Presence Of TiCl4 Research Articles

ChemInform Abstract: Chelate-Controlled Mukaiyama Reactions with Chiral β-Formyl Esters.

Abstract Additions of silyl enol ethers, 3, 6 , and 8 to chiral β-formyl esters 1 in the presence of TiCl 4 provide trans -γ-lactones 4, 7 , and 9 in high yield and with good to excellent diastereofacial selectivity. This high trans -preference is due to effective chelate-control involving seven-membered ring 1 -TiCl 4 complexes.

ChemInform Abstract: A New Type of Complex Reagent: R4Pb/TiCl4.

Abstract Tetraalkllleads (R 4 Pb) reacted quite smoothly with aldehydes R′CHO in the presence of TiCl 4 to produce the corresponding alcohols (RCHOHR′) in high to good yields. The reagent system, R 4 Pb/TiCl 4 , exhibited high chemoselectivity; only aldehydes underwent the alkylation in the presence of ketones. Further, the new reagent exhibited high 1,2- and 1,3-asymmetric induction. The transfer order of alkyl groups in the reaction of aldehydes with mixed tetraalkylleads/TiCl 4 was determined; Me>Et.i-Pr⪢n-Bu.

ChemInform Abstract: Evidence for Synclinal Transition State in the Reactions of Aromatic Aldehydes with α-(Alkoxy)allylstannanes.

Abstract Unlike aliphatic aldehydes, aromatic aldehydes produce greater than 95% of syn-(Z) enol ether when treated with α-(alkoxy)allylstannanes in the presence of BF3·Et2O. However, in the presence of TiCl4, the reaction of p-chloro-o-methoxybenzaldehyde with α-(alkoxy)crotylstannane produced predominantly the syn-(E) isomer.

ChemInform Abstract: Very High Diastereofacial Stereoselectivity in the α-Methoxy Organolead-Aldehyde Condensation. Stereocontrol of Three Contiguous Chiral Centres.

The reaction of the α-methoxylead derivative 1a with 2-phenylpropanal in the presence of TiCl4 gave the 1,2-syn-2,3-syn product 2 with very high diastereoselectivity: 1,2-syn/1,2-anti= 95/5 and 2,3-syn/2,3-anti= 100/0.

ChemInform Abstract: Stereoselective Synthesis of trans-2,5-Disubstituted Tetrahydrofurans via the Lewis Acid Mediated Reduction of Cyclic Hemiketals with Triphenylsilane.

An efficient method for the synthesis of trans-2,5-disubstituted tetrahydrofuran derivatives has been developed. Dithioacetal-functionalized cyclic hemiketals are reduced by triphenylsilane (Ph3SiH) in the presence of TiCl4 to afford the corresponding trans-2,5-disubstituted tetrahydrofuran derivatives in good yield and high stereoselectivity. Asymmetrical synthesis of (2S,5S) disubstituted tetrahydrofuran was also achieved by using this reduction method.

ChemInform Abstract: Synthesis and Basicity of 4-Amino-2-phenylquinazolines

A new group of 6- and 7-substituted compounds of 4-amino-2-phenylquinazoline were synthesized by reaction of N-arylbenzimidoyl chlorides with cyanamide in the presence of TiCl4. The products were identified by spectroscopic methods, their dissociation constants were determined and are discussed.

On reactions of spirostane sapogenins with benzeneseleninic anhydride

Direct dehydrogenation of spirostane sapogenins with benzeneseleninic anhydride/iodoxybenzene afforded the Δ 22 derivatives in low yields. The reactions catalyzed by BF 3/Et 2O produced the 23-oxo-sapogenins in addition to their 22-oxo-23-spiro-isomers. The reactions of sapogenins with benzeneseleninic anhydride carried out in the presence of TiCl 4 afforded products chlorinated at C23.

2-Fluoro-3-phenyl-allyltrimethylsilane: A new fluorinated reagent for Hosomi–Sakurai reaction

2-Fluoro-3-phenyl-allyltrimethylsilane, prepared from β-fluorinated allylic acetate via a π-allylpalladium intermediate, reacted with various aldehydes and acetals in the presence of TiCl 4 to afford the corresponding homoallyl alcohols and homoallyl ethers, respectively, in good to moderate yields.

The Chemistry of 3-Aminophospholes

A 3-morpholinophosphole has been prepared from the appropriate 3-keto-4-phospholene oxide by reaction with morpholine in the presence of TiCl4 as a catalyst, followed by reduction of the phosphoryl...

One-stage synthesis of poly[( p-phenylimino)-acenaphthene], a new macromolecular material with interesting electric properties

A new macromolecular material, a derivative of 1,2-bis-( p-aminophenylimino)-acenaphthene, was prepared. The monomer above, belonging to the group of small-molecule semiconductors, presents, as we referred in a previous work (Mhaidat [1]), remarkable photoconductive properties. The polymerization, a polycondensation reaction, was achieved in one-stage, using as starting materials acenaphthenequinone and p-phenylenediamine, in the presence of TiCl 4 and Dabco as catalysts, into o-dichlorobenzene acting as a solvent. The product obtained was fully characterized with mass spectroscopy, 1H NMR and FTIR techniques. Mass spectrum permitted the calculation of the polymer's molecular weight, being equal to 1633.85, whereas measurements of electric properties confirmed its semiconductive character.

Trans-2,5-Disubstituted Tetrahydrofurans via Addition of Carbon Nucleophiles to the Strained Bicyclic Acetal 2,7-Dioxabicyclo[2.2.1]heptane

Addition of allyltributylstannane to 2,7-dioxabicyclo[2.2.1]heptane in the presence of TiCl(4) produces 5-allyl-2-(hydroxymethyl)tetrahydrofuran with a trans/cis ratio of 93:7. The trans-selectivity is also observed in additions of various other carbon nucleophiles.

Asymmetric Diels–Alder cycloaddition of a di- P-stereogenic dienophile with cyclopentadiene

The Diels–Alder cycloaddition of the di- P-stereogenic dienophile ( S P, S P)- 1 leads to novel di- P-stereogenic norbornene derivatives and proceeds with moderate diastereoselectivity in the absence of a catalyst. In the presence of TiCl 4, however, the diastereoselectivity was raised to 9:1. The major diastereoisomer has been characterized crystallographically. The separation of the diastereomeric cycloadducts was possible by fractional crystallization in the presence of (−)- O, O-dibenzoyltartaric acid monohydrate.

エノラート化学の開発と天然生理活性物質の全合成

Methodologies with chiral enolates including the stereoselective construction of the quaternary carbon, rearrangement of the vinylketene N,O-acetals, the remote stereoinduction with vinylketene silyl N,O-acetals, and the construction of 1,2-diols having the tertiary alcohol have been developed to apply to the natural product synthesis.Each isomer at the quaternary carbon has been synthesized from one enantiomer of α,β-unsaturated imide by choosing whether alkylation of the dienolate anion or rearrangement of the vinylketene N,O-acetal with MeAlCl2. The vinylketene silyl N,O-acetals possessing the chiral auxiliary reacted with aldehydes in the presence of TiCl4 to realize the stereocontrol at the γ and δ positions. Aldol reactions with lactate having the chiral auxiliary provided the 1,2-diols possessing the tertiary alcohol. The major stereoisomer depended on the chiral auxiliary and the protective group on the hydroxy group of lactate.These methodologies realized the short-step syntheses of natural products.

Trans-Stereoselectivity in the Reaction between Homophthalic Anhydride and Imines

The reaction between homophthalic anhydride and imines in the presence of TiCl4 and diisopropyl ethyl amine is trans-selective. Under these conditions, the reaction using homochiral imines can be highly diastereoselective, thus allowing the synthesis of enantiopure 1,2,3,4-tetrahydro-1-oxoquinoline-4-carboxylic acids.

One-Pot Synthesis of Functionalized Piperid-4-ones: A Four-Component Condensation

The one-pot synthesis of highly substituted piperid-4-ones has been achieved. Diketene is added to a tosyl imine in the presence of TiCl(4) and MeOH, followed by 1 equiv of aldehyde to generate 2,6-disubstituted nonsymmetrical piperid-4-ones as a mixture of cis-/trans-diastereomers in good yields. This mixture of diastereomers can be converted to a single 2,6- cis-diastereomer by epimerization with K(2)CO(3).

The Tetracyanoquinodimethane Motif in Overcrowded Bistricyclic Aromatic Enes: Avoiding Thermochromism

AbstractThe overcrowded bistricyclic aromatic enes (BAEs) [10‐[10‐(dicyanomethylene)‐9(10H)‐anthracenylidene]‐9(10H)‐anthracenylidene]propanedinitrile (7) and [10‐[10‐oxo‐9(10H)‐anthracenylidene]‐9(10H)‐anthracenylidene)]propanedinitrile(8) were synthesized by a condensation of bianthrone (2) with malononitrile in the presence of TiCl4 and pyridine. The crystal and molecular structure of 7 were determined. It crystallizes in two polymorphic forms, belonging to the space groups P21/c and P21/n. DFT calculations of 7 and 8 show that the overcrowding due to introducing dicyanomethylene substituents to 10 and 10′ positions is more pronounced in the twisted conformations, decreasing their stabilities. The enthalpy differences between the anti‐folded and the lowest lying twisted conformations in BAEs 7 and 8 are 61.3 and 42.3 kJ/mol, respectively. In accordance with theory, BAEs 7 and 8 do not exhibit thermochromic behavior. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Ti-catalyzed reactions of 4,4′-bis(trimethylsilyl)bicyclohexyl-2,2′-diene with various electrophiles

Reductive disilylation (Li + Me 3SiCl − THF) of 1,3-cyclohexadiene led to 4,4′-bis(trimethylsilyl)bicyclohexyl-2,2′-diene ( 1). In the presence of TiCl 4 in dichloromethane, 1 reacted with some acyl chlorides, anhydrides, and aldehydes to give tricyclo[7.4.0.0 3,8]trideca-4,12-diene-2-yl derivatives.

Thermal treatment effects on the Ru/CeO 2 catalysts performance for partial hydrogenation of benzene

The aim of this work is to study the effect of the preparation conditions of Ru/CeO 2 catalyst (calcination temperature and/or reduction) over the performance in the partial hydrogenation of benzene reaction in the presence of TiCl 3. The catalysts were prepared through chlorinated precursors by incipient wetness impregnation method. The reaction occurred in three-phase reactional medium in presence of water at 373 K and 5.0 MPa. Temperature programmed reduction (TPR) profiles of calcinated catalysts indicate the presence of oxidated ruthenium. X-ray photoelectron spectroscopy (XPS) analysis confirms this supposition, showing that the ruthenium appears in the form of RuO 2 for the sample calcinated at 673 K, while for the reduced solid at 773 K, the Ru appears in the metallic state. However, the calcination step followed or not by reduction, strongly hinders the catalytic performance. In its turn, the direct reduction leads to a more active Ru/CeO 2 catalysts, as well as higher cyclohexene yields throughout all the reaction.

Synthetic Studies toward C3‐C9 Segment of Soraphen A1α

The ring‐closure metathesis of the diene (2S,3R,4S)‐1‐(tert‐butyldiphenylsilyloxy)‐2,4‐dimethylhex‐5‐en‐3‐yl acrylate produced the dihydropyrone with the correct stereochemistry for Soraphen A1α synthesis. The C2,C3 stereocenters were introduced by the addition of the (Z)‐crotyl‐n‐butylstannane to the β‐alkoxyaldehyde(S)‐3‐(benzyloxy)‐2‐methylpropanal in presence of TiCl4 as a chelating catalyst to give the desired anti,syn homoallyic alcohol (2S,3R,4S)‐1‐(tert‐butyldiphenylsilyloxy)‐2,4‐dimethylhex‐5‐en‐3‐ol.

The Baylis-Hillman reaction of substituted aminomethylbenzotriazoles

Aminomethylbenzotriazoles react as effective Baylis-Hillman electrophiles with ethyl acrylate in the presence of TiCl4 at 20 oC to afford the corresponding benzotriazolated adducts in 66-80% yield. These adducts are (i) readily transformed to the Baylis-Hillman olefins by sodium hydride and (ii) smoothly undergo substitution of Bt with thiols.