3-Ferrocenyl-1-methyl- and 1-ferrocenyl-3-methylcyclopropenes

Dehydrobromination of isomeric 3-bromo-1-ferrocenyl-2-methylcyclopropanes afforded 3-ferrocenyl-1-methyl- and 1-ferrocenyl-3-methylcyclopropenes. These undergo smooth opening of the three-membered ring to give 1- and 2-ferrocenylbuta-1,3-dienes and 1- and 2-methyl-1H-cyclopentaferrocenes; with 1,3-diphenylisobenzofuran they give the classical Diels-Alder adducts.     

Synthesis of chiral 1-ferrocenylaldols and 1-ferrocenyl-1,3-diols via asymmetric reductions

The asymmetric transfer hydrogenation promoted by the (R,R)-(Ts-DPEN)–Ru complex of some 1-ferrocenyl-1,3-diketones was investigated and in all the cases only the carbonyl group distant to the metallocene moiety was reduced with variable selectivity depending on the C-3 substituent. The CBS-catalyzed reduction of 1-ferrocenyl-β-hydroxy-1-ketones, previously protected as acetates, was also found effective, giving both the corresponding syn- and anti-1,3-diols in satisfactory enantiomeric purity.     

Synthesis and some chemical transformations of 3-ferrocenyl-3-phenylcyclopropene

Crystalline 3-ferrocenyl-3-phenylcyclopropene was obtained by dehydrobromination of 2-bromo-l-ferrocenyl-l-phenylcyclopropane with potassiumtert-butoxide in dimethyl sulfoxide. The compound synthesized undergoes catalytic hydrogenation to l-ferrocenyl-I-phenylcyclopropane, reacts with 1,3-diphenylisobenzofuran to give the expected product of stereospecific [4+2[-cycloaddition and 3-ferrocenylindene, and also undegoes opening of the small ring on treatment with superacids to give 3-ferrocenylindene as the major product. The data of single crystal X-ray diffraction analysis of 1-ferrocenyl-l-phenylcyclopropane and the diene adduct of 3-ferrocenyl-3-phenylcyclopropene with 1,3-diphenylisobenzofuran are given.     

Synthesis and properties of 5-ferrocenyl-1H-pyrazole-3-carbaldehydes

New ferrocene derivatives - ethyl esters of 1-aryl-5-ferrocenyl-1H-pyrazole-3-carboxylic acids were synthesized. The corresponding aldehydes were obtained from acid esters in two steps. The reductive amination reaction of 5-ferrocenyl-1-phenyl-1H-pyrazole-3-carbaldehyde was studied. Several of these compounds were investigated by cyclic voltammetry. All of them exhibited a reversible one-electron oxidation-reduction wave owing to the ferrocene-ferricinium redox couple with a positive shift (0.51-0.69 V) compared with that of ferrocene (0.46 V). The X-ray crystal structure of the ethyl ether 1-(3-chloro-2-fluorophenyl)-5-ferrocenyl-1H-pyrazole-3-carboxylic acid is also presented.     

Asymmetric cyclopalladation of 6-ferrocenyl-2,2′-bipyridine and 2-ferrocenyl-1,10-phenanthroline

Cyclopalladation of 6-ferrocenyl-2,2′-bipyridine and 2-ferrocenyl-1,10-phenanthroline in the presence of the N-acylamino acid salt as the asymmetric catalyst was performed. Some reactions of the resulting bicyclic palladium derivatives with tridentate (N,N,C) ligands were studied. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1039–1041, May, 2007.     

Crystal structures of methyl and benzyl 5-ferrocenyl-3,5-dimethyl-2-pyrazoline-1-dithiocarboxylate

Reactions of E-4-ferrocenylpent-3-en-2-one with S-methyldithiocarbazate or S-benzyldithiocarbazate result in the formation of methyl 5-ferrocenyl-3,5-dimethyl-2-pyrazoline-1-dithiocarboxylate (1) or benzyl 5-ferrocenyl-3,5-dimethyl-2-pyrazoline-1-dithiocarboxylate (2). The single crystals of both products are obtained and their structures are identified by X-ray diffraction method with triclinic P-1 space groups. The cell parameters for compound 1 are as follows: a = 7.7029(8) Å, b = 10.1631(11) Å, c = 10.7305(12) Å, α = 101.3270(10)°, β = 90.6740(10)°, γ = 94.8390(10)°, and V = 820.40(15) ų. For compound 2, the crystallographic data are: a = 7.953(3) Å, b = 10.970(5) Å, c = 12.534(3) Å, α = 84.718(5)°, β = 81.651(3)°, γ = 76.274(4)Å, and V = 1049.1(7) ų.     

Synthesis, structure characterization and preliminary biological evaluation of novel 5-alkyl-2-ferrocenyl-6,7-dihydropyrazolo[1,5-a]pyrazin-4(5H)-one derivatives

A series of novel 5-alkyl-2-ferrocenyl-6,7-dihydropyrazolo[1,5-a]pyrazin-4(5H)-one derivatives were synthesized by the reaction of ethyl 1-(2-bromoethyl)-3-ferrocenyl-1H-pyrazole-5-carboxylate with non-aromatic primary amines in one-pot procedure and characterized by ¹H NMR, ¹³C NMR, IR, HRMS and X-ray diffraction analysis. The effects of all the compounds on A549 cell growth were investigated. The results showed that all compounds had almost inhibitory effects on the growth of A549 cells.     

Protophilic isotopic hydrogen exchange of 1-ferrocenyl-2-(nitrophenyl)ethylenes

cis-1-Ferrocenyl-2-(4-nitrophenyl)ethylene enters into the protium/deuterium exchange in basic medium at the expense of hydrogens of the phenyl ring, at ortho positions in respect of the nitro group. The homoaromatic analogue, 4-nitrostilbene, under the same conditions, undergoes isotopic exchange occurring exclusively at the vinylic CH fragment attached to the nitrophenyl group. The difference is eliminated as a result of the shift of the nitro group from position 4 into position 2 of the phenyl ring: cis-1-ferrocenyl-2-(2-nitrophenyl)ethylene enters into H⁺/D⁺ exchange in the same manner as 4-nitrostilbene. Correspondence to: Professor Z.V. Todres.     

3-Alkenyl-5-ferrocenyl-2-pyrazolines in reactions with azodicarboxylic acidN-phenylimide

Azodicarboxylic acidN-phenylimide reacts with 1-acetyl-3-(2-ferrocenylethenyl)-5-ferrocenyl-2-pyrazoline according to the [4+2]-cycloaddition mechanism to form a Diels—Alder adduct. Under analogous conditions, 1-acetyl-5-ferrocenyl-3-(1-cyclohexenyl)-substituted 2-pyrazolines containing allylic hydrogen atoms give monoene addition products. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 908–913, May, 2000.     

“Push-pull” 2-ferrocenyl-4-hydroxythiazoles: A novel method of the construction of the thiazole ring

The title compounds were obtained by cyclization of ferrocenyl thioimidates in the presence of sodium ethoxide. They were transformed into the corresponding 4-acetoxy-derivatives in reaction with acetic anhydride/pyridine. The structure of 4-acetoxy-5-(ethoxycarbonyl)-2-ferrocenylthiazole was determined by X-ray diffraction. The EFISH measurements revealed significant second-order nonlinear properties of 4-acetoxy-2-ferrocenyl-5-(4-nitrophenyl)ferrocenylthiazole (μβ = 250 × 10⁻⁴⁸ esu at 1907 nm).     

Polymerization studies on 1-ferrocenyl-1,3-butadiene

The polymerization behavior of 1-ferrocenyl-1,3-butadiene has been investigated by using both free-radical and anionic initiation techniques. Polymerization occurred readily under the promoting action of butyllithium; however, no polymerization occurred when azobisisobutyronitrile (AIBN) or benzoyl peroxide was employed as initiator. Copolymerizations were carried out with methyl methacrylate and styrene. The behavior of 1-ferrocenyl-1,3-butadiene in the copolymerizations was followed by dilatometric rate measurements, solution viscosity determinations, and elemental analysis. The major effect observed was a severe reduction in the intrinsic viscosities of the copolymers. An explanation for the observed behavior of 1-ferrocenyl-1,3-butadiene in these reactions is advanced.     

Unexpected reactions of ferrocene acetal derived from tartaric acid with alkyllithium: competition between proton abstraction and nucleophilic attack

We wished to prepare planar chiral compounds by the lithiation of acetal 2-ferrocenyl-(4S,5S)-bis(methoxymethyl)-1,3-dioxolane (1) with butyllithium followed by the reaction with an electrophile. However, the desired products were not observed and two unexpected products, 1-ferrocenyl-1-pentanol (4) of the nucleophilic attack product and 2-ferrocenyl-4,5-dimethylene-1,3-dioxolane (5) of the proton abstraction product, were isolated. Because the nucleophilic attack on acetal carbon is rarely reported so far and both products 4 and 5 may have some potential uses in organic synthesis, these unexpected reactions are investigated in detail. The mechanisms of these reactions are discussed.     

Crystal and molecular structure of 2-ferrocenyl-2-propanol

The crystal and molecular structure of 2-ferrocenyl-2-propanol is studied by means of physicochemical methods. The compound crystallizes in the form of three crystallographically independent molecules with slightly different conformations. Crystals are monoclinic, C₁₃H₁₆FeO: a = 6.2687(7) Å, b = 36.614(4) Å, c = 15.291(2) Å; β = 97.86(2)°; V = 3477.2(7) ų, Z = 12, d x = 1.396 g/cm³, P2₁/n space group. The molecule consists of the ferrocene fragment and the isopropyl carbinol substituent.     

Synthesis, characterization, spectroscopic and electrochemical properties of phthalocyanines substituted with four 3-ferrocenyl-7-oxycoumarin moieties

The synthesis, spectroscopic and electrochemical properties of the tetra-(3-ferrocenyl-7-oxycoumarin)-substituted zinc (II) and cobalt (II) phthalocyanines (3 and 4) are reported for the first time. The synthesis of novel 3-ferrocenyl-7-hydroxycoumarin (1) was performed according to Perkin reaction, and the ligand, 7-(3,4-dicyanophenoxy)-3-ferrocenylcoumarin (2), was synthesized by the reaction of 3-ferrocenyl-7-hydroxycoumarin with 4-nitrophthalonitrile in the presence of K₂CO₃ as the base in dry dimethylformamide. The preparation of the corresponding zinc (II) and cobalt (II) metallo phthalocyanines (3 and 4) substituted with 3-ferrocenyl-7-oxycoumarin moieties at β-positions of the phthalocyanine ring was achieved by the cyclotetramerization of the coumarin ligand (2) with relevant metal(II) acetates in dry 2-dimethylaminoethanol. The new compounds have been characterized by elemental analyses, FT-IR, ¹H NMR, Mass and electronic spectroscopy. The fluorescence property of the zinc metallo phthalocyanine (3) is strongly affected by the presence of ferrocenyl moiety. The ferrocenyl moieties were very efficient in quenching the excited state of 3, which show very poor fluorescent intensity. The electrochemical properties of the complexes were also investigated by cyclic and differential pulse voltammetry techniques in non-aqueous medium. It was found that the redox-active ferrocene substituents are reduced concurrently at one potential.     

The synthesis, structural characterization and in vitro anti-cancer activity of novel N-(3-ferrocenyl-2-naphthoyl) dipeptide ethyl esters and novel N-(6-ferrocenyl-2-naphthoyl) dipeptide ethyl esters

N-(3-ferrocenyl-2-naphthoyl) dipeptide esters (5-7) and N-(6-ferrocenyl-2-naphthoyl) dipeptide esters (8-10) were prepared by coupling either 3-ferrocenylnaphthalene-2-carboxylic acid 2 or 6-ferrocenylnaphthalene-2-carboxylic acid 4 to the dipeptide ethyl esters GlyAla(OEt) (5, 8), AlaGly(OEt) (6, 9), and AlaAla(OEt) (7, 10) using the standard N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), 1-hydroxybenzotriazole (HOBt) protocol. All the compounds were fully characterized using a combination of ¹H NMR, ¹³C NMR, DEPT-135 and ¹H-¹³C COSY (HMQC) spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and cyclic voltammetry (CV). In vitro, the cytotoxic effects of compounds 5-10 show improvements over the corresponding N-(ferrocenyl)benzoyl derivatives, with IC₅₀ values against the H1299 lung cancer cells ranging from 1.2 μM to 8.0 μM. N-(6-ferrocenyl-2-naphthoyl)-glycine-l-alanine ethyl ester 8 was found to be the most active derivative of the naphthoyl series so far, displaying an IC₅₀ value of 1.3 ± 0.1 μM. This value is slightly lower than that found for the clinically employed anti-cancer drug cisplatin (IC₅₀ = 1.5 ± 0.1 μM against H1299).     

Synthesis and biological activity research of novel ferrocenyl-containing thiazole imine derivatives

A series of novel N-substituted benzylidene-4-ferrocenyl-5-(1H-1,2,4-triazol-1-yl)-1,3-thiazol-2-amine derivatives were synthesized by condensation of substituted-benzaldehydes with 2-amino-4-ferrocenyl-5-(1H-1,2,4-triazol-1-yl)-1,3-thiazole and characterized by ¹H NMR, X-ray diffraction and elemental analysis. The results of bioassay showed that some title compounds exhibited some degree of plant growth regulatory and antifungal activities.     

The replacement of a phenol group by an aniline or acetanilide group enhances the cytotoxicity of 2-ferrocenyl-1,1-diphenyl-but-l-ene compounds against breast cancer cells

We have previously shown that conjugated ferrocenyl p-phenols show strong cytotoxic effects against both the hormone-dependent MCF-7 and hormone-independent MDA-MB-231 breast cancer cell lines, possibly via oxidative quinone methide formation. We now present a series of analogous amine and acetamide compounds: 2-ferrocenyl-1-(4-aminophenyl)-1-phenyl-but-1-ene (Z+E-2), 2-ferrocenyl-1-(4-N-acetylaminophenyl)-1-phenyl-but-1-ene (Z-3), and their corresponding organic molecules 1-(4-aminophenyl)-1,2-bis-phenyl-but-1-ene (Z+E-4) and 1-(4-N-acetamidophenyl)-1,2-bis-phenyl-but-1-ene (Z+E-5). All of the compounds have adequate relative binding affinity values for the estrogen receptor; between 2.8% and 5.7% for ERα, and between 0.18% and 15.5% for ERβ, as well as exothermic ligand binding in in silico ER docking experiments. Compounds 2 and 3 show dual estrogenic/cytotoxic activity on the MCF-7 cell line; they are proliferative at low concentrations (0.1 μM) and antiproliferative at high concentrations (10 μM). On the MDA-MB-231 cell line, the ferrocenyl complexes 2 and 3 are antiproliferative with IC₅₀ values of 0.8 μM for 2 and 0.65 μM for 3, while the purely organic molecules 4 and 5 show no effect. Electrochemical experiments suggest that both 2 and 3 can be transformed to oxidized quinoid-type species, analogous to what had previously been observed for the ferrocene phenols.     

Developing click reactions of a 3-ferrocenyl-2H-azaphosphirene complex

Atom efficient reactions of 3-ferrocenyl-2H-azaphosphirene complex 1 using a newly developed acid/base ring expansion protocol are presented. Consecutive reaction of 1 in the presence of dimethyl cyanamide with triflic acid and triethylamine yielded the selective formation of 2H-1,4,2-diazaphosphole complex 3. The same protocol using acetone, benzaldehyde and ferrocenyl aldehyde afforded 1,3,5-oxazaphosphol-3-ene complexes 4, 5a,b and 6a,b, the latter as mixtures of diastereomers, which could be separated. Apart from NMR, IR and UV/vis spectroscopic data, the single-crystal X-ray structures of complexes 3, 4 and 6a are discussed.     

Crystal structure of 6-ferrocenyl-3-phenyl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole

A new compound of 6-ferrocenyl-3-phenyl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole is synthesized and its single crystal structure is determined by X-ray diffraction method. The compound belongs to the monoclinic P2₁/c space group with cell parameters: a = 10.5523(12) Å, b = 13.8414(16) Å, c = 11.4303(13) Å, V = 1603.5(3) ų.     

1′-Carbopalladated-4-ferrocenyl-1,3-oxazolines as catalysts for Heck reactions: Further evidence in support of the Pd(0)/Pd(II) mechanism

1′-Carbopalladated complexes derived from 4-ferrocenyl-1,3-oxazolines are reported in this paper as efficient catalysts for the Heck coupling of iodo- and bromoarenes with alkenes. Experimental evidence points out strongly towards the involvement of a Pd(0)/Pd(II) catalytic cycle in the mechanism of the reaction. For the first time, the disassembly of the carbopalladated complex via coupling with the olefin in a non-catalytic Heck reaction has been demonstrated to be the origin of the release of Pd(0) from the palladacycle carrier.