Hypervalent phenyl-λ3-iodane-mediated para-selective aromatic fluorination of 3-phenylpropyl ethers

Exposure of 3-phenylpropyl ethers to an activated iodosylbenzene monomer·18-crown-6 complex [PhI(OH)BF(4)·18C6] in the presence of BF(3)-Et(2)O and water results in the para-selective monofluorination of benzene ring via neighboring alkoxy group participation and directly affords 3-(4-fluorophenyl)propyl ethers regioselectively in good yields.     

Isolation, characterization, and reaction of activated iodosylbenzene monomer hydroxy(phenyl)iodonium ion with hypervalent bonding: supramolecular complex PhI+OH.18-crown-6 with secondary I...O interactions

The isolation, characterization, and reaction of the active species hydroxy(phenyl)iodonium ion with hypervalent bonding are reported. Reaction of iodosylbenzene with HBF(4)-Me(2)O in the presence of equimolar 18-crown-6 in dichloromethane afforded the hydroxy-lambda(3)-iodane complex PhI(OH)BF(4).18-crown-6 as stable yellow prisms. X-ray structure analysis indicated that both the close contacts between the iodine(III) and the three adjacent oxygen atoms of 18-crown-6, and the hydrogen bonding OH.O(crown ether) will be responsible for the increased stability of the complex as compared to the uncomplexed PhI(OH)BF(4). The crown ether complex is highly reactive and serves as a versatile oxidant even in water: thus, the complex undergoes oxidative transformations of a variety of functional groups such as olefins, alkynes, enones, silyl enol ethers, sulfides, and phenols under mild conditions.     

One-pot regioselective synthesis of chromanyl(phenyl)-lambda(3)-iodanes: tandem oxidative cyclization and lambda(3)-iodanation of 3-phenylpropanols

Reaction of 3-phenylpropanol with an activated iodosylbenzene-18-crown-6 complex [PhI(OH)BF4-18C6] in dichloromethane in the presence of BF3-Et2O afforded directly the 6-chromanyl(phenyl)-lambda3-iodane-18C6 complex through tandem oxidative intramolecular cyclization yielding chroman and its regioselective phenyl-lambda3-iodanation.     

Iodobenzene-catalyzed alpha-acetoxylation of ketones. in situ generation of hypervalent (diacyloxyiodo)benzenes using m-chloroperbenzoic acid

Reported here for the first time is the iodobenzene-catalyzed alpha-oxidation of ketones, in which diacyloxy(phenyl)-lambda3-iodanes generated in situ act as real oxidants of ketones and m-chloroperbenzoic acid serves as a terminal oxidant. Oxidation of a ketone with m-chloroperbenzoic acid in acetic acid in the presence of a catalytic amount of iodobenzene, BF3.Et2O, and water at room temperature under argon affords an alpha-acetoxy ketone in good yield. p-Methyl- and p-chloroiodobenzene also serve as efficient catalysts in this direct oxidation. We found that when the reaction was carried out in the absence of a catalytic amount of iodobenzene, Baeyer-Villiger oxidation of a ketone took place. It is noted that use of water and BF3.Et2O is crucial to the success of this alpha-acetoxylation.     

Oxidative Cyclization of Iodo Ketones. Synthesis of 6-Oxa-5alpha-pregnane-3,20-dione

The steroidal delta- and gamma-iodo ketones 1 and 9 were converted to the cyclic hemiketals 3 and 10, by oxidation to the iodoso derivatives with m-CPBA. Spontaneous cyclization of the latter intermediates to the corresponding oxocarbenium ions, followed by stereoselective addition of water, rendered the hemiketals. Depending on the reaction conditions, the five-membered oxocarbenium ion derived from the gamma-iodo ketone 9 may add H(2)O or m-CPBA to give either the hemiketal or a Baeyer-Villiger type product 12, while the oxocarbenium derived from 1 gives exclusively the hemiketal. When the reaction was carried out in dry methanol, methyl ketals were formed. Use of this methodology allowed us to synthesize 6-oxa-5alpha-pregnanes with and without functionalization at C-19.     

Hofmann-type rearrangement of imides by in situ generation of imide-hypervalent iodines(III) from iodoarenes

The Hofmann-type rearrangement of aromatic and aliphatic imides using a hypervalent iodine(III) reagent generated in situ from PhI, m-CPBA, and TsOH·H(2)O proceeded in the presence of a base in alcohol to provide anthranilic acid derivatives and amino acid derivatives in high yields, respectively. This reaction proceeds through a tandem reaction via alcoholysis followed by a Hofmann rearrangement promoted by the formation of an imide-λ(3)-iodane intermediate.     

Synthetic application of water-soluble hypervalent iodine reagents in aqueous media

Along with the vigorous development of hypervalent iodine chemistry, water-soluble hypervalent iodine reagents have received considerable attentions in recent years. In order to obtain water-soluble hypervalent iodine reagents, two strategies have been employed including introduction of hydrophilic functional groups onto the phenyl ring and formation of complex of iodosylbenzene with crown ether. And, it is observed that four kinds of hypervalent iodine reagents exhibit more or less solubility in water including hypervalent iodine reagents containing hydrophilic ligands, diaryliodonium salts, oligomeric iodosylbenzene sulfate, and iodylbenzene and its derivatives. In this review, we summarize these water-soluble hypervalent iodine reagents and their broad synthetic applications in aqueous media.     

细胞色素P-450模拟体系的活性中间体-氧配位铬(V)四苯基卟啉 配合物的分离、 表征和氧化反应

氮气保护下二氯甲烷中铬(III)四苯基卟啉衍生物在-40℃与亚碘酰苯反应,分离得氧配位铬(V)四苯基卟啉配合物:O=Cr(V)TPP(Cl)PhI,O=Cr(V)TPP(N~30PhI,O=Cr(V)TPP(p-CH~3O-C~6H~4O)(1/2)PhI。已经元素分析、可见、红外、顺磁、核磁和质谱法结构表征。这些配合物能氧化苯乙烯,环己醇,环己烯和环己烷,可作为细胞色素P-450模拟体系的活性中间体。     

BF3.2CF3CH2OH (BF3.2TFE), an efficient superacidic catalyst for some organic synthetic transformations

BF3.2CF3CH2OH complex was found to be a very effective superacidic catalyst comparable in acid strength to at least that of 100% anhydrous sulfuric acid for various acid-catalyzed organic transformations such as isomerizations, rearrangements, ionic hydrogenation of various ketones, and aromatics with triethylsilane and nitration of aromatics with metal nitrate. Studies of the pivalaldehyde-methyl isopropyl ketone rearrangement and the benzopinacol to phenanthrene transformation suggest that the complex has an acidity comparable to that of 100% anhydrous sulfuric acid. The structure and properties of the 1:2 boron trifluoride-trifluoroethanol complex have been further studied using NMR (1H, 13C, 19F, 11B) and DFT calculations at the B3LYP/6-311++G//B3LYP/6-31G level.     

Synthesis of novel cage oxaheterocycles

m-CPBA-promoted Baeyer-Villiger oxidation of pentacyclo[6.3.0.0(2,6).0(3,10).0(5,9)]undecan-4-one (1) afforded the corresponding lactone 2 in 93% yield. Lithium aluminum hydride promoted reduction of lactones 2, 6, and 9, performed in the presence of BF(3).OEt(2) reagent, afforded the corresponding cage ethers, i.e., 4, 7, and 10, respectively. Two methods that can be used to replace a cage C=O group by ether oxygen without concomitant rearrangement are delineated. A key step in the first of these methods employs m-CPBA promoted "double Criegee rearrangement", which was used to convert pentacyclo[6.3.0.0(2,6).0(3,10).0(5,9)]undecan-4-one diethyl acetal (11) into 7,9-dioxapentacyclo-[8.3.0.0(2,6).0(3,12).0(5,11)]tridecan-8-one (12). Subsequently, 12 was converted into 4-oxapentacyclo[6.3.0.0(2,6).0(3,10).0(5,9)]undecane (14) via a two-step reduction-dehydration reaction sequence. The second method utilized PhI(OAc)(2)-I(2) reagent to convert cage lactols 15 and 17 into the corresponding cage ethers, i.e., 14 and 2-oxaadamantane (18), respectively.     

4‐Ethoxycarbonyl‐3‐hydroxy‐3‐phenylcyclohexanone

The title compound, ethyl 2‐hydroxy‐4‐oxo‐2‐phenyl­cyclo­hexane­carboxyl­ate, C₁₅H₁₈O₄, was obtained by a Michael–Aldol condensation and has the cyclo­hexanone in a chair conformation. The attached hydroxy, ethoxy­carbonyl and phenyl groups are disposed in β‐axial, β‐equatorial and α‐­equatorial configurations, respectively. An intermolecular hydrogen bond, with an O?O distance of 2.874 (2) Å, links the OH group and the ring carbonyl. Weak intermolecular C—H?O=C (ester and ketone), O—H?O=C (ketone) and C—H?OH hydrogen bonds exist.     

细胞色素P-450模拟体系的活性中间体—亚碘酰苯铬(Ⅳ)四苯基卟啉配合物的分离、表征和氧化反应

铬(Ⅲ)四苯基卟啉-亚碘酰苯体系在温和条件下能催化氧化碳氢化合物,是细胞色素P-450很好的模拟体系。分离和表征细胞色素P-450模拟体系的活性中间体,不仅能解释细胞色素P-450模拟体系催化氧化碳氢化合物的反应机理,而且也有助于深入了解细胞色素P-450催化氧化碳氢化合物的反应机理及其活性中间体的结构。我们首先分离和表征的细胞色素P-450模拟体系的一种活性中间体-氧配位铬(V)四苯基卟啉配合物,具有氧化碳氢化合物的活性。这篇论文报道细胞色素P-450模拟体系的另一种活性中间体-亚碘酰苯铬(Ⅳ)四苯基卟啉配合物的分离,表征和对环已烯的氧化性质。     

新型非对称二苯并[b,f][1,5]二氮杂环辛四烯的合成

以两种不同取代的2-氨基二苯甲酮为原料,氯苯为溶剂,BF3-Et2O为脱水剂,通过分子间脱水一步环化缩合制备非对称二苯并[b,f][1,5]二氮杂环辛四烯衍生物。运用HPLC监控反应过程,优化合成工艺,得到最佳反应条件为:等物质的量的两种不同取代2-氨基二苯甲酮和BF3-Et2O,在氯苯中回流反应12 h。化合物4a^4c为新化合物,其结构经1H NMR,13C NMR和MS(ESI)表征。     

三甲硅基醚的断裂研究

Sommer等[1]首次应用（Me3SiO）2SO2向醇羟基引人三甲硅基（TMS）以保护羟基以来，已发展出很多方便有效的向醇羟基引人TMS保护基团的方法[2]．通常，立体阻碍越小的醇，其羟基越容易被硅基化，而且该TMS保护基团也就越容易在酸或碱性条件下被水解脱除[2]我们在天然产物PrehisPanolone的合成中[3]，羟基r-丁烯酸内酯2是一个关键的中间体．如何脱除前体三甲硅基醚的r-丁烯酸内酯1中的TMS保护基团是一个关键的问题．我们采用四了基氟化铵（TBAF）[4]（A）、酸性水解[5]（B）、碱性醇解[6]（C）和三氟化硼乙醚溶液（BF3-Et2O）[7]…     

The reactive chemisorption of alkyl iodides at Cu(110) and Ag(111) surfaces: a combined STM and XPS study

The chemisorption of methyl and phenyl iodide has been studied at Cu(110) and Ag(111) surfaces at 290 K with STM and XPS. At both surfaces dissociative adsorption of both molecules leads to chemisorbed iodine, with the STM showing c(2 x 2) and (square root 3 x square root 3)R30 structures at the Cu(110) and Ag(111) surfaces, respectively. At the Cu(110) surface a comparison of coexisting c(2 x 2) I(a) and p(2 x 1) O(a) domains shows the iodine adatoms to be chemisorbed in hollow sites with evidence at low coverage for diffusion in the (110) direction. In the case of methyl iodide no carbon adsorption is observed at either the silver or the copper surfaces, but chemisorbed phenyl groups are imaged at the Cu(110) surface after exposure to phenyl iodide. The STM images show the phenyl groups as bright features approximately 0.7 nm in diameter and 0.11 nm above the iodine adlayer, reaching a maximum surface concentration after approximately 6 Langmuir exposure. However, the phenyl coverage decreases with subsequent exposures to PhI and is negligible by approximately 1000 L exposure, consistent with the formation and desorption of biphenyl. The adsorbed phenyls are located above hollow sites in the substrate, they are stabilized at the top and bottom of step edges and in paired chains (1.1 nm apart) on the terraces with a regular interphenyl spacing within the chains of 1.0 nm in the (110) direction. The interphenyl ring spacing and diffusion of individual phenyls from within the chains shows that the chains do not consist of biphenyl species but may be a precursor to their formation. Although the XPS data shows carbon present at the Ag(111) surface after exposure to PhI, no features attributable to phenyl groups were observed by STM.     

五氟代锰卟啉模拟酶体系快速混合停流吸收谱

采用快速混合停流技术,在实际反应条件下,考察了五氟代锰卟啉配合物Ｍｎ~Ⅲ（ＴＦＰＰ）Ｃ１与两种单氧给体亚碘酰苯ＰｈＩＯ和过氧苯甲酸ｍ－ＣＰＢＡ构建的细胞色素Ｐ－４５０模拟酶体系催化活性物种的生成及催化烯烃环氧化过程．在氧给体ＰｈＩＯ作用下,Ｍｎ~Ⅲ（ＴＦＰＰ）Ｃ１生成了高价锰氧卟啉配合物和双核μ－氧锰卟啉配合物,具有高的催化环氧化活性和催化剂稳定性．而在氧给体ｍ－ＣＰＢＡ作用下,Ｍｎ~Ⅲ（ＴＦＰＰ）Ｃ１则生成了一种较稳定物种,以致催化活性较低。     

High-intensity ultrasound-promoted reformatsky reactions

Reformatsky reactions of a phenyl ketone, an alpha-bromoester, zinc dust, and a catalytic amount of iodine in dioxane under high-intensity ultrasound (HIU) irradiation from an ultrasonic probe give high yields of beta-hydroxyesters in short reaction times. A series of alkyl phenyl ketones with increasing steric demands of the alkyl group are evaluated as potential electrophiles for the reactions with several alpha-bromoesters, also having increasing steric demands. The Reformatsky reaction under HIU is found to be concentration dependent.     

Synthesis, structure, and luminescent properties of microporous lanthanide metal-organic frameworks with inorganic rod-shaped building units

A series of microporous lanthanide metal-organic frameworks, Tb3(BDC)(4.5)(DMF)2(H2O)3.(DMF)(H2O) (1) and Ln3(BDC)(4.5)(DMF)2(H2O)3.(DMF)(C2H5OH)(0.5)(H2O)(0.5) [Ln = Dy (2), Ho (3), Er (4)], have been synthesized by the reaction of the lanthanide metal ion (Ln3+) with 1,4-benzenedicarboxylic acid and triethylenetetramine in a mixed solution of N,N'-dimethylformamide (DMF), water, and C(2)H(5)OH. X-ray diffraction analyses reveal that they are extremely similar in structure and crystallized in triclinic space group P. An edge-sharing metallic dimer and 4 metallic monomers assemble with 18 carboxylate groups to form discrete inorganic rod-shaped building units [Ln6(CO2)18], which link to each other through phenyl groups to lead to three-dimensional open frameworks with approximately 4 x 6 A rhombic channels along the [0,-1,1] direction. A water sorption isotherm proves that guest molecules in the framework of complex 1 can be removed to create permanent microporosity and about four water molecules per formula unit can be adsorbed into the micropores. These complexes exhibit blue fluorescence, and complex 1 shows a Tb3+ characteristic emission in the range of 450-650 nm.     

Novel Pd/C-catalyzed redox reactions between aliphatic secondary alcohols and ketones under hydrogenation conditions: application to H-D exchange reaction and the mechanistic study

A liquid-phase redox system between secondary alcohols and ketones is described. Deuteration of either secondary alcohols or ketones using the Pd/C-H2-D2O system gave a mixture of deuterium-labeled secondary alcohols and ketones. The results indicated that the secondary alcohol was oxidized to the corresponding ketone without oxidants under the hydrogenation conditions and the hydrogenation of the aliphatic ketone to the corresponding secondary alcohol simultaneously proceeded. Detailed mechanistic studies on the redox system as well as the H-D exchange reaction are discussed.     

Hypervalent iodine-mediated ring contraction reactions

Hypervalent iodine reagents constitute a powerful tool in modern synthetic organic chemistry, promoting several important reactions. One such reaction is the ring contraction of cycloalkenes and cycloalkanones promoted by iodine(III) compounds, such as iodobenzene diacetate, iodosylbenzene, iodotoluene difluoride, and [hydroxy(tosyloxy)- iodo]benzene (Koser' s reagent). This review covers all the literature related to the ring contraction of cyclic ketones and olefins promoted by iodine(III) species.