Cp2TiCl2-catalyzed grignard reactions. 2. Reactions with ketones and aldehydes

The reaction of Grignard reagents with ketones or aldehydes in the presence of a catalytic amount of Cp₂TiCl₂ leads to the corresponding reduction products in high yields. Cp₂TiH intermediate was proposed to account for this observation.     

Cp2TiCl2-catalyzed hydromagnation of disubstituted acetylenes as a stereo-specific route to Z-alkenes

Conclusions The hydromagnation reaction of disubstituted acetylenes has been systematically studied in the presence of catalytic quantities of Cp_{cc 2}TiCl₂. It was found that the conditions used to form the catalytic complex exerted the decisive effect on the course of the reaction, and that the most active hydromagnation reagents were n-Pr₂Mg and i-Bu₂Mg.The hydrotitanation of disubstituted acetylenes using Cp₂TiH was also demonstrated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2156–2159, September, 1988.     

Cp2TiCl2-catalyzed synthesis of tetraalkyl-substituted pyrazines by the reaction of nitriles with EtAlCl2 and Mg

Tetraalkyl-substituted pyrazines were obtained by the multicomponent reaction of aliphatic linear nitriles with EtAlCl₂ in the presence of Mg and Cp₂TiCl₂ catalyst in 60–91% yields. The same processing of isobutyronitrile gave 2,4,5-triisopropyl-1H-imidazole in 56% yield.     

Lithium nitride reduction of Cp2TiCl2 and CpTiCl3: The synthesis of (Cp2TiCl2), Cp2TiCl2)n,Cp2Ti(CO)2 and chlorotetratitanium and nitridohexatitanium complexes

Stoichiometric reactions of Cp₂TiCl₂ or CpTiCl₃ with Li₃N in various molar ratios result in reduction to (Cp₂TiCl)₂, (CpTiCl₂)_n and (CpTiCl)₄ and provide useful synthetic routes. Further reduction produces hexanuclear nitrido titanium clusters, Cp₈Ti₆N and Cp₈Ti₆N₃, characterised from mass spectral evidence. The nitrido clusters react with HCl to form (Cp₂TiCl)₂ and Cp₂TiCl₂. (Cp₂TiCl₂ is also obtained by reaction with Me₃SiCl. Cp₂Ti(CO)₂ is formed by the reaction between Cp₂TiCl₂ and Li₃ N in THF in the presence of CO.     

Cp2TiCl2/BuiMgBr/THF体系还原二芳基二硒醚

有机硒化合物具有生物活性[14],将硒基团引入到有机分子的一般方法是使亲核性的硒金属盐与亲电试剂反应 .二芳基二硒醚是制备有机硒化合物的重要中间体 .当它被还原时转化为硒负离子 ,被卤素等氧化时转化为亲电的硒试剂 .还原二硒醚通常使用ＮａＢＨ4[5 ],最近报道一些新的方法 ,如使用水合肼 /甲醇钠体系[6 ],Ｓｍ/ＨｇＣｌ2 体系[7].本文报道Ｃｐ2 ＴｉＣｌ2 /ＢｕｉＭｇＢｒ/ＴＨＦ体系还原二芳基二硒醚 .1　结果与讨论Ｃｐ2 ＴｉＣｌ2 与ＢｕｉＭｇＢｒ反应产生的钛氢化物是一种强的还原剂[8].在室温下 ,钛氢化物很容易与二硒醚反应生成…     

Reductive Coupling of Aldimines Mediated with Samarium Catalyzed by Cp2TiCl2

Reductive coupling of aldimines into vicinal diamines mediated with samarium catalyzed by Cp₂TiCl₂ proceeds in refluxing THF with good yields.     

Titanium-catalyzed hydrosilylation of olefins: A comparison study on Cp2TiCl2/Sm and Cp2TiCl2/LiAlH4 catalyst system

Hydrosilylation of olefins catalyzed by Cp₂TiCl₂/Sm (Cp?=?cyclopentadienyl) under solvent free conditions have been investigated. By using Cp₂TiCl₂/Sm as catalyst system, β-adducts and hydrogenation products were detected. Hydrosilylation of olefins catalyzed by Cp₂TiCl₂/LiAlH₄ under room temperature has also been studied. The influence of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) on Cp₂TiCl₂/Sm and Cp₂TiCl₂/LiAlH₄, respectively, indicated that hydrosilylation of olefins catalyzed with Cp₂TiCl₂/Sm went through a free radical reaction pathway while a coordination mechanism was applied for Cp₂TiCl₂/LiAlH₄ catalyst system.     

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。     

Cp2TiCl2-catalyzed regio- and chemoselective one-step synthesis of gamma-substituted allylsilanes from terminal alkenes using dianion-type zincate (SiSiNOL-Zn-ate)

A regio-/chemoselective silylation reaction of various functionalized terminal alkenes in the presence of titanocene dichloride, based on a newly designed dianion-type zincate, was developed. The present silylation of terminal alkenes is a powerful tool for the one-pot generation of regiocontrolled functionalized allysilanes, which are available for various transformation reactions, such as hydroxyalkylation, epoxidation, and hydroboration.     

Cp2TiCl2/i-BuMgBr还原断裂Se—Csp键反应研究

Cp₂TiCl₂/i-BuMgBr体系形成的钛氢化试剂与炔硒醚反应生成端炔与深蓝色钛硒化物, 后者在空气中被氧化为二醚, 与酰氯反应, 高产率地形成对应的硒代酯.     

二茂二氯化钛存在下炔烃的还原反应

研究了双取代乙炔在二茂二氯化钛存在下被异丁基溴化镁格氏试剂还原生成烯烃的过程. 结果表明, 二苯乙炔还原后几乎得到专一的Z-二苯乙烯, 但多数炔烃还原后主要产物为E式烯烃, Z,E异构体的比例与底物炔烃的性质及位阻有关. 本文还报导了以双取代乙炔为底物, 径钛氢化反应合成了9组烯烃异构体混合物, 并对其结构进行了分析鉴定.     

Koordinationseigenschaften der isolobalen Phosphaniminatound Cyclopentadienyl‐Liganden in TiCl3(NPH3), TiCl3Cp,ReO3(NPH3) und ReO3Cp

Coordination Behaviour of the Isolobal Phosphoraneiminato and Cyclopentadienyl Ligands in TiCl₃(NPH₃), TiCl₃Cp, ReO₃(NPH₃), and ReO₃Cp The phosphoraneiminato and cyclopentadienyl complexes TiCl₃(NPH₃) ( 1 ), ReO₃(NPH₃) ( 2 ), TiCl₃Cp ( 3 ), and ReO₃Cp ( 4 ) have been investigated quantum chemically at the BP86/TZ(2)P level of nonlocal density functional theory (DFT). The metal–ligand bonds turn out to dissociate homolytically with the computed values for the corresponding bond dissociation energies amounting to 79.6 ( 1 ), 103.4 ( 2 ), 58.1 ( 3 ) and 45.0 ( 4 ) kcal/mol. Whereas the M–N–P unit in the titanium complex 1 is linear, we find a bent structure for the corresponding rhenium complex 2 (∠ Re–N–P = 136.4°). It turns out that the potential energy surface of the phosphoraneiminato complexes is extremely shallow with respect to the M–N–P angle; a variation over 50° is associated with an energy change of less than 2 kcal/mol. Furthermore, we have carried out a detailed analysis of the bonding in our model complexes to elucidate the difference in metal–ligand bond strengths between the isolobal phosphoraneiminato and cyclopentadienyl ligands.     

Silanolato-Komplexe von Titan und Zirconium. Die Kristallstrukturen von Cp2TiCl(OSiPh3) und Cp2ZrCl(OSiPh3)

Silanolato Complexes of Titanium and Zirconium. The Crystal Structures of Cp₂TiCl(OSiPh₃) and Cp₂ZrCl(OSiPh₃) The title compounds have been prepared by the reaction of Cp₂MCl₂ (M = Ti, Zr) with triphenylsilanole in diethylether in the presence of piperidine. They form only sparingly moisture sensitive orange (Ti) or colourless (Zr) crystal needles, which were characterized by X-ray crystallography. Cp₂TiCl(OSiPh₃): Space group P2₁/n, Z = 4, structure solution with 3961 observed unique reflections, R = 0.057. Lattice dimensions at 20°C: a = 1029.6, b = 1719.3, c = 1388.9 pm, β = 100.69°. The compound forms monomeric molecules with bond lengths TiO of 184.2 pm, SiO of 161.5 pm, and a TiOSi bonding angle of 164.5°. Cp₂ZrCl(OSiPh₃): Space group P3 , Z = 18, structure solution with 2799 observed unique reflections, R = 0.047. Lattice dimensions at ?20°C: a = b = 3518, c = 1058.3 pm. The structure consists of three symmetry-independent monomeric molecules, which differ only slightly. The bond lengths are (in average): ZrO 196.4 pm, SiO 162.1 pm, the ZrOSi bond angle is 173.7°.     

The Cp2ZrCl2-catalyzed cycloalumination of functionally substituted olefins with triethylaluminum

Reactions of functionally substituted olefins (allylamines, sulfides and ethers, homoallylic alcohols and amines, as well as vinyl ethers) with Et₃Al in the presence of Cp₂ZrCl₂ as a catalyst were studied. Cycloalumination of allylamines occurs with high regioselectivity to furnish after subsequent deuterolysis 4-deutero-2-(deuteromethyl)butyl-substituted amines. Cycloalumination of alkyl allyl sulfide is accompanied by a side process of the C-S bond cleavage. In the case of allyl and vinyl ethers, no cycloalumination products are formed under the reaction conditions. However, the reactions with homoallylic alcohol and amine after deuterolysis gave the corresponding dideutero-containing compounds in good yields.     

A Facile Reduction Procedure for Nitroarenes with Cp2TiCl2/Sm System

Nitroarenes can be reduced to the corresponding primary amines in good yields with Cp₂TiCl₂/Sm system under mild and neutral conditions.     

双环戊二烯基二氯钛催化下异丙基溴化镁对亚胺的还原反应

研究了在催化量的二茂钛氯化物存在下亚胺与异丙基溴化镁格氏试剂的反应.九个带有不同取代基的亚胺均以满意的得率还原成相应的胺.讨论了亚胺反应的机理.提出了在反应中有[CP2TiH]活性中间体存在.     

Cp2TiCl2-catalyzed grignard reactions. 3. Reactions with esters: Efficient methodology for the synthesis of secondary alcohols and for the reduction of esters to primary alcohols

Cp₂TiCl₂-catalyzed Grignard reactions with esters provide general methodology for preparation of secondary alcohols or for reduction of esters to the corresponding primary alcohols.