纯水中金属钕诱发芳香醛烯丙基化反应的研究

在Nd-SnCl₂-H₂O体系中, 用烯丙基溴超声诱发下进行了一系列芳香醛的烯丙基反应, 室温反应50～60 min得76%～93%烯丙基化产物; 而不用超声波时同样体系中搅拌3～4 h高烯丙基醇产率为30%～86%. 该方法时间短、产率高、环境友好.     

Allylation Reactions of Aromatic Aldehydes with Antimony in Aqueous Media Under Ultrasonic Irradiation

The allylation reactions of aromatic aldehydes with allyl bromide were carried out in 89–98% yield with Sb-H₂O-KF-CH₃OH under ultrasound irradiation at rt for 2.5 h. The reactions in the same system gave allylic alcohols in 30–69% yield with stirring for 24 h. The main advantages of the present procedure are shorter reaction time, better yield, and environmental friendliness.     

2,2'－联吡啶桥连的双－4,4'-联吡啶哑铃型化合物的合成

二甘醇2与对甲苯磺酰氯在CH_2Cl_2中，0 ℃～r.t.及Et_3N存在下反应得2－ （羟乙氧基）乙醇对甲苯磺酸酯（3），收率88％。化合物3与对叔丁基苯甲酰氯在 CH_2Cl_2中0～5 ℃及吡啶存在下反应得2－（对叔丁基苯甲酰氧基乙氧基）乙醇对 甲苯磺酸酯（4），收率96％。4与对羟苯甲醇在乙腈中及CsF/K_2CO_3存在下70 ℃ 反应得2－（对叔丁基苯甲酰氧基乙氧基）乙氧苄醇（5），收率98％。5与NBS及 PPh_3在THF中，室温下反应得化合物2－（对 丁基苯甲酰氧基乙氧基）乙氧苄溴 （6），收率95％。6与4,4'－联吡啶在乙腈中，60 ℃反应1h得N－[2－（对叔丁基 苯甲酰氧基乙氧基）乙氧苄基]－4,4'－联吡啶六氟磷酸盐（7），收率85％。7与 α,α－二（溴甲基）－2,2'－联吡啶在乙腈中，油浴60 ℃反应36h，得到标题化 合物，产率为45％。     

Studies on the Lanthanum‐Induced Pinacol Coupling of Aromatic Aldehydes and Ketones in Aqueous Media

The pinacol coupling of aromatic aldehydes and ketones was carried out in 16–71% yield using La–36%HAc–CH₂Cl₂ system with stirring at rt in 4 h. The reactions in the same system gave pinacols in 12–91% yield under ultrasound irradiation at rt in 2 h.     

Photochemistry of 4-(2'-aminoethyl)quinolones: enantioselective synthesis of tetracyclic tetrahydro-1aH-pyrido[4',3':2,3]- cyclobuta[1,2-c] quinoline-2,11(3H,8H)-diones by intra- and intermolecular [2 + 2]-photocycloaddition reactions in solution

Enantioselective [2 + 2]-photocycloaddition reactions on 4-(2'-aminoethyl)quinolones in solution were studied using the enantiomerically pure complexing agent 1 as source of chirality. The intermolecular reactions of fully N-protected substrates 5a-5c with different 2-alkyl-substituted acrylates 12-15 represent the first systematic study on the diastereoselectivity of their intermolecular [2 + 2]-photocycloadditions to unsymmetrically 1,1-disubstituted olefins (75-91% yield, d.r. = 58/42-95/5). N-Benzylic-protected photoproducts exo-16a/b-19a/b could easily be converted into lactams 20a/b-23a/b by a sequence of Boc deprotection and thermal lactamization (74-98% yield). Identical products 20a-22a were directly accessible by the intramolecular [2 + 2]-photocycloaddition of acrylic acid amides 2-4 (41-61% yield). The suitability of both pathways for an enantioselective reaction variant was proven (70-92% ee). Thus, tetracyclic lactams possessing the carbon framework C were obtained with good yields and enantioselectivities of up to 92% ee in intramolecular reactions. Comparative investigation of both routes showed that quinolone dimerization was the single most decisive factor preventing a complete chirality transfer. Functional group manipulations were successfully conducted with the primary photoproduct exo-17a. Finally, a new and unexpected type of benzylic hydrogen abstraction-radical cyclization reaction was discovered for substrate 5a, which explains the photochemical instability of substrates 2-5 under short wavelength irradiation (lambda = 300 nm).     

MMT/FeCl_3催化的α-羰基二硫缩烯酮与二苯甲醇的Friedel-Crafts烷基化反应

研究了MMT/FeCl_3催化α-羰基二硫缩烯酮与二苯甲醇的Friedel-Crafts烷基化反应,合成了22个二硫缩烯酮类化合物(3a~3v),其中3b,3d~3f,3h~3r和3t为新化合物,其结构经1H NMR和13C NMR表征。以3a的合成为例,对反应条件进行优化。结果表明:在最优反应条件[1-(1,3-二噻烷-2-亚甲基)-4-苯基-3-丁烯-2-酮(1a)0.25 mmol,二苯甲醇0.3 mmol,MMT/FeCl_315 mmol%,CH_2Cl_22 m L,回流反应2 h]下,3a产率93%;MMT/FeCl_3循环使用3次,收率基本维持不变。     

Regioselective Cycloaddition of the Dimethyl Ester of Acetylenedicarboxylic Acid to 2,4,6-Triazidopyridines

2,4,6-Triazido-3,5-dichloropyridine was obtained in the reaction of pentachloropyridine with sodium azide. At room temperature, this azide reacts regioslectively with norbornene at the -azide group to give the corresponding 4-(3-azatricyclo[3.2.1.0]octanyl)-2,6-diazidopyridine in 88% yield. The cycloaddition of the dimethyl ester of acetylenedicarboxylic acid to this triazide proceeds at the azide groups at C₍₂₎ and C₍₆₎ in the pyridine ring to give 4-azido-2,6-di(4',5'-dimethoxycarbonyl)-1H-1,2,3-triazolopyridine. The analogous reaction of 2,4,6-triazido-3,5-dicyanopyridine with the dimethyl ester of acetylenedicarboxylic acid stops at the formation of 2,4-diazido-6-(4',5'-dimethoxycarbonyl)-1H-1,2,3-triazolopyridine. In contrast to reactions with electron-rich dipolarophiles, the cycloaddition of electron-deficient dipolarophiles to 2,4,6-triazidopyridines proceeds with thermodynamic control primarily a! t the azide groups bearing the highest orbital density in the HOMO.     

Reaction of Red Phosphorus with 4-Methoxystyrene in KOH-DMSO System: One-Pot Synthesis of Tris[2-(4-methoxyphenyl)ethyl]phosphane Oxide

Abstract

Red phosphorus reacts with 4-methoxystyrene in the KOH-DMSO superbase system (130 °C, 3 h, Ar) in the presence of a small quantity of H₂O to give tris[2-(4-methoxyphenyl)ethyl]phosphane oxide as the main product in 30% yield. Microwave activation of the reaction (600 W, 6 min) affords basically a mixture of the phosphane oxide and tris[2-(4-methoxyphenyl)ethyl]phosphane (in a ratio of 1:1). When the mixture is exposed to air (r.t., 24 h), the phosphane oxide is formed in 85% yield.

GRAPHICAL ABSTRACT     

Production of 52Fe by the 55Mn(p,4n)52Fe reaction and milking of 52mMn from 52Fe

The excitation functions were measured for the nuclear reactions of 55Mn(p,4n)52Fe and 55Mn(p,n)55Fe by using thin manganese disks, specially prepared under a pressure of 200-250 kg/cm2 at 400-500 degrees C for 0.5-1 hour. The maximum cross section in the excitation function for the 55Mn(p,4n)52Fe reaction was found to be 1.4mb at Ep = 54 MeV. From the yield curve, 24.8 MBq/microA h (670 muCi/microA h) of 52Fe was estimated to be produced with 0.45% 55Fe contamination in the energy region between 73 and 39 MeV. Iron-52 was produced in the yield of 85-93% to the expected value from the yield curve in the energy region of 44-60 MeV. For the separation of 52Fe, the radiochemical yield of 52FeCl3 was 70-92% and its radionuclidic purity was higher than 99%. Manganese-52m was obtained repeatedly by eluting the anion exchange column adsorbing 52Fe with 6N-HC1 in 99.9% radionuclidic purity and 86% yield to the expected value. The amount of 55Fe in a large quantity of 52Fe could be determined in 1-2 days from end of bambardment (EOB) by analyzing decay curve of Mn-Ka-X ray from 52Fe and 55Fe.     

(CyPF-(t)Bu)PdCl2]: an air-stable, one-component, highly efficient catalyst for amination of heteroaryl and aryl halides

An air- and moisture-stable palladium catalyst, [(CyPF-(t)Bu)PdCl2] (1), for coupling of heteroaryl chlorides, bromides, and iodides with a variety of primary amines is described. Most of these reactions occurred in high yield with 0.001-0.05 mol % catalyst loading. The reactions tolerated a wide range of functional groups.     

Studies on the Allylation Reactions of Aldehydes and Ketones with Lanthanum in Water

The allylation reactions of aldehydes and ketones were carried out in 25%–98% (or 29%–96%) yield with La/SnCl₂/H₂O under ultrasound irradiation (or stirring) at rt for 1 h (or 4 h). The main advantage of the present procedure is the higher yield and the environmentally benign method.     

离子液体中聚乙二醇维生素E琥珀酸酯的合成

以离子液体为催化剂,由维生素E经两步酯化反应合成了聚乙二醇1000(PEG1000)维生素E琥珀酸酯。以离子液体1-(N',N'-二甲胺乙基)-3-甲基咪唑四氟硼酸盐为催化剂、1,2-二氯乙烷为助溶剂、维生素E与琥珀酸酐摩尔比为1:1.2,在80 ℃条件下反应4 h,维生素E琥珀酸酯(TAS)的产率为90%。以1-丙磺酸基-3-甲基咪唑硫酸氢盐/甲苯为反应体系,TAS与PEG1000摩尔比为1:2,在100 ℃下反应5 h,PEG1000维生素E琥珀酸酯(TPGS)收率为91%。     

Asymmetric strecker reaction of aldimines using aqueous potassium cyanide by phase-transfer catalysis of chiral quaternary ammonium salts with a tetranaphthyl backbone

The phase-transfer-catalyzed, highly enantioselective cyanation of aldimines using aqueous KCN has been realized based on the molecular design of chiral quaternary ammonium iodide 2c bearing a stereochemically defined tetranaphthyl backbone. For example, vigorous stirring of a mixture of cyclohexanecarboxaldimine (R = c-Hex) and (R,R,R)-2c (1 mol %) in toluene-KCN aqueous solution (1.5 equiv) at 0 degrees C for 2 h gave rise to the corresponding protected amino nitrile (R = c-Hex) in 89% yield with 95% ee. A wide range of aliphatic aldimines, including those having alpha-tert-alkyl substituents, is tolerated by the present system. This study represents a novel approach for the asymmetric Strecker-type reactions, which utilizes chiral phase-transfer catalysts for practical access to various unusual, optically pure alpha-amino acids.     

功能化离子液体室温催化合成乙酸苄酯

制备了N-甲基-N′-磺酸烷基-咪唑阴离子型功能化室温离子液体,研究了功能化室温离子液体(TSILs)于室温下催化乙酸和苯甲醇反应合成乙酸苄酯的新方法,考察了多种TSILs的催化性能。结果表明,所合成的TSILs具有很高的催化活性,乙酸和苯甲醇的摩尔比为1:1．3,在室温下反应2．5 h,乙酸苄酯的产率可达92％,选择性超过99％。由于生成的乙酸苄酯不溶于催化体系,反应产物与催化体系分层,通过简单的倾析便可实现产物分离,简化了分离过程。离子液体可以循环使用,而其催化活性没有明显降低。     

Efficient conversion of tomatidine into neuritogenic pregnane derivative

Moderate acetylation of tomatidine with anhydrous acetic acid and pyridine for 20 h at r.t., followed by pseudomerization in ice-water, gave a delta(20(22))-pseudo compound, which was then subjected to ozonolysis to provide a pregnane derivative in a total 54% yield showing neuritogenic and NGF-enhancing activities.     

Addition reaction of 2-phenylbenzoic acid onto unactivated olefins catalyzed by Ru(II)-xantphos catalysis

Ru(II)-xantphos catalysis is found to be effective for the addition reaction of 2-phenylbenzoic acid onto unactivated olefins. Thus, the reactions of 2-phenylbenzoic acid and unactivated olefins are carried out in the presence of 5 mol % of Ru(II)-xantphos catalysis in refluxing CHCl₃ for 48 h to afford the corresponding esters in 40-95% yield. The control experiments indicate that the influence of TfOH for Brønsted acid catalyst was vanishingly small in our new catalytic system.     

Aromatic amino-claisen rearrangement in the synthesis of ellipticine

A convenient route is described for the preparation of 1,4-dimethylcarbazole — the key compound in the synthesis of the antitumoral alkaloid ellipticine. The interaction of 2,5-xylidine with 3-chlorocyclohexene led to N-(cyclohex-2-enyl)-2,5-xylidine (I), the two-hour heating of which at 140–150°C gave the product of an amino-Claisen rearrangement, 6-(cyclohex-2-enyl)-2,5-xylidine (II) with a yield of 82%. The intramolecular cyclization of compound (II) in polyphosphoric acid (130–140°C, 5 h) led to 5,6,7,8,12,13-hexahydro-1,4-dimethylcarbazole (III) in a yield of 75%. The dehydrogenation of substance (III) by boiling in trimethylbenzene in the presence of Pd/C gave 1,4-dimethylcarbazole (IV) with a yield of 87%. The conditions for performing the reactions and the physicochemical constants of the compounds obtained are given.     

PINACOL COUPLING OF AROMATIC ALDEHYDES AND KETONES USING MAGNESIUM IN AQUEOUS AMMONIUM CHLORIDE UNDER ULTRASOUND

ABSTRACT

The pinacol coupling reaction of aromatic aldehydes and ketones was performed in 8–95% yield with magnesium in 0.1 M aqueous NH₄Cl under ultrasound irradiation at r.t. for 3 h.     

Rhodium N-heterocyclic carbene-catalyzed [4 + 2] and [5 + 2] cycloaddition reactions

[reactions: see text] A rhodium complex of N-heterocyclic carbene (NHC) has been developed for intra- and intermolecular [4 + 2] and intramolecular [5 + 2] cycloaddition reactions. This is the first use of a transition-metal NHC complex in a Diels-Alder-type reaction. For the intramolecular [4 + 2] cycloaddition reactions, all the dienynes studied were converted to their corresponding cycloadducts in 91-99% yields within 10 min. Moreover, up to 1900 turnovers have been obtained for the intramolecular [4 + 2] cycloaddition at 15-20 degrees C. For the intermolecular [4 + 2] cycloadditions, high yields (71-99%) of the corresponding cycloaddition products were obtained. The reaction time and yield were highly dependent upon the diene and the dienophile. For the intramolecular [5 + 2] cycloaddition reactions, all the alkyne vinylcyclopropanes studied were converted to their corresponding cycloadducts in 91-98% yields within 10 min. However, the catalytic system was not effective for an intermolecular [5 + 2] cycloaddition reaction.     

An improved catalyst for the asymmetric arylation of ketone enolates

A new catalyst system for the enantioselective alpha-arylation of ketones is reported. This catalyst, prepared from Pd(2)(dba)(3) and a bulky dialkylphosphino-binaphthyl ligand, is able to effect the asymmetric arylation of ketone enolates with aryl bromides utilizing NaO(t)()Bu as base. These new catalysts enjoy much higher reactivity than previous systems; arylation reactions could be effected at room temperature with only 2 mol % of the Pd catalyst. The coupling of alpha-alkyl-alpha'-protected cyclopentanones proceeded in high yield, and the resulting quaternary stereogenic center was installed in up to 94% ee.