Synthesis of new tetracyclic azaheteroaromatic cores via auto-tandem Pd-catalyzed and one-pot Pd- and Cu-catalyzed double C-N bond formation

Inter- and intramolecular transition metal-catalyzed amination of 2-chloro-3-iodopyridine and 2,3-dibromopyridine, respectively, with benzodiazinamines yielded six hitherto unknown tetracyclic azaheteroaromatic cores. C-N bond formation was achieved via auto-tandem (Pd-catalyst) as well as one-pot (sequential use of a Pd- and Cu-catalyst) catalysis.     

A convenient one-pot synthesis of boroxoles from diboronic acid

The preparation of the boroxole motif traditionally relies on a 3-step process and the use of n-butyl lithium that can limit substrate scope. Herein during our exploration toward novel RORγ inhibitors, we identified a convenient one-pot preparation of the motif in good yields with good substrate scope.     

铜催化芳香醛和酮的氢硼化转化合成苄基硼酸酯类化合物（英文）

有机硼化合物广泛应用于合成化学、药物化学以及材料化学等领域,开发新颖实用的方法合成有机硼化合物是重要的研究领域.在各种有机硼化合物中,苄基硼酸酯有着一些特有的性质,例如活性相对较高,可以有效地当作苄基化试剂使用.目前已有多种合成苄基硼酸酯的方法,主要集中在苄基格氏试剂或者锂试剂的硼化反应,但是该方法底物兼容性较差,而且苄基格氏试剂或者锂试剂的制备比较困难.随着催化反应的发展,过渡金属(如Pd,Cu,Ni,Fe)催化苄基卤代物的硼化反应及芳基卤代物和1,1-二硼类化合物的偶联反应能够有效地合成这类化合物.一级苄醇在钯或铜的催化作用下也可以转化为苄基硼酸酯.苄基C–H键的催化硼化是潜在的构建苄基硼酸酯的高原子经济性的方法,但目前其选择性和反应活性仍不高.在无金属催化的条件下,对甲苯磺酰腙类化合物与HBpin或B_(2pin_2)发生1,2-金属迁移是合成苄基硼酸酯的有效方法.到目前为止,虽然有很多种合成苄基硼酸酯的方法,但仍无法满足其合成需求,因此开发新型的方法合成苄基硼酸酯具有重要的意义.本文开发了一种新型的铜催化芳香醛/酮类化合物的脱氧氢硼化转化体系.使用廉价易得的铜作为催化剂,叔丁醇钠或者叔丁醇钾作为碱,醇质子作为氢源,在100℃的条件下,芳香醛和芳香酮可直接转化成一级和二级苄基硼酸酯类化合物,该反应操作简单,反应体系可以兼容多种官能团,分离产率在21%–77%之间.反应机理方面,该转化有两种可能的过程,(1)反应体系中首先生成1,1-偕二硼化合物,该化合物在碱和EtOH的作用下发生脱硼质子解,最终转化成苄基单硼化合物;(2)醇质子转化成负氢物种,并与体系中的冄-OBpin硼酸酯生成四配位硼,发生1,2-迁移后得到目标产物.为了验证上述两种反应途径的可行性,我们进行了一系列的控制试验.首先合成了苯乙酮的1,1-二硼化合物,在催化量碱与当量醇的作用下,以99%的收率得到了脱硼质子解的产物,说明1,1-二硼化合物可以在反应体系中转化成苄基单硼化合物.以苯甲醛作为原料合成了冄-OBpin硼酸酯,首先将其投入到甲醇、叔丁醇钠和B_(2pin_2)的体系中,最终得到了47%的苄基单硼;同时将冄-OBpin硼酸酯投入到HBpin与叔丁醇钠的体系中,得到了57%的苄基单硼化合物,说明第二种反应过程通过1,2-迁移得到目标产物也是可行的.在当前的实验条件下,两种反应路径都是可能的.     

Copper-catalyzed aryl amination in aqueous media with 2-dimethylaminoethanol ligand

Copper-catalyzed amination of aryl bromides and iodides under mild conditions has been developed with 2-dimethylaminoethanol as ligand and water as solvent. A variety of hydrophilic and hydrophobic aryl halide substrates have been aminated in good yield with a variety of amino acids, amino alcohols and peptides. This method has successfully N-arylated some hydrophilic amino compounds not available by other methods.     

A simple method for the synthesis of 4-arylselanyl-7-chloroquinolines used as in vitro acetylcholinesterase inhibitors and in vivo memory improvement

We described here an alternative method for the synthesis of 4-arylselanyl-7-chloroquinolines through reactions of 4,7-dichloroquinoline with organylselenols, generated in situ by the reaction of diorganyl diselenides with H₃PO₂ (50 wt% in H₂O). These reactions proceeded efficiently at 60 °C under N₂ atmosphere and are suitable to a range of diorganyl diselenides containing electron-donating and electron-withdrawing groups, affording the corresponding 4-aryl-7-chloroquinolines in high yields. The synthesized compounds were screened for their in vitro acetylcholinesterase (AChE) activity and our results demonstrated that the 7-chloro-4-[(4-fluorophenyl)selanyl]quinoline inhibited the AChE activity and improved memory in mice, making this compound is a potential therapeutic agent for the treatment of Alzheimer disease and other neurodegenerative disorders.     

A one-pot,two-step synthesis of 3-deazacanthin-4-ones via sequential Pd-catalyzed Suzuki-Miyaura and Cu-catalyzed Buchwald-Hartwig reactions

3-Deazacanthin-4-one and nine analogues, including the 8-aza analogue, were prepared rapidly and in high yields from 8-iodoquinolones and 2-chloro(het)arylboronic acids. The strategy involves construction of the central B ring via concomitant Pd-catalyzed Suzuki-Miyaura CC and Cu-catalyzed Buchwald-Hartwig CN coupling reactions.     

Enantioselective synthesis of N-heterocycles via intramolecular Pd(0)-catalysed allylic amination

An efficient and stereoselective synthesis of pyrrolidine-, piperidine-, and azepane-type N-heterocycles is described by the intramolecular Pd(0)-catalysed cyclisation of amino allylic carbonates. The use of chiral ligands gave the corresponding heterocyclic derivatives having er values that were from moderate to good.     

Simple manganese carbonyl catalyzed hydrogenation of quinolines and imines

Manganese-catalyzed hydrogenation of unsaturated molecules has made tremendous progresses recently benefiting from non-innocent pincer or bidentate ligands for manganese. Herein, we describe the hydrogenation of quinolines and imines catalyzed by simple manganese carbonyls, Mn₂(CO)₁₀ or MnBr(CO)₅, thus eliminating the prerequisite pincer-type or bidentate ligands.     

Metal-free one-pot three-step process for the direct conversion of aryl alkynes into secondary amines with TfOH/B2(OH)4

A metal-free one-pot synthesis of secondary amines from aryl alkynes via hydration-condensation-reduction three-step process in the presence of TfOH and B₂(OH)₄ has been developed. A series of secondary amines were obtained with good functional group tolerance and satisfied yields.     

New active-iron based reducing system for carbonyl compounds and imines. Stereoselective reduction of cyclic ketones

The reaction of different carbonyl compounds and imines with a mixture of iron(II) chloride tetrahydrate, an excess of lithium powder, and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol%) in THF at room temperature, led to the formation of the corresponding alcohols and amines, respectively. The process was also applied to the transformation of α,β-unsaturated carbonyl compounds into the corresponding saturated alcohols. The new reducing system exhibited good to excellent diastereoselectivity toward the reduction of different monocyclic and polycyclic ketones.     

4,4’-trimethylenedipiperidine as a nitrogen heterocycle solvent and/or catalyst: Liquid phase tandem Knoevenagel–Michael condensation

Liquid phase tandem Knoevenagel–Michael condensation of various aromatic and heteroaromatic aldehydes with barbituric acid or 2-thiobarbituric acid and malononitrile was studied in a one-pot three-component reaction. For the first time, TMDP was employed as a safe and efficient solvent and/or catalyst in the liquid and aqueous ethanol medium, respectively, for the practical and eco-friendly Knoevenagel–Michael condensation. The reactions were carried out by using greener procedures, including a) the use of TMDP as an N-heterocycle organocatalyst in a green medium including water and ethanol (1:1 v/v) at reflux temperature, and b) the use of TMDP as a dual solvent-catalyst at 65 °C in the absence of any solvent. High to excellent yields of the desired pyrano[2,3- d ]pyrimidinones were obtained under the two earlier mentioned conditions. The current methodologies have advantages, including (a) avoiding hazardous, toxic, volatile, and flammable materials and solvents, (b) avoiding tedious processes, harsh conditions, and multiple steps for the preparation of catalysts, (c) using a less toxic and noncorrosive catalyst, (d) minimizing hazardous waste generation and simple workup process, and (e) high recyclability of TMDP. Another important result of this work is that the TMDP can be a promising alternative for toxic, volatile, and flammable base reagents such as piperidine and triethylamine in liquid phase organic syntheses owing to its unique properties such as being less toxic, nonflammable, and nonvolatile, and having a low melting point, broad liquid range temperature, high thermal stability, and safe handling and storage.     

Hydroformylation of Internal Olefins to Linear Aldehydes with Novel Rhodium Catalysts

Unprecedented high activities and selectivities were observed in the hydroformylation of internal octenes to linear products using rhodium catalysts with rigid diphosphane ligands. Dibenzophosphole 1 and a phenoxaphosphane analogue with bite angles of 120 and 119°, respectively, are suited for this.     

Copper(I)‐Catalyzed Amination of Halogenopyridines with Polyamines

Cu^I‐Catalyzed amination of 2‐bromo‐, and 2‐, 3‐, and 4‐iodopyridines with tri‐ and tetraamines aimed at the synthesis of N,N′‐diheteroaryl derivatives was studied. A strong dependence of the product yields on the nature of starting compounds and the ligand used was observed. The increase in the number of ethene‐1,2‐diamine fragments in the polyamine structure led to the increase in the yields of polyheteroarylated compounds, whereas propane‐1,3‐diamine fragments favored the formation of monopyridinyl derivatives and promoted the heteroarylation of the secondary amino groups. 2‐Iodopyridine, as a more reactive compound, readily formed N,N‐diarylated products. The best yields of the target N,N′‐dipyridin‐2‐yl derivatives were 76% in the case of the triamine and 68% in the case of the tetraamine. A comparison of Cu^I‐ and Pd⁰‐mediated heteroarylation of polyamines was also presented.     

Sulfamic acid catalysed synthesis of pyranocoumarins in aqueous media

An efficient, one pot synthesis of pyranocoumarins by the condensation of 4-chloro-3-formylcoumarin with different active methylene compounds via Knoevenagel, Michael and cyclization sequences under homogeneous catalytic conditions using sulfamic acid in aqueous media is reported. The catalyst is found to be active for four cycles.     

Cu-catalyzed aerobic oxidative synthesis of sulfonamides from sulfonyl hydrazides and amines

An environmentally friendly route for sulfonamides has been developed. The oxidative coupling of sulfonyl hydrazides and amines was catalyzed by CuBr₂ to produce various sulfonamides with the water and nitrogen gas as byproducts. Preliminary experiments revealed that the sulfonyl radical is likely to be involved in the reaction mechanism.     

均相催化CO2/H2还原羰基化合成高值化学品研究进展

The efficient utilization of the greenhouse gas CO₂ as a C1 feedstock can effectively reduce its emission and create economic value. Hence, the efficient chemical conversion of CO₂ has been receiving intense attention. Due to the extremely low energy level of the CO₂ molecule, the high energy barrier is the primary challenge for the chemical conversion of CO₂. The chemical conversion of CO₂ is mainly carried out through non-reductive transformation in industrial. Yet, the new route of chemical synthesis based on CO₂ reductive transformation is an interesting topic to expand its resource utilization. In this context, homogeneous reductive carbonylation is a hot topic for the utilization of CO₂ via reductive transformation. In this process, the metal hydride intermediate derived from the activation of the hydrogen source is crucial to the CO₂ reduction. Hydrogen, a clean source with high atom economy, can be used as a reducing agent for the reductive conversion of inert CO₂ through carbonylation, to construct C―O, C―N, and C―C bonds and to synthesize aldehyde/alcohol, carboxylic acid, ester, amide, and other chemicals. These expand the scope of CO₂ high-value utilization and show great potential application in terms of resource utilization and environmental protection. This CO₂ utilization process is thought to involve cascading catalytic reactions of CO₂ reduction and carbonylation. The catalytic systems require the corresponding catalysts to efficiently promote each step and effectively inhibit undesired side reactions. Recently, considerable progress has been made in the homogeneous reductive carbonylation of CO₂ with H₂. However, this kind of reaction is mostly of the cascade type, and hence, requires harsh conditions and noble metal catalysts. The chemoselectivity is low because of the multiple competing reactions. In addition, due to the steric hindrance and electronic effects of the substrate, there are limitations on the types of substrates that can be employed. With the development of new characterization techniques and theoretical calculations, some progress has been made in revealing the reaction mechanism and in the activation of the carbon-oxygen bonds of CO₂. Therefore, there is an urgent need to develop a more efficient catalytic system that requires mild conditions for reductive carbonylation. In this review, we provide an overview of the groundbreaking studies and the recent breakthroughs that have demonstrated the potential of metal catalysts to utilize the combination of CO₂ and H₂ as a C1 synthon, including olefin carbonylation, amine carbonylation, and alcohol/ether carbonylation, while highlighting the effect of different types of metal catalysts on the reaction. We conclude with a perspective on the future prospects of the homogeneous reductive carbonylation of CO₂ with H₂, providing readers a snapshot of this rapidly evolving field.     

Copper(II) Halide Complexes with 1‐tert‐Butyl‐1H‐1,2,4‐triazole and 1‐tert‐Butyl‐1H‐tetrazole

1‐tert‐Butyl‐1H‐1,2,4‐triazole (tbtr) was found to react with copper(II) chloride or bromide to give the complexes [Cu(tbtr)₂X₂]_n and [Cu(tbtr)₄X₂] (X = Cl, Br). 1‐tert‐Butyl‐1H‐tetrazole (tbtt) reacts with copper(II) bromide resulting in the formation of the complex [Cu₃(tbtt)₆Br₆]. The obtained crystalline complexes as well as free ligand tbtr were characterized by elemental analysis, IR spectroscopy, thermal and X‐ray analyses. For free ligand tbtr, ¹H NMR and ¹³C NMR spectra were also recorded. In all the complexes, tbtr and tbtt act as monodentate ligands coordinated by Cu^II cations via the heteroring N⁴ atoms. The triazole complexes [Cu(tbtr)₂Cl₂]_n and [Cu(tbtr)₂Br₂]_n are isotypic, being 1D coordination polymers, formed at the expense of single halide bridges between neighboring copper(II) cations. The isotypic complexes [Cu(tbtr)₄Cl₂] and [Cu(tbtr)₄Br₂] reveal mononuclear centrosymmetric structure, with octahedral coordination of Cu^II cations. The tetrazole compound [Cu₃(tbtt)₆Br₆] is a linear trinuclear complex, in which neighboring copper(II) cations are linked by single bromide bridges.     

Microwave mediated reduction of heterocycle and fluorine containing nitroaromatics with Mo(CO)6 and DBU

Heterocycle containing nitroaromatics were reduced by Mo(CO)₆ and DBU in EtOH under microwave irradiation within 15 min. Under the same conditions, 4-fluoronitrobenzene was reduced to 4-fluoroaniline, whereas 2-chloro-1-fluoro-4-nitrobenzene afforded a mixture of 3-chloro-4-fluoroaniline and 3-chloro-4-ethoxyaniline. The extent of the competing S_NAr/reduction process could be influenced by the nature of the solvent, with t-BuOH the inert solvent of choice. The latter was used as solvent for S_NAr/reductions of 2-chloro-1-fluoro-4-nitrobenzene with S-nucleophiles to yield 3-chloro-4-mercaptoanilines.     

聚烷基紫精电解质复合物催化偶氮苯的还原研究

本文报道了几种聚烷基紫精复合物的制备, 并研究了作为电子转移催化剂在偶氮苯还原中的作用, 结果显示,聚烷基紫精-聚阴离子复合物具有诱导偶氮苯还原的能力.并且不同聚电解质复合物具有不同的电子转移中介能力.     

Halido-bridged Copper(II) Complexes with 1-tert-Butyl-1H-tetrazole: Crystal Structure and Magnetic Properties

Complex [Cu(tbt)Cl₂]_n (tbt = 1-tert-butyl-1H-tetrazole) was prepared by reaction of tbt with copper(II) chloride in solution. According to single-crystal X-ray analysis, this complex presents 1D coordination polymer, formed at the expense of double chlorido bridges between neighboring pentacoordinate copper(II) cations. 1-tert-Butyl-1H-tetrazole acts as monodentate ligand coordinated by Cu^II cations via the heteroring N⁴ atoms. The temperature-dependent magnetic susceptibility measurements of novel complex [Cu(tbt)Cl₂]_n as well as described previously 1D coordination polymer [Cu(tbt)₂Cl₂]_n, and linear trinuclear complex [Cu₃(tbt)₆Br₆], were carried out. Magnetic studies revealed that the copper(II) ions were weakly ferromagnetically coupled in polymeric copper(II) chloride complexes, whereas complex [Cu₃(tbt)₆Br₆] showed antiferromagnetic coupling.