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

近年来,双环戊二烯基二氯化钛在有机合成中的应用得到迅速发展,从而开发了多种新型反应。其中双环成二烯基二氯化钛催化下,Grignard试剂的还原反应是研究得极为广泛的一类新反应。Cp_2Ticl_2/RMgX体系可以还     

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.     

Direct Coupling Reaction of Diaryl Methanol with Ketones or Aldehydes Catalyzed by AlCl3

A novel coupling reaction of diaryl methanols with ketones or aldehydes has been developed under the catalysis of AlCl₃. Various ketones and aldehydes could couple with 9H-xanthen-9-ol smoothly, affording coupling products in 48% –88% yields. A plausible mechanism using AlCl₃ to activate both diaryl methanol and ketone or aldehyde is proposed.     

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.     

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.     

铜催化下格氏试剂与酰卤的选择性偶合: 直链酮化合物的合成

在一般情况下,格氏试剂与酰卤偶合反应难以控制在酮阶段,往往得到叔醇。在较低温度下有机铜试剂与酰卤偶合可高产率地得到酮,所以用固体铜盐CuX(X=Cl、Br、I)作为格氏试剂与酰卤偶合的催化剂,可以提高反应的选择性,从而提高酮的产率。但固体铜盐的催化反应仅适合于空间位阻较大的脂肪酮和某些芳香酮的制备,对于直链脂肪酮的制备则产率很低。我们采用可溶性铜络合物Li_2Cucl_4(四氯合铜酸锂)等作催化剂,在均相溶液中反应,有效地提高了催化效果及反应的选择性,从而使格氏试剂与酰卤的偶合反应成功地用于直链脂肪酮的制备,产率良好。     

Cp2TiCl2催化下Grignard试剂与芳醛反应的研究

Meunier 等曾研究了 Cp_2TiCl_2催化下,格氏试剂对卤代烷和羰基化合物的还原反应,并报道了与芳环或碳-碳双键或碳-碳三键共轭的羰基化合物不被格氏试剂还原。我们却发现,在较低温度下,这些芳醛或与碳-碳重键共轭的羰基化合物也会被还原,特别是在芳环上有吸电子取代基时,还原产物的产率很高。     

CeCl3/Sm Promoted Pinacolic Coupling of Aromatic Aldehydes and Ketones

The pinacolic coupling of aromatic aldehydes and ketone was performed with cerium trichloride and samarium in THF at room temperature to afford the corresponding 1,2‐diols in good yields.     

Synthesis of Cyclohexyl and Isopropyl Ketones from Benzimidazole Methiodide Salt and Grignard Reagents

The reaction of 2-alkyl-l, 3-dimethylbenzimidazolinm salts with Grignard reagents gave addition products which were hy-drelyzed to give ketones. A new method for the preparation of cyclohexyl ketones and isopropyl ketones is provided.     

Fe‐Catalyzed Cross‐Coupling Reaction of Vinylic Ethers with Aryl Grignard Reagents

Iron‐catalyzed cross‐coupling reaction of vinylic ethers with aryl Grignard reagents is described. The reaction proceeded at room temperature with catalytic amounts of an iron salt without the aid of costly ligands and additives. In this catalytic system, vinylic C?O bonds were preferentially cleaved over aromatic C?O bonds of aryl ethers or aryl sulfonates.     

Continuous Flow Synthesis of Ketones from Carbon Dioxide and Organolithium or Grignard Reagents

We describe an efficient continuous flow synthesis of ketones from CO₂ and organolithium or Grignard reagents that exhibits significant advantages over conventional batch conditions in suppressing undesired symmetric ketone and tertiary alcohol byproducts. We observed an unprecedented solvent‐dependence of the organolithium reactivity, the key factor in governing selectivity during the flow process. A facile, telescoped three‐step–one‐flow process for the preparation of ketones in a modular fashion through the in‐line generation of organometallic reagents is also established.     

Sm(Hg) Promoted Pinacolic Coupling of Aromatic Aldehydes and Ketones

The pinacolic coupling of aromatic aldehydes and ketones was performed with samarium/mercury amalgam in THF at room temperature to afford the corresponding 1,2-diols in good yields.     

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.     

Zirconocene‐Mediated Carbonylative Coupling of Grignard Reagents

Organozirconocenes are versatile synthetic intermediates that can undergo carbonylation to yield acyl anion equivalents. Zirconocene hydrochloride ([Cp₂ZrHCl]) is often the reagent of choice for accessing these intermediates but generates organozirconocenes only from alkenes and alkynes. This requirement eliminates a broad range of substrates. For example, organozirconocenes in which the zirconium center is bonded to an aromatic ring, a benzylic group, or an alkyl group that possesses a tertiary or quaternary carbon atom α to the carbon–zirconium bond can not be formed in this way. To provide more generalized access to acyl zirconium reagents, we explored the transmetalation of Grignard reagents with zirconocene dichloride under a CO atmosphere. This protocol generates acyl zirconium(IV) complexes that are inaccessible with the Schwartz reagent, including those derived from secondary and tertiary alkyl and aryl Grignard reagents.     

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.     

Effect of Light on the Formation of Grignard Reagents

The effect of reflected sunlight on the formation of Grignard reagents has been reported¹. In the present work irradiation of mixtures of magnesium turnings and organic halides in dry diethyl ether by the method of Evans et al.² gave elevated yields of Grignard reagents as compared to those achieved in control experiments carried out in the absence of light. Four organic halides: 2-bromofluorene, 2-bromothiophene, chlorobenzene and chlorodiphenylmethane were selected for study in the light of their reputed poor performance in the Grignard reaction³. A quantitative estimate of the amount of Grignard reagent formed in each reaction was carried out by the method of Gorog and Szepesi⁴. The experimental results are shown in the table.