Cross-coupling of allylic sulfides and grignard reagents catalyzed by nickel-phosphine complex

Allylic sulfides smoothly couple with Grignard reagents in the presence of Ni(II)-phosphine complexes as catalysts to give the corresponding unsaturated compounds in good yields.     

Phase-transfer catalyzed alkylation of pyrazoles and 1,2,4-triazole with cis- and trans-1,4-dichloro-2-butenes

The phase-transfer catalyzed (PTC) alkylation of pyrazoles and 1,2,4-triazole with cis- and trans-1,4-dichloro-2-butenes (DCB) has been examined. The monoalkylation products of pyrazoles with cis-DCB are bicyclic salts formed by intramolecular cyclization of the intermediate cis-1-(4-chloro-2-butenyl)pyrazoles. The corresponding trans-compounds are incapable of cyclization, but on prolonged standing they undergo intermolecular polyquaternization. Both cis- and trans-DCB undergo phase-transfer catalyzed reaction with 1,2,4-triazole to give polymeric quaternary salts. Conditions have been worked out for the dehydrochlorination of 1-(4-chloro-2-butenyl)azoles to 1-(butadien-2-yl)azoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 497–503, April, 1989.     

Macrocycles with sulfide and amine binding sites as chiral ligands for nickel catalyzed cross coupling of a grignard reagent with vinyl bromide

Synthetic routes to macrocycles derived from (S)-phenyl alanine and (S)-cysteine have been developed. The catalyzed coupling of the Grignard reagent of 1-chloro-1-phenylethane and vinyl bromide in the presence of these ligands proceeds usually in good yields and in enantiomeric excesses (e.e.) of up to 46%.     

One-pot synthesis of homoallylic ketones from the addition of vinyl grignard reagent to carboxylic esters

Fifteen homoallylic ketones have been synthesized in 26-77% yields on treatment of aromatic, aliphatic, and alpha-amino methyl carboxylates with excess vinylmagnesium bromide and catalytic amounts of a copper salt in THF. Alpha-amino homoallylic ketones derived from N-protected alpha-amino esters possessing aliphatic and alcohol side chains were synthesized in > or =98% enantiomeric purity. [reaction: see text]     

Polymerization of ethylene catalyzed by titanocene(iii) -b-diketonate complex and MMAO

Ethylene polymerizations were performed with a catalytic system composed of titanocene(III)-β-diketonate complex such as [Cp2Ti(III)(1-benzoylacetonato)] or [Cp2Ti(III)(dibenzoylmethanato)] and MMAO. These catalysts are active for the polymerization of ethylene to give high-density polyethylene with high molecular weight. This revised version was published online in June 2006 with corrections to the Cover Date.     

Formation of complex organics from acetylene catalyzed by ionized benzene

We present direct evidence for low temperature associative charge transfer (ACT) reactions of acetylene onto the benzene cation that catalyze the conversion of acetylene molecules into polymerized cations and for high temperature addition/elimination reactions that lead to the generation of naphthalene-type ions. At low temperatures acetylene molecules bind noncovalently to the benzene cation, where partial charge transfer from the ion activates an acetylene molecule for addition polymerization with other associated acetylene molecules, thus amounting to catalytic cyclization/polymerization of the acetylene molecules. At high temperatures the barrier of the covalent addition of acetylene to the benzene cation to form a styrene-type ion is measured as 3.5 kcal/mol. The second acetylene addition followed by H elimination to form a naphthalene-type ion is calculated to be highly exothermic and without a barrier. These reactions can explain the formation of complex organics by gas phase ion-molecule reactions under a wide range of temperatures and pressures in astrochemical environments.     

Hexachloroethane: a highly efficient reagent for the synthesis of chlorosilanes from hydrosilanes

A new and efficient chlorination protocol is presented for the preparation of chlorosilanes from hydrosilanes. A variety of chlorinating agents in combination with palladium(II) chloride as the catalyst are examined. Among them, hexachloroethane is found to be the best choice, furnishing the desired product in good to quantitative yields under mild conditions. Various hydrosilanes are used as starting materials to explore the scope of this reaction.     

Cross-coupling reactions of aryl and vinyl chlorides catalyzed by a palladium complex derived from an air-stable H-phosphonate

A palladium complex derived from air-stable TADDOLP(O)H catalyzes efficiently Hiyama, Stille, Kumada and Suzuki cross-coupling reactions of aryl and vinyl chlorides.     

Synthesis of enol and vinyl esters catalyzed by an iridium complex

Enol and vinyl esters were successfully synthesized by the use of an iridium complex as a catalyst. The reaction of carboxylic acids with terminal alkynes in the presence of catalytic amounts of [Ir(cod)Cl]₂ and Na₂CO₃ gave the corresponding 1-alkenyl esters. The addition of carboxylic acids to alkynes principally took place in the Markovnikov fashion. In addition, by the use of an Ir complex combined with NaOAc various vinyl esters were prepared through the transvinylation between carboxylic acids and vinyl acetate.     

Synthesis of a lignan skeleton via nickel- and palladium-phosphine complex catalyzed grignard coupling reaction of halothiophenes

A lignan skeleton is prepared in good yield through desulfurization of 3,4-dibenzyl-thiophene or 2,5-diaryl-3,4-dimethylthiophenes which are obtained by the nickel- or palladium-phosphine complex catalyzed Grignard cross-coupling reaction of halothiophenes.     

双环戊二烯基二氯化钛催化下格氏试剂与偕二卤代烷的反应

本文作者进行了在双环戊二烯基二氯化钛催化下, 异丙基格氏试剂对偕二卤代烷的还原反应的研究, 这对扩大该催化还原体系的应用范围是有意义的。本文报道该反应的研究结果及可能的反应机理。     

Regio- and diastereoselective reductive coupling of vinylepoxides catalyzed by titanocene chloride

[reaction: see text] The Ti(III)-catalyzed reaction of a series of vinylepoxides leads, with regio- and E-diastereoselectivity control, to good-to-excellent yields of the corresponding homocoupling products. This homocoupling reaction, which involves a new C-C bond-forming method, takes place via a S(N)2' process between an allyltitanium species and the starting vinylepoxide. The process can be used for the rapid and efficient formation of highly valuable intermediates for organic synthesis, as well as new interesting homologues of natural products.     

Polymerization of vinyl chloride catalyzed by a titanium complex with an anionic oxygen tripod ligand

Poly(vinyl chloride) (PVC) was prepared using a titanium complex with an anionic oxygen tripod ligand [CpCo{P(O)(OEt)₂}₃]⁻ () as catalyst and methyl aluminoxane (MAO) as cocatalyst. The polymerization behavior was compared with that of pentamethyl cyclopentadienyl titanium trichloride (Me₅CpTiCl₃). It is observed that L_OEtTiCl₃ can polymerize vinyl chloride with activity comparable to that of Me₅CpTiCl₃. The PVC samples prepared with L_OEtTiCl₃/MAO exhibit bimodal molecular weight distribution and the fraction of high molecular weight peak decreases with polymerization temperature. The microstructure and thermal decomposition of the PVC obtained were studied. Five types of structural defect were detected by ¹H-NMR. Only saturated structural defects are found at low polymerization temperature, but at high polymerization temperature unsaturated structural defects, possibly resulting from dehydrochlorination of the saturated structural defects, appear as well. No head-to-head structural defect is observed. ¹³C-NMR shows that the PVC prepared by L_OEtTiCl₃ has an atactic stereostructure. Compared with the PVC from radical polymerization and anionic polymerization, the PVC samples prepared with L_OEtTiCl₃ show improved thermal stability.     

Cyclodehydration of cis-2-butene-1,4-diol with active methylene compounds catalyzed by a diphosphinidenecyclobutene-coordinated palladium complex

(π-Allyl)palladium triflate coordinated with 1,2-bis(4-methoxyphenyl)-3,4-bis(2,4,6-tri-t-butylphenylphosphinidene)cyclobutene (DPCB-OMe), [Pd(η³-C₃H₅)(DPCB-OMe)]OTf, efficiently catalyzes cyclodehydration of cis-2-butene-1,4-diol with active methylene compounds such as acetylacetone and ethyl acetoacetate in toluene in the presence of pyridine. The reactions can be performed in air, giving 2-vinyl-2,3-dihydrofurans in good to high yields.     

Chiral β-dimethylaminoalkylphosphines. Highly efficient ligands for a nickel complex catalyzed asymmetric grignard cross-coupling reaction

Chiral β-dimethylaminoalkylphosphines were prepared starting with amino acids, (S)-alanine, (S)-phenylalanine, (R)-phenylglycine, (S)-valine, and (R)-tert-leucine. The chiral phosphines were found to be highly efficient ligands for a nickel catalyzed asymmetric Grignard cross-coupling reaction (38～94% optical yield).     

1,4-Diazepinone and pyrrolodiazepinone syntheses via homoallylic ketones from cascade addition of vinyl Grignard reagent to alpha-aminoacyl-beta-amino esters

[reaction: see text] 1,4-Diazepinones 5 and pyrrolodiazepinones 8 and 9 were synthesized from common homoallylic ketone precursors 4 prepared by copper-catalyzed cascade addition of a vinyl Grignard reagent to alpha-aminoacyl beta-amino esters 3. Nitrogen deprotection and intramolecular reductive amination yielded 1,4-diazepinones 5. Olefin oxidation, Boc removal, and intramolecular Paal-Knorr condensation gave pyrrolodiazepinones 8 and 9. X-ray structures of diazepinones 5c and 5d depicted dihedral angles about the alpha-amino acid moiety similar to those of the central residue in an ideal reverse gamma-turn.     

Thermodynamics of vinyl ethers—XI: The effect of the alkoxy group on the relative stabilities of 2-alkoxy-3-methyl-1-butenes and corresponding 2-butenes

The effect of the alkoxy group (RO-; R=Me, Et, MeOCH₂CH₂, ClCH₂CH₂, i-Pr, s-Bu, (Et)₂CH, C₆H₅) on the relative stabilities of 2-alkoxy-3-methyl-1-butenes and corresponding 2-butenes has been studied by chemical equilibration in cyclohexane solution at various temperatures. The relative stability of the latter isomer is favored by (a) increasing size, (b) increasing electron-attracting character, and (c) increasing conjugative power of the R group. The last-mentioned point is especially important; in the case R = phenyl, the value of ΔH° (g, 298·15 K) of the isomerization of the former to the latter is 12–13 kJ mol^?1 more negative than in cases where conjugation between the ether oxygen and the R group is not possible.