Iron oxide colloids and their heterogenization by silica sol–gel entrapment: Catalytic and magnetic properties

Fe₃O₄ colloids modified by the chiral ligand cinchonidine were prepared with the goal of obtaining a magnetic and catalytic nano-material and were subsequently embedded in silica to form a heterogeneous catalyst. The systems were characterized by TEM and XRD measurements, while the Mössbauer technique was applied for measuring the magnetic properties of the Fe₃O₄ colloids. The hyperfine magnetic field distribution was consistent with one type of Fe oxide, namely, the magnetite (Fe₃O₄). These colloids, both as ‘quasi-homogenous catalysts’ (or soluble heterogeneous catalysts) and embedded in silica (heterogeneous catalysts) were employed in the selective hydrogenolysis of complex bicyclo[2.2.2]oct-7-enes (bicyclo[2.2.2]oct-2-enes when unsubstituted).     

A Versatile Synthetic Platform Based on Bicyclo[4.1.0]heptenes

Bicyclo[4.1.0]heptenes, which are readily accessible molecules via the transition metal-catalyzed cycloisomerization of 1,6-enynes, and have served as useful building blocks in organic synthesis. These molecules can undergo a variety of ring-opening reactions given that the release of the cyclopropyl ring strain (27.5 kcal/mol) may serve as a thermodynamic driving force for reactions, and the double bond within the skeleton can afford the kinetic opportunity to initiate the ring-opening via a coordination to a metal species. Even though the chemistry of the cyclopropyl group has been widely explored in organic chemistry, less attention has been paid to the chemistry of bicyclo[4.1.0]heptenes. However, during the past 5 years, we have been engaged in the exploration of the chemistry of bicyclo[4.1.0]heptenes. This review describes the chemistry developed in our laboratory. Depending upon the position, number, and identity of the substituent(s), the identity of the tether group, and the nature of the catalytic system, bicyclo[4.1.0]heptenes can undergo a variety of transformations. Our studies have revealed the reaction patterns of bicyclo[4.1.0]heptenes which include thermal reactions, nucleophilic addition, and rhodium-catalyzed reactions, that can proceed both with and without opening of the cyclopropyl ring. The chemistry described in this review can be used to produce a variety of new compounds such as 2,4-pentadienals, 3-methylene-4-vinylcyclohex-1-enes, bicyclo[3.2.2]nonadienes, 1,6,7,9a-tetrahydrocyclohepta[c] pyrans and -pyridines, hexahydroisoquinolines, 4-oxa-6-azatricyclo[3.3.0.0^2,8]octanes, and heterotricyclo[3.3.1.0^2,8]nonanes.     

North‐ and South‐Bicyclo[3.1.0]Hexene Nucleosides: The Effect of Ring Planarity on Anti‐HIV Activity

The syntheses of new conformationally locked North‐ and South‐bicyclo[3.1.0]hexene nucleosides is reported. The North analogues were synthesized by a convergent approach from the known (1S,2R,5R)‐5‐[(tert‐butyldiphenylsilyloxy)methyl]bicyclo[3.1.0]hex‐3‐en‐2‐ol by Mitsunobu coupling with the nucleobases. The South analogues were synthesized from their bicyclo[3.1.0]hexane nucleoside precursors by the selective protection of the primary hydroxy group, conversion of the secondary alcohol into a good leaving group, and base‐catalyzed elimination to generate the olefin. The transformation of a bicyclo[3.1.0]hexane nucleoside into a bicyclo[3.1.0]hexene nucleoside flattens the five‐membered ring of the bicyclic system and rescues anti‐HIV activity for North‐D4T, North‐D4A, and South‐D4C. The relationship between planarity and the anti/syn disposition of the nucleobase that is favored by a particular pseudosugar platform are proposed as key parameters in controlling biological activity.     

Gold‐Catalyzed Synthesis of Bicyclo[3.2.0]heptenes via a Formal [3+2]/[2+2]‐Annulation of Allylsilane with 4‐Methoxybut‐2‐yn‐1‐ols

This work reports the novel gold‐catalyzed [3+2]/[2+2]‐annulation of allylsilane with 4‐methoxybut‐2‐yn‐1‐ols that yields highly strained bicyclo[3.2.0]heptene products efficiently and stereoselectively.     

二环[2.2.1]庚烷-2,3-二羧酸二钠的合成及表征

以用量为原料质量24.33％的380～830?μm的Raney?Ni为催化剂,在常温常压条件下对二环[2.2.1]庚-5-烯-2,3-二羧酸二钠进行加氢,反应时间90?min,得到聚丙烯成核剂二环[2.2.1]庚烷-2,3-二羧酸二钠,收率达90％以上.在同样条件下,将50％(w)的再生催化剂与50％(w)的新鲜催化剂...     

Über die Autoxydation von Norbornenderivaten

On the Autoxidation of Derivatives of Norbornenen Norbornene, bicyclo[2, 2, 1]2-heptene-5-carboxylic acid methyl ester, bicyclo-[2, 2, 1]2-heptene-5-carbonitril, 5-methylbicyclo[2, 2, 1]2-heptene-5-carboxylic acid methyl ester and dicyclopentadiene are easily oxidized by molecular oxygen; the corresponding exo-epoxides are formed as main products by attack on the norbornene double bond.     

Zur Heck-Reaktion von 1-Chloralk-1-inen – Synthese und Charakterisierung von 1,3-disubstituierten 7-(Prop-2-inyliden)bicyclo[2.2.1]heptanen und anderen Bicyclen

The Heck reaction of cyclohexene with 1-chloroalk-1-ynes ClC≡CR 1 (R = Ph a , c-Hex b , n-Bu c , n-Oct d ) using [Pd(OAc)₂]/NaO₂CH/[NEt₃Bz]Cl as catalyst system (DMF, 25 °C) affords 1,3-disubstituted 7-(prop-2-ynylidene)bicyclo[2.2.1]heptanes 2 as tandem products by reaction of cyclohexene and ClC≡CR in a ratio of 1:2. To a smaller extent, substituted 7-[(cyclohexenyl)methylidene]bicyclo-[2.2.1]heptanes 3 (tandem products by reaction of cyclohexene and ClC≡CR in a ratio of 2:1) and the regular Heck products (alkynylcyclohexenes 4 ) are formed. The homocoupling of 1 to give RC≡C–C≡CR does not take place, except for R = n-Oct where it proceeds as side reaction. The analogous reaction of ClC≡CR with cycloheptene affords the 2:1 products (substitued 8-[(cycloheptenyl)methylidene]biyclo[3.2.1]octanes 6 ) as main products and the 1:2 products (1,3-disubstituted 7-(prop-2-ynylidene)bicyclo[3.2.1]-octanes 5 ) as well as the regular Heck products (alkynylcycloheptenes 7 ) as side products. The ratio 5 : 6 is strongly influenced by the ratio cycloheptene : 1 . The products 2 , 5a and 6 were isolated and characterized by means of ¹H and ¹³C NMR spectroscopy. The molecular structures of 7-(1,3-diphenylprop-2-ynylidene)bicyclo[2.2.1]heptane ( 2a ) and 8-[(cyclo-heptenyl)phenylmethylidene)]bicyclo[3.2.1]octane ( 6a ) (as mixture of the cyclohept-3- and -4-enyl double bond isomers) were determined by single-crystal X-ray structure analysis.     

聚丙烯成核剂双环[2.2.1]-庚烷-2,3-二羧酸钠的合成

以降冰片烯二酸酐为起始原料, 经水解中和和催化加氢制备了双环[2.2.1]-庚烷-2,3-二羧酸钠。通过研究催化加氢步骤中催化剂种类、催化剂用量、反应温度和反应压力等关键因素对双环[2.2.1]-庚烷-2,3-二羧酸钠的收率和纯度的影响, 获得了适宜的反应条件。实验结果表明:催化剂雷尼镍可代替文献报道的价格昂贵的钯/炭催化剂完成催化加氢反应, 在反应温度为60℃、反应压力为5MPa的条件下进行催化加氢, 双环[2.2.1]-庚烷-2,3-二羧酸钠的收率大于95%;红外光谱及核磁共振分析表明, 所得加氢产物与双环[2.2.1]-庚烷-2,3-二羧酸钠结构特征吻合。     

Masked o-benzoquinones in organic synthesis

An account of the synthetic utility of masked o-benzoquinones is provided. The inter- and intramolecular Diels-Alder reactions of in situ generated masked o-benzoquinones produced cycloadducts in excellent selectivities. New synthetic methodologies have been developed for the synthesis of highly substituted ring systems including bicyclo[2.2.2]octenones, oxatricycles, triquinanes, polysubstituted cyclohexanes, and bicyclo[4.2.2]decenones with complete stereocontrol from easily accessible 2-methoxyphenols via the Diels-Alder reaction of masked o-benzoquinones. Other reactions of adducts derived from masked o-benzoquinones are also described. The efficacy of our methodology is demonstrated by several examples of the total synthesis of natural products.     

Isomerizations of Cycloheptane to Methylcyclohexane and Cyclooctane to Ethylcyclohexane Catalyzed by Sulfated Zirconia

Reactions of cycloheptane and cyclooctane were performed over the superacid of sulfated zirconia in liquid phase at 50 °C a main product was methylcyclohexane from cycloheptane through a protonated bicyclo[4.1.0]heptane and ethylcyclohexane from cyclooctane via a protonated bicyclo[4.2.0]octane. Cyclodecane was dehydrogenated into decalines; cyclododecane was converted into many products, more than 30 species.     

水稻田用芽后除草剂双环磺草酮的合成研究

提出了以降冰片烯为原料合成关键中间体双环[3,2,1]辛烷-2,4-二酮,进一步合成除草剂双环磺草酮原药的工艺技术,并对此合成路线进行了初步研究.     

Gold(I)‐Catalyzed [4+2] Annelation/Nucleophilic Addition Sequence: Stereoselective Synthesis of Functionalized Bicyclo[4.3.0]nonenes

The gold(I)‐catalyzed isomerization of readily available 1,8‐dien‐4‐ynes allows the rapid construction of a variety of synthetically useful bicyclo[4.3.0]nonenes by a stereoselective sequence involving a [4+2] annelation/nucleophilic addition process.     

4-羟基-5(4′-氯苯基)双环[4,4,0]-1-氮杂癸烷的合成

以 4′ 氯哌醋甲酯为原料,研究了作为潜在的治疗可卡因滥用症的药物———4 羟基- 5- (4′- 氯苯基 )双环 [4,4, 0]- 1 氮杂癸烷的合成。4′- 氯哌醋甲酯首先用乙酸酐在室温下进行乙酰基化,然后在 -70℃下经二异丙基胺锂(LDA)作用关环得中间产物(±)- threo -2, 4 -二氧代- 5- (4′- 氯苯基)双环[4, 4, 0] -1 氮杂癸烷,产率 60%。中间体先用硼氢化钠在甲醇中室温下选择性地将酮羰基还原,粗产物经V(石油醚)∶V(乙酸乙酯) =1∶1重结晶后,在四氢呋喃中于回流温度下用乙硼烷 四氢呋喃络合物进一步还原酰胺基,得到(±) threo 4α 羟基- 5 -(4′- 氯苯基 )双环[4, 4, 0]- 1 氮杂癸烷,两步产率为 67%。所得α位羟基产物经过Swern氧化,然后在四氢呋喃中在 -78℃下用三(仲丁基)硼氢化钾选择性还原,立体专一性地得到 (±) threo- 4β 羟基- 5 (4′- 氯苯基 )双环 [4, 4, 0]- 1 氮杂癸烷,氧化 还原反应总产率为 70%。     

UNIFAC模型预测含α-蒎烯体系的汽液平衡数据

α-蒎烯具有一个特殊的双环双键结构。为更准确地预测含α-蒎烯体系的汽液平衡数据,利用UNIFAC模型原理对α-蒎烯进行基团重新划分,可得到一个大基团双环[3.1.1]-2-庚烯基与3个CH₃。通过对含α-蒎烯二元汽液平衡数据进行拟合,得到新基团双环[3.1.1]-2-庚烯基与CH₃、C=C、ACH、ACCH₃基团间的相互作用参数,扩大了UNIFAC模型的应用范围。与原始UNIFAC模型仅利用CH₃、C=C、ACH、ACCH₃基团预测出的含α-蒎烯三元体系汽液平衡数据进行比较,新基团模型预测的气相组成平均偏差以及温度平均偏差比原始基团模型的偏差要更小,说明新基团的划分更为合理。     

Addition polymerisation vs. ROMP on cyclic and strained olefins with the Mo(CO)5PPh3/alkylaluminums catalysts

The polymerisation of cyclic and strained monomers such as bicyclo[2.2.1]hept-2-ene (norbornene, NBE) and bicyclo[2.2.1]hepta-2,5-diene (norbornadiene, NBDE) with the catalytic systems Mo(CO)₅PPh₃/alkylaluminums was studied. From the polymers produced we demonstrate the existence of an antagonism between the ROMP (Ring-Opening-Metathesis-Polymerisation) mecanism and the olefin addition polymerisation mecanism. In addition ROMP mecanism is affected by the solvent. These catalysts also promotes the isomerisation of double bonds, as indicated by the ESR signal observed for the conjugated crosslinked polyNBDE produced by ROMP. Received: 5 August 1996/Revised version: 22 October 1996/Accepted: 25 October 1996     

Synthesis and properties of polyesterimides containing a bicyclo-octene ring

New polyesterimides containing a bicyclo-octene ring were synthesized by the polycondensation reaction of N,N′-dicarboxymethyl(bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid diimide)dimethylester and N,N′-dicarboxyphenyl(bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid diimide)dimethylester with various aliphatic diols. These polymers thus obtained are soluble in m-cresol, dimethylformamide (DMF), dimethylacetamide (DMAc) and dimethylsulfoxide (DMSO) except those from ethylene glycol. The polymers showed thermal stability above 350°C.     

分子光化学贮存太阳能 III.双环[2,2,1]-2,5-庚二烯的光诱导电子转移敏化异构化反应

以N,N,N′,N′-四甲基联苯二胺、2,6-二甲氧基萘和2,7-二甲氧基萘为光敏剂,在正己烷溶液中实现了双环[2,2,1]-2,5-庚二烯到四环[2,2,1,0~(2,6),0.(3,5)]庚烷的异构化。测定了反应的量子产率。讨论了反应机理。通过激发态的光敏剂与二烯之间的电子转移反应,形成单重态和三重态处于平衡状态的离子自由基对中间体。处于溶剂笼中的三重态离子自由基对经电子反传,产生激发三重态二烯。最后该激发态二烯经分子内[2+2]环合加成反应异构化为四环烷。     

Anti-bredt monomers

Summary 1-Aza-3-oxabicyclo[3.3.1]nonan-2-one, an N-bridgehead bicyclic urethane, polymerized in bulk under the influence of dibutyltin oxide and p-toluenesulfonic acid. In solution the monomer polymerizes in the presence of phosphoric acid. This is only the second example of ring opening polymerization of a bicyclo[3.3.1]nonane. The driving force in the present case is thought to be the relief of strain energy in the monomer conferred by its chair-boat conformation.     

Amphiphilic macromolecular nanostructure materials derived from 5-(octanoate methyl)bicyclo[2.2.1]hept-2-ene and 5-(phthalimide methyl)bicyclo[2.2.1]hept-2-ene via ring-opening metathesis copolymerization

Novel highly stable polynorbornenes with self-assembling amphiphilic architecture containing hydrophilic ammonium salt and hydrophobic alkyl ester group were obtained via ring-opening metathesis polymerization (ROMP) of 5-(octanoate methyl)bicyclo[2.2.1]hept-2-ene (NBMO) and 5-(phthalimide methyl)bicyclo[2.2.1]hept-2-ene (NBMPI), hydrogenation, hydrazinolysis, and subsequent quaternization. Polymeric micelles of such amphiphilic random and block polynorbornenes formed in solvents by varying the content of ammonium salts were investigated. Amphiphilic block copolymers exhibited perfect spherical morphology. Nanoscale polymeric micelles of random copolymers with 50-75 mol% of ammonium salts were roughly spherical in shape, while the morphologies of micelles transferred into network-like aggregates as hydrophilic contents of the random copolymers are higher than 80 mol%. The formation and fine structures of micelles were investigated by dynamic light scattering (DLS), TEM, and fluorescence technique using pyrene as fluorescence probe.     

N-Boc-6-氨基-3-苄基-3-氮杂双环[3.2.1]辛烷的合成

以降冰片烯-2-酰胺为原料,经霍夫曼降解、氨基保护、双键臭氧化、苄胺的还原氨化等反应合成N-Boc-6-氨基-3-苄基-3-氮杂双环[3.2.1]辛烷,通过对关键步骤的优化,总收率达到55.3％.该方法简单,操作容易且收率较高.