Presence Of Cp2TiCl2 Research Articles

Catalytic cyclometallation in steroid chemistry V: Synthesis of hybrid molecules based on steroid oximes and (5Z,9Z)-tetradeca-5,9-dienedioic acid as potential anticancer agents

Synthetic analogues of natural 5Z,9Z-dienoic acids - hybrid molecules based on the oximes of cholesterol, pregnenolone, and androsterone with 1,14-tetradeca-5Z,9Z-dienedicarboxylic acid - were synthesized for the first time and studied for antitumor activity in vitro. The acid was prepared using catalytic cyclomagnesiation of O-containing 1,2-dienes with Grignard reagent in the presence of Cp2TiCl2 as the key step. Using flow cytometry, it was shown for the first time that the new molecules are efficient apoptosis inducers in the HeLa, Hek293, U937, Jurkat, and K562.

Catalytic cyclometallation in steroid chemistry VI: Targeted synthesis of hybrid molecules based on steroids and tetradeca-5Z,9Z-diene-1,14-dicarboxylic acid and study of their antitumor activity

Hybrid molecules based on a number of steroids (cholesterol, pregnenolone, androsterone) and 1,14-tetradeca-5Z,9Z-dienedicarboxylic acid linked via mono- and diethylene glycol spacers were synthesized for the first time and studied for antitumor activity in vitro. The acid was prepared using catalytic cyclomagnesiation of oxygenated 1,2-dienes with Grignard reagent in the presence of Cp2TiCl2 as the key synthetic step. Using flow cytometry, the new molecules were shown for the first time to be efficient apoptosis inducers in the HeLa, Hek293, U937, Jurkat, and K562 cell cultures and to have dose-dependent effect on the S and G2 phases of the cell cycle.

Mechanism of catalytic cycloboration of α-olefins with boron trichloride: the synthesis of hardly obtainable boriranes and the mechanistic DFT study of transmetalation of titanacyclopropane intermediates

A theoretically justified mechanism of transmetalation of 2-alkyl substituted titanacyclopropanes with BCl3 is proposed based on the DFT calculations of the thermodynamic and activation parameters of possible reaction pathways. Based on the data obtained, phenyl- and alkyldichloroboranes were proposed to be used as transmetalating agents along with BCl3 in the catalytic cycloboration in the presence of Cp2TiCl2 and Mg metal. It was shown that the barely accessible 1-phenyl-2-hexylborirane can be synthesized using PhBCl2.

Total Synthesis of Neuritogenic Alkynes: Lembehyne B and Key Intermediate of Lembehyne A

AbstractA new Ti‐catalyzed cross‐cyclomagnesiation of aliphatic and oxygenated 1,2‐dienes with EtMgBr in the presence of Cp2TiCl2 was used in the key stage for the development for the first time original methods for the preparation of racemic and natural neuritogenic alkynes lembehyne B and stereoselective syntheses of (4Z,8Z)‐pentacosa‐4,8‐dien‐1‐ol ‐ the key intermediate in the total synthesis of lembehyne A.

Cp2TiCl2-catalyzed cycloboration of α-olefins with PhBCl2 in the synthesis of 2-alkyl(aryl,benzyl)-1-phenylboriranes

A one-pot method for the synthesis of 2-alkyl(aryl, benzyl)-1-phenylboriranes has been developed via the reaction of α-olefins with PhBCl2 in the presence of Cp2TiCl2 as the catalyst. The method implies the formation of boriranes as the result of transmetalation of titanacyclopropane intermediates generated in the reaction of α-olefins with Cp2TiCl2. Individual 1-phenyl-2-substituted boriranes were isolated and their structures confirmed by NMR spectral methods.

Short Route to the Total Synthesis of Natural Muricadienin and Investigation of Its Cytotoxic Properties

An original synthesis of the acetogenin muricadienin, the bioprecursor of solamin, has been developed. The key step in the five-step 41% overall yield synthesis is the catalytic cross-cyclomagnesiation reaction of functionally substituted 1,2-dienes with EtMgBr in the presence of Cp2TiCl2 and magnesium metal. It has been demonstrated for the first time that muricadienin exhibits a moderate in vitro inhibitory activity against topoisomerases I and IIα, key cell cycle enzymes. Using flow cytometry, muricadienin was shown to have high cytotoxicity toward the HEK293 kidney cancer cells (IC50 0.39 μM).

Synthesis of tetrasubstituted furans by multicomponent reaction of alkynes with dichloro(ethyl)aluminum and carboxylic acid esters in the presence of Cp2TiCl2

A one-pot procedure has been developed for the synthesis of 3,4-dialkyl-2,5-dicycloalkyl(aryl, hetaryl)furans in 38–82% yield by reaction of symmetrical alkynes with cycloalkane(arene, hetarene)carboxylic acid esters and EtAlCl2 in the presence of Cp2TiCl2 as catalyst.

Aqueous emulsion homo- and copolymerization of 1,3-dienes and styrene in the presence of Cp2TiCl2

Bis-cyclopentadienyl titanium dichloride (Cp2TiCl2) is utilized as initiator for aqueous emulsion homopolymerization of 1,3-butadiene and isoprene and for copolymerization of the same diene monomers with styrene. The obtained homo- and copolymers are fully characterized by 13C nuclear magnetic resonance spectroscopy, thermal analysis and gel permeation chromatography.

Aqueous emulsion polymerization of styrene and substituted styrenes using titanocene compounds

Aqueous emulsion polymerization of styrene in the presence of half-titanocenes which CpTiCl3, (CpCH2CH2OCH3)TiCl3, and of the titanocene (Ph)2C[(Cp)(Flu)Ti]Cl2 is effected. The polymer features are compared with those of polystyrene obtained in the same reaction conditions, by using Cp2TiCl2 as initiator.Titanocene (Ph)2C[(Cp)(Flu)Ti]Cl2 does not show any activity in styrene polymerization. On the contrary, by using both half-titanocenes CpTiCl3 and (CpCH2CH2OCH3)TiCl3, stereoirregular polystyrene is produced. Aqueous emulsion polymerization of substituted styrenes (3-methyl-styrene, 4-methyl-styrene, 3-chloro-styrene, 4-chloro-styrene) is also performed in the presence of Cp2TiCl2. From all monomers, stereoirregular polymers are obtained. Monomer reactivity results dependent on the substituent on the aromatic ring. Aqueous emulsion styrene – 4-chloro-styrene copolymerizations are performed by using Cp2TiCl2, too. Copolymer composition totally reflects that of comonomers used in the feeding. According to a statistical distribution of comonomers, the product of the reactivity ratios is 1.1.

Synthesis and transformations of metallacycles 41. Cyclomagnesiation of O-containing 1,2-dienes with Grignard reagents in the presence of Cp2TiCl2

A Cp2TiCl2-catalyzed intermolecular homocyclomagnesiation of O-containing 1,2-dienes and cross-cyclomagnesiation of O-containing 1,2-dienes with aliphatic 1,2-dienes of cyclic and acyclic structure have been accomplished using Grignard reagents, which led to mono- and bicyclic organomagnesium compounds in 61–94% yields.

Electrocatalytic dehalogenation of α-bromoketones in the presence of Cp2TiCl2

Processes of direct and electrocatalytic (in the presence of electrochemically reduced Cp2TiCl2) reduction of three α-bromoketones containing the C(sp3)-Br or C(sp2)-Br bond, viz., 2-bromo-and 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-ones and α-bromo-acetophenone, were studied by cyclic voltammetry and preparative electrolysis. In all cases, the dissociative electron transfer proceeds via the concerted mechanism. Preparative electrolysis of these α-bromoketones in the presence of Cp2TiCl2 affords the reductive debromination products in 40–80% yield at low cathodic potentials (−0.85 V vs. Ag/AgCl/KCl). In the case of 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-one in the potentiostatic regime, only one bromine atom can be eliminated selectively.

Titanocene‐Catalyzed Regioselective Carbomagnesation of Alkenes and Dienes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthetic and Electrochemical Studies on 1,1‘-Dithia-Substituted Derivatives of Ferrocene and Structure of 1,3-Dithia[3]ferrocenophane [Fe(C5H4S)2CH2

The bimetallic complexes fc(μ2-S)2TiCp2 (1, fc = 1,1‘-ferrocenyl, Cp = cyclopentadienyl) and fc(μ2-S2)(μ2-S)TiCp2 (2) were synthesized by reaction of fc(SH)2 with Cp2TiCl2, and from fcS3 and Cp2Ti(CO)2, respectively. The novel tetrasulfane fcS4 was obtained from 2 and SCl2. 1,3-Dithia[3]ferrocenophane fcS2CH2 was obtained from fc(SH)2 and CH2Cl2 in the presence of Cp2TiCl2 and KOH. The molecular and crystal structure of fcS2CH2 was determined by X-ray crystallography; the molecular symmetry is Cs. Electrochemical studies on the recently prepared ferrocenophanes fcS2-1-SO, fcS2-1-SO2, and fcS2-2-SO show that, with respect to fcS3, the progressive oxidation of the trisulfane bridge makes more and more difficult the fc/fc+ oxidation, whereas insertion of a Cp2Ti fragment exerts the opposite effect.

Manganese-Promoted, Titanocene-Catalyzed Stereoselective Pinacol Coupling of Aldehydes

Aromatic and aliphatic aldehydes undergo pinacol coupling when treated with Mn/Me3SiCl in the presence of Cp2TiCl2 as catalyst. Good yields of bis-silyl pinacol ethers are obtained with varying degrees of diastereoselectivity. Enantioselective pinacolization has been achieved using an enantiomerically enriched catalyst

ChemInform Abstract: Hydroalumination of Alkynes with LiAlH4 in the Presence of Cp2TiCl2.

ChemInform Abstract: Hydroalumination of Alkynes with LiAlH4 in the Presence of Cp2TiCl2.

Studies on titanium organic compounds: VIII. Mechanism of vinyl polymerization in the presence of titanocene dichloride

The mechanism of catalytic polymerization of acrylonitrile in the presence of titanocene dichloride under light have been investigated by UV, NMR and ESR spectroscopy. Results of photochemical reaction monitored by UV and NMR showed that titanocene dichloride (Cp2TiCl2) in dimethyl sulfoxide system can be decomposed by light irradiation to give cyclopentadiene. ESR studies show that cyclopentadienyl free radical in photopolymerization system of Cp2TiCl2-acrylonitrile can be trapped by two kinds of spin trapping agents, phenyl-N-tert-butylnitrone and 2-methyl-2-nitrosopropane, respectively. Therefore, the radical mechanism of catalytic polymerization of acrylonitrile in the presence of Cp2TiCl2 under light is further confirmed.