Synthesis and transformations of metallacycles. 23. Cp2TiCl2-Catalyzed cyclometallation of fullerene C60 with EtAlCl2

1-Ethyl-2,3-fullerenoaluminacyclopropanes (EtAl)_n(²-C₆₀) were synthesized by the reaction of fullerene C₆₀ with an excess of EtAlCl₂ in the presence of Mg and using Cp₂TiCl₂ as the catalyst in a THF--toluene solution at 20 °C. Deuterolysis of fullerenoaluminacyclopropanes afforded a mixture of deuteriofullerenes C₆₀D_m, where m = 6--12.     

Synthesis and transformations of metallacycles. 27. Quantum-chemical study of the mechanism of styrene catalytic cyclometallation with triethylaluminum in the presence of Cp2ZrCl2

Cyclometallation of olefins with AlEt₃ in the presence of Cp₂ZrCl₂ affording five-membered monosubstituted cyclic organoaluminum compounds, was studied by the semiempirical quantum-chemical PM3 method. The proposed model of catalytic cycloalumination of styrene catalyzed by Cp₂ZrCl₂ is in a good accordance with experimental data obtained by dynamic NMR spectroscopy.     

Synthesis and transformations of metallacycles. 26. Cp2ZrCl2-Catalyzed cycloalumination of substituted allenes with Et3Al

Catalytic cycloalumination of 1-alkyl(phenyl)allenes with triethylaluminum (5 mol.% of Cp₂ZrCl₂ as the catalyst, 20 °C, 4 h, hexane) afforded methylene- and alkyl(benzyl)idene-substituted alumacyclopentanes.     

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.     

Synthesis and transformations of metallacycles

The Cp₂ZrCl₂-catalyzed reaction of arylolefins (styrene,o- andp-methylstyrenes,trans-stilbene, 1,4-diphenyl-1,3-butadiene) with AlEt₃ resulting in mono- and disubstituted alumacyclopentanes and substituted alumacyclopropanes was studied. The yield and ratio of cyclic organoaluminum compounds depend on the structure of the initial arylolefins and conditions of cycloalumination.     

Synthesis and transformations of metallacycles

A regioselective method for the synthesis of 1,1-dialkylcyclopropanes was developed. The method is based on the reaction of 2,3-dialkyl-1-ethylalumacyclopent-2-enes with an excess of dialkyl sulfates (Me₂SO₄ or Et₂SO₄). A plausible reaction mechanism was suggested. For Part 20, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1092–1095, June, 2000.     

Novel Mg-organic reagents in organic synthesis. Cp2TiCl2 catalyzed intermolecular cyclomagnesiation of cyclic and acyclic 1,2-dienes using Grignard reagents

High-yield (>80%) catalytic intermolecular cyclomagnesiation of cyclic and acyclic allenes with the aid of Grignard reagents has been realized in the presence of Cp₂TiCl₂. The synthesized unsaturated bi- and tricyclic organomagnesium compounds (OMC) have been successfully converted in situ into thiophenes, unsaturated ketones, cyclic and acyclic hydrocarbons with high regio- and stereoselectivity.     

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. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 977–983, May, 2007.     

Cp2TiCl2-Catalyzed reaction of grignard reagents with isocyanates,formation of carboxamide with rearranged carbonskeleton

Isocyanates react with isopropyl or sec-butylmagnesium bromide in the presence of a small amount of Cp₂TiCl₂ to afford amides with normal alkyl group. A possibl mechanism for this reaction is proposed.     

Cp2 TiCl 2-Catalyzed Reaction of Grignard Reagents with Diaryl Ketones,Formation of Pinacolic Coupling from Diaryl Ketones

Diaryl ketones react with Grignard reagents in the presence of a catalytic amount of Cp₂ TiC1 ₂ to give the corresponding pinacolic coupling products.     

Cp2TiCl2-Catalyzed reaction of grignard reagents with isocyanates,formation of reduction-coupling product of isocyanates

Phenylisocyanate and phenylthioisocyanate react with Grignard reagents in the presence of a small amount of Cp₂TiCl₂ at room temperature to afford reduction-coupling products, N-methyl-N, N′-diphenylurea and N-methyl-N, N′-diphenylthiourea.     

Synthesis of Cp*CH2PPh2 and its use as a ligand for the nickel-catalysed cross-coupling reaction of alkyl halides with aryl Grignard reagents

A new ligand, Cp*CH2PPh2 (Cp* = 1,2,3,4,5-pentamethyl-2,4-cyclopentadienyl), was prepared, and was used as a ligand for nickel-catalysed cross-coupling reaction of alkyl halides with aryl Grignard reagents, which nickel-phosphine complexes had never made possible.     

Synthesis and transformations of metallacycles 35. Joint cycloalumination of cyclic 1,2-dienes with disubstituted acetylenes and terminal allenes under the action of EtAlCl<Subscript>2</Subscript> catalyzed by Ti and Zr complexes

Catalytic intermolecular cycloalumination of cyclic 1,2-dienes with terminal allenes or disubstituted acetylenes mediated by EtAlCl₂ in the presence of complexes based on transition metals was accomplished. The yield of unsaturated bicyclic aluminacarbocycles was up to 85%.     

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.     

Synthesis and transformations of metallacycles 39. Zr-Catalyzed cyclomagnesiation of N-containing allenes

Catalytic cyclomagnesiation of N-containing 1,2-dienes with Et₂Mg in the presence of the Zr-based complexes affords 2-(aminoalkylidene)magnesacyclopentanes in 68–84% yields.     

Spirocyclisation of phytoalexin 1-methoxybrassinin in the presence of Grignard reagents

The anti-cancer properties of naturally occurring (2R, 3R)-(?)-1-methoxyspirobrassinol methyl ether (I) and their synthetic amino or piperidyl analogues II inspired us to study the synthesis of new target compounds III with a C—C bond in the 2-position of indole rather than a C—N or C—O bond (I or II respectively). The goal was achieved via electrophilic-nucleophilic 3,2-difunctionalisation of 1-methoxybrassinin (IV) in the presence of bromine and the Grignard reagent leading to the formation of cis- and trans-C—C analogues of I. Finally, the anti-cancer activities of the new compounds were measured and compared with I and II in order to show the importance of a heteroatom in the 2-substituted indole on the anti-cancer activity of spirobrassinols.     

Synthesis and transformations of metallacycles 38. The Cp2ZrCl2-catalyzed cyclometallation of ��,��-diynes upon the action of RMgR�� or R n AlCl3?n

The Cp₂ZrCl₂-catalyzed cyclometallation of ??,??-alkadiynes upon the action of RMgR?? or R _n AlCl_3?n was accomplished to yield unsaturated di- and tricyclic (magnesa)aluminacarbocycles in up to 85% yield.     

Synthesis and transformations of metallacycles. 24. Zr-Catalyzed cycloalumination of asymmetrical disubstituted acetylenes

Cp₂ZrCl₂-Catalyzed cycloalumination of asymmetrical alkyl-, phenyl-, and allyl-substituted acetylenes under the action of Et₃Al was studied. The reactions afforded regioisomeric 2,3-disubstituted aluminacyclopent-2-enes whose yields and ratio depend on the nature of the substituents in the starting acetylenes.