-ol (15), which was catalytically reduced to its 1,10α-dihydro derivative 17. The 5,6 SiC bond of 8b, 15 and their derivatives was cleaved by boron tribromide, aq. ethanolic hydrogen fluoride, and other reagents, providing a series of 5,6-seco-6,6-dimethyl-6-silasteroids. X-ray crystallographic analysis of 17 and the 17α-ethynyl derivative of 15 confirmed the stereochemical assignments. None of the compounds which were subjected to uterotropic, anti-uterotropic, or post-coital assays, showed significant activity. A partially completed synthesis of 6-silaestradiol (21a) is described.     

4-Ferrocenylpyridine- and 4-Ferrocenyl-3-ferrocenylmethyl-3,4-dihydropyridine-3,5-dicarbonitriles: Multi-Component Synthesis, Structures and Electrochemistry

The reactions of 2-cyano-3-ferrocenylacrylonitrile (1) with malononitrile (2) in a MeOH/H₂O or 2-PrOH/H₂O medium in the presence of Na₂CO₃ afforded 6-alkoxy-2-amino-4-ferrocenylpyridine-3,5-dicarbonitriles 3a,b (multi-component condensation) and 6-alkoxy-2-amino-4-ferrocenyl-3-ferrocenylmethyl-3,4-dihydropyridine-3,5-dicarbonitriles 4a,b (multi-component cyclodimerization). Analogous reactions of 1 with 2 in an MeOH/H₂O medium in the presence of NaOH, piperidine, or morpholine gave compounds 3a, 4a and 2-amino-4-ferrocenyl-6-hydroxy-, 6-piperidino- and 6-morpholinopyridine-3,5-dicarbonitriles 3c-e, respectively. The structures of the compounds 3b, 4a and 4b were established by the spectroscopic data and X-ray diffraction analysis. The electrochemical behaviour of compounds 3b, 3d and 4b was investigated by means of cyclic voltammetry.     

The chemistry of N-benzylidene-1,4-phenylenediamine palladacycles: The crystal and molecular structure of the first tetranuclear palladacycle with bridging Ph2PCH2PPh2 ligands

The reaction of the tetranuclear halide-bridged complexes 1?2(a?d) with Ph₂PCH₂PPh₂ (dppm) or Ph₂PC(CH₂)PPh₂ (vdpp) in 1:2 molar ratio and NH₄PF₆ afforded the novel tetarnuclear palladacycles 3?6 (a, c, d) as 1:2 electrolytes with bridging diphosphine and halogen ligands. The structure of 4a has been determined by X-ray diffraction analysis, and represents the first example of a tetranuclear palladacycle with bridging dppm and halogen ligands. Reaction of 1?2(a?d) with (Ph₂PCH₂CH₂)₂PPh (triphos) in 1:2 molar ratio gave 7(a?d) bearing two pentacoordinated palladium atoms. The structure of 7a, as determined by X-ray diffraction analysis, shows the distorted square pyramidal geometry around the metal centers. Treatment of 1?2(a?d) with dppm, vdpp or Ph₂PN(Me)PPh₂ (dppma) in 1:4 molar ratio gave the dinuclear palladacycles 8?10(a?d) with a chelating diphosphine ligand at each metal center; further treatment of 9(a?c) with the nucleophiles pyrrolidine, piperidine, morpholine or 4-methyl-piperidine gave the Michael addition derivatives 11?12(a?c), 13b, 13c and 14c, promoted by the withdrawing effect of the palladacycle which activates the CCH₂ double bond.     

Distorted tetrahedral copper(I)′complexes of 2,2′bi-4,5-dihydrothiazine and 2,2′-bi-2-thiazoline

The copper(I) complexes [Cu(btz)₂](BPh]₄(I) and [Cu₂(bt)₄][ClO₄]₂ (II) have been prepared (btz = 2,2′-bi-4,5-dihydrothiazine and bt = 2,2′-bi-2-thiazoline). Crystals of (I) are orthorhombic with a = 10.927(8), b = 11.743(8), c = 15.000(6) A, Z = 2, spacegroup P2₁2₁2. Crystals of (II) are monoclinic with a = 21.928(11), b = 11.925(8), c = 14.716(11) A, β = 103.6(1), Z = 8, spacegroup C2/c. 2121 and 2204 independent reflections have been measured on a diffractometer and the structures refined R 0.061 to R 0.063 respectively. In the cation of (I) the two btz ligands are coordinated via the α-di-imine groups (Cu-N 2.010(6), 2.024(6)Å). The resulting CuN₄ coordination geometry is a flattened tetrahedron with a dihedral angle of 68.9° between the two “CuN₂” planes. It is suggested that this distortion is an intrinsic property of the molecule associated with metal-to-ligand d_π-p_π* charge transfer rather than a consequence of lattice packing effects. In the dimeric cation (II), each copper(I) ion is bonded to the α-di-imine group of one bt molecule (A) but with appreciably different CuN bond lengths (2.277(6), 1.999(5)Å), to one nitrogen atom of a second ligand molecule (B) in the trans configuration (CuN 1.961(5)Å) and to one sulphur atom (CuS 2.428(2)Å) of a third ligand molecule (C). The coordination geometry is a very distorted tetrahedron if a very weak interaction (Cu…S 3.039(2)Å) with a sulphur atom of ligand B is discounted. It is suggested that the different structure arise from the different “bites” of the two ligands.     

Reaction of N-alkoxycarbonylaziridines with nitriles

The acid catalysed reaction of acetonitrile or benzonitrile with N-alkoxycarbonylaziridines, 1a and 1b yields the corresponding 1-alkoxycarbonyl-2-imidazolines, 2ax, 2ay, and 2bx. The imidazolines obtained by the reaction of N-ethoxycarbonyl-2,3-tetramethyleneaziridine (1c) with acetonitrileor benzonitrile are labile and are readily hydrolysed to trans-cyclohexane-1,2-diamine derivatives (3cx or 3cy). The nitrile-addition supposedly proceeds S_N2 type CN bond cleavage and CN bond formation.     

Studies on ketene and its derivatives. CXI . Photoreaction of diketene with 2(1H)-quinolone derivatives

Photoreaction of diketene with 4-methyl-2(1H)-quinolone and 1,4-dimethyl-2(1H)-quinolone gave 2R*,2aR*,SbR*- and 2R*,2aS*8bS*-8b-methyl-3-oxo-1,2,2a,3,4,8b-hexahydrocyclobuta[c]quinoline-2-spiro-2′-(oxetan)-4′-one ( 6a and 6b ), and their 4-methyl derivatives 7a and 7b , respectively. Thermolysis of compounds 6 and 7 afforded 2aR*,8bS*-8b-methyl-2-methylene-3-oxo-1,2,2a,3,4,8b-hexahydrocyclobuta[c]quinoline ( 8 ) and its 4-methyl derivatives 9 , respectively. Similarly, photolysis of diketene and 4-acetoxy-2(1H)-quinolone gave 1R*,2aS*,8bS*- and 1R*,2aR*,8bR*-8b-acetoxy-3-oxo-1,2,2a,3,4,8b-hexahydrocyclobuta[c]-quinoline ( 11a and 11b ). Alcoholysis of compounds 11a and 11b with hydrogen chloride in methanol gave 1-hydroxy-1-(methoxycarbonyl)methylcyclobuta[c]quinoline derivative 12 and 13 which were transformed to 4-acetyl-3-methyl-2(1H)-quinolone ( 15 ) by further alcoholysis. Photoreaction of diketene with 2(1H)-quinolone derivatives gave the corresponding cyclobuta[c]quinoline spirooxetanone derivatives 18 and 23 , which, by thermolysis, were transformed to 2-methylenecyclobuta[c]quinoline 23 and 25 , respectively.