Polymers with electron-deficient olefin moieties by oxidation of precursors containing “push–pull” olefin (β-alkylmercaptoenoate) moieties in the main chain

Oxidation of a polymer (1) having β-alkylmercaptoenoate moieties in the main chain by m-chloroperbenzoic acid (MCPBA) is described. Oxidation of 1 proceeded selectively to give polymers having vinyl sulfoxide or vinyl sulfone moieties in the main chain by using an appropriate amount of MCPBA. In the case of 1.1 equiv of MCPBA (relative to the sulfur atom), a polymer (4) having vinyl sulfoxide moieties selectively in the main chain was obtained in quantitative yield without side reactions. Likewise, a polymer (5) having vinyl sulfone moieties was obtained in quantitative yield by using 2.6 equiv of MCPBA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2589–2592, 1998     

A materials approach to site-isolation of Grubbs catalysts from incompatible solvents and m-chloroperoxybenzoic acid

The development of a method for site-isolation of Grubbs second-generation catalyst from MCPBA is described. In these reactions, Grubbs catalyst was dissolved in a solvent consisting of a mixture (1:1 v/v) of 1-butyl-3-methylimidazolium hexafluorophosphate and methylene chloride and completely encapsulated within a thimble fabricated from polydimethylsiloxane (PDMS). A series of molecules that react by cross metathesis or ring-closing metathesis were added to the interior of the thimble and allowed to react. In the last step, m-chloroperoxybenzoic acid (MCPBA) dissolved in MeOH/H(2)O (1:1 v/v) was added to the exterior of the PDMS thimble. Small organic molecules diffused through the PDMS to react with MCPBA to form epoxides, but the Grubbs catalyst remained encapsulated. This result is important because Grubbs catalyst catalytically decomposes MCPBA at ratios of MCPBA to Grubbs of 3000 to 1. The yields for this two-step cascade sequence ranged from 67 to 83 %. The concept behind this sequence is that small organic molecules have high flux through PDMS but large molecules--such as Grubbs catalyst--and ionic reagents--such as MCPBA--have much lower flux through PDMS. Small molecules can thus react both outside and inside PDMS thimbles, whereas incompatible catalysts and reagents remain site-isolated from each other. This method does not require alteration of structures of the catalysts or reagents, so it may be applied to a wide range of homogeneous catalysts and reagents. To demonstrate further that the catalyst was encapsulated, the Grubbs catalyst was successfully recycled within the cascade sequence.     

Iodobenzene‐Catalyzed Synthesis of α‐Azidoketones and α‐Thiocyanatoketones from Aryl Ketones with MCPBA as a Cooxidant

Iodobenzene‐catalyzed synthesis of α‐azidoketones and α‐thiocyanatoketones from aryl ketones with MCPBA as a cooxidant is described. The method is simple, rapid and practical, generating α‐azidoketones and α‐thiocyanatoketones from the aryl ketone without isolation of α‐tosyloxyketones in good to excellent yields.     

Pheromone synthesis. Part 263: Synthesis of the racemate and the enantiomers of (E)-cis-6,7-epoxy-2-nonenal,the male-produced pheromone of the red-necked longhorn beetle,Aromia bungii

The racemate and the enantiomers of (E)-cis-6,7-epoxy-2-nonenal, the male pheromone of Aromia bungii, were synthesized by olefin cross metathesis between crotonaldehyde and (±)-, (+)- and (?)-cis-3,4-epoxy-7-octene. The epoxide was prepared by the Grignard coupling between allylmagnesium bromide and (±)-, (+)- and (?)-cis-2,3-epoxypentyl triflate. (±)-cis-2,3-Epoxy-1-pentanol was prepared by MCPBA epoxidation of (Z)-2-penten-1-ol, while its enantiomers were synthesized by the Sharpless asymmetric epoxidation of the allylic alcohol.     

Co-oligomerization of ethylene and higher linear alpha olefins. II. Olefin reactivities in various reaction steps of co-oligomerization with nickel ylide-based system

Part I described co-oligomerization reactions of ethylene and various linear α-olefins (propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, and 1-decene) in the presence of the homogeneous catalyst consisting of sulfonated nickel ylide and diethylaluminum ethoxide. The present article analyzes olefin reactivities in various reaction steps of the co-oligomerization reactions as well as reactivities of various catalytic species. Chain propagation reactions (insertion into the Ni? C bonds) with participation of α-olefins exhibit poor regioselectivity, primary insertion being ca. 60% more probable than the secondary insertion. Ethylene is significantly more reactive in chain propagation reactions: 50–70 times compared to olefin primary insertion and 100–120 times compared to olefin secondary insertion. Reactivities of α-olefins in chain propagation reactions decrease slightly for higher olefin alkyl groups. Reactivities of Ni? C bonds in chain propagation and chain termination reactions strongly depend on the structure of the alkyl group attached to the nickel atom. The Ni? CHR? CH₂? R bond has very low reactivity in ethylene insertion reaction and usually decomposes in the α-hydrogen elimination process. Kinetic analysis of olefin co-oligomerization reactions provides numerous analogies with olefin copolymerization reactions in the presence of Ziegler–Natta catalysts.     

Effect of kosmotrope and chaotrope anions on rate and equilibria processes for the α-cyclodextrin catalysed reaction of 3-chloroperbenzoic acid with iodide

Solutes, ranging from small hydrophobic molecules to macromolecular structures such as proteins, are heavily influenced by the presence of salts, particularly the anionic component. It is well known that anions possessing a high charge density, such as sulfate, are able to reduce the solubility of these solutes, with this effect likely to be entropically driven and based on the influence the anions have on the structure of water. Other anions with a lower charge density, such as perchlorate, can have the opposite effect, improving solubility. The current consensus for the latter effect is that rather than being as a result of changes to water structure, it is due to specific binding of the anions to solute molecules, acting to reduce unfavourable interactions with the solvent. In this paper we report on how both sulfate and perchlorate influence binding and catalysis for the α-cyclodextrin mediated reaction of iodide with 3-chloroperbenzoic acid (MCPBA) for which the cyclodextrin–MCPBA complex is the catalytic species. Kinetic runs have been carried out over the temperature range 15–35 °C in dilute nitric acid and with added sulfate and perchlorate, allowing the calculation of enthalpies and entropies for the rate and equilibria processes involved in this system. We show that both sulfate and perchlorate demonstrate the expected Hofmeister behaviours, with sulfate acting to exclude the MCPBA from solution into the cyclodextrin cavity, thus increasing the amount of the catalytic species, whereas perchlorate acts to solubilise the MCPBA. Perchlorate has a complex range of effects, since as well as forming an association complex with cyclodextrin, the thermodynamic parameters indicate that it may also associate with MCPBA and the MCPBA–cyclodextrin complex. These associations may explain the catalysis that is observed with increasing perchlorate concentration. The effects observed in this study may be relevant to other binding processes in chemistry and biology.     

New cascade processes on group 6 Fischer-type carbene complexes: cyclopropanation and metathesis reactions

Alkynyl Fischer carbene complexes 1, which feature a pendant olefin group, undergo novel cascade processes triggered by [2+2], [3+2], and [4+2] cycloadditions. Competition between cyclopropanation and olefin metathesis is controlled by the substitution at the double bond. The method described can be used to obtain different kind of polycarbo- and -heterocycles. A mechanistic explanation by means of DFT computational modeling is provided.     

Telluroxide elimination by direct oxidation of alkyl phenyl telluride

Treatment of sec-alkyl phenyl tellurides, except for the cyclohexyl system, with m-chloroperbenzoic acid(MCPBA) in diethyl ether readily afforded the corresponding olefins in good yields presumably via telluroxide elimination together with small amounts of alcohols and ketones. In the pri-alkyl and cyclohexyl cases the adducts between MCPBA and the tellurides were isolated as stable organotellurium(IV) compounds which gave similar elimination products by neat pyrolysis at 220–2500°C.     

Synthesis of natural ecteinascidins (ET-729, ET-745, ET-759B, ET-736, ET-637, ET-594) from cyanosafracin B

The semisynthetic process initially described for the synthesis of 1 (ET-743) has been extended to the preparation of other natural ecteinascidins. For the synthesis of 2 (ET-729) a demethylation of a N-Me intermediate was carried out by a selective oxidation with MCPBA. Other natural ecteinascidins (ET-745, ET-759B, ET-736, ET-637, ET-594) were accessible from key intermediate 25. The described methodologies allow for the preparation of a wide variety of ecteinascidins by procedures that can be easily scaled up.     

Selective preparation of glycosyl sulfone or glycal by treatment of phenyl thioglycoside of N-acetylneuraminic acid with m-chloroperbenzoic acid

Treatment of acetylated phenyl thioglycoside of N-acetylneuraminic acid with m-chloroperbenzoic acid (MCPBA) in CH₂Cl₂ affords quantitatively mixtures of the respective sulfone and glycal free from the sulfoxide. The outcome of the reaction does not depend on the anomeric configuration of the starting thioglycoside. The sulfone can be selectively prepared (yield 100%) by oxidation with an excess of MCPBA and NaHCO₃. In the presence of pyridine (2 equiv.) and MCPBA (2 equiv.), the major product is glycal (yields 81—88%). This version of the reaction can be regarded as a new method for the preparation of sialic acid glycals.     

Synthesis of oxazirino[2,3‐a][1,5]benzodiazepines by oxidation of 1H‐1,5‐benzodiazepines with m‐chloroperbenzoic acid (MCPBA)

2,4‐Disubstituted 1‐benzoyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepines were oxidized by m‐chloroperbenzoic acid (MCPBA) to produce 1a,3‐disubstituted 4‐benzoyl‐1a,2,3,4‐tetrahydro‐oxazirino[2,3‐a][1,5]benzodiazepines, a novel tricyclic heterocyclic system. However, 2,4‐disubstituted 2,3‐dihydro‐1H‐1,5‐benzodiazepines were oxidized by MCPBA under the same conditions to give a 2,4‐disubstituted 2,3‐dihydro‐2‐hydroxy‐1H‐1,5‐benzodiazepine or a 2,4‐disubstituted 3H‐1,5‐benzodiazepine, respectively. We propose a hydroxylation mechanism of peracid oxidation. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:158–162, 2000     

Structural investigation of high-valent manganese-salen complexes by UV/Vis,Raman, XANES,and EXAFS spectroscopy

XANES and EXAFS spectroscopic studies at the Mn-K- and Br-K-edge of reaction products of (S,S)-(+)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III) chloride ([(salen)Mn(III)Cl], 1) and (S,S)-(+)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III) bromide ([(salen)Mn(III)Br], 2) with 4-phenylpyridine N-oxide (4-PPNO) and 3-chloroperoxybenzoic acid (MCPBA) are reported. The reaction of the Mn(III) complexes with two equivalents of 4-PPNO leads to a hexacoordinated compound, in which the manganese atom is octahedrally coordinated by four oxygen/nitrogen atoms of the salen ligand at an average distance of approximately 1.90 A and two additional, axially bonded oxygen atoms of the 4-PPNO at 2.25 A. The oxidation state of this complex was determined as approximately +IV by a comparative study of Mn(III) and Mn(V) reference compounds. The green intermediate obtained in reactions of MCPBA and solutions of 1 or 2 in acetonitrile was investigated with XANES, EXAFS, UV/Vis, and Raman spectroscopy, and an increase of the coordination number of the manganese atoms from 4 to 5 and the complete abstraction of the halide was observed. A formal oxidation state of IV was deduced from the relative position of the pre-edge 1s-->3d feature of the X-ray absorption spectrum of the complex. The broad UV/Vis band of this complex in acetonitrile with lambda(max)=648 nm was consistent with a radical cation structure, in which a MCPBA molecule was bound to the Mn(IV) central atom. An oxomanganese(V) or a dimeric manganese(IV) species was not detected.     

The vinylogous intramolecular Morita-Baylis-Hillman reaction: synthesis of functionalized cyclopentenes and cyclohexenes with trialkylphosphines as nucleophilic catalysts

The development of the vinylogous intramolecular Morita-Baylis-Hillman reaction for the synthesis of functionalized cyclopentenes and cyclohexenes is described. The reaction involves the trialkyphosphine-catalyzed cyclization of 1,6- or 1,7-diactivated 1,5-hexadienes or 1,6-heptadienes, containing carboxyaldehyde, methyl ketone, or methoxycarbonyl as the olefin activating groups. A representative example of this reaction is the Me(3)P-catalyzed cyclization of 1a in tert-amyl alcohol, which provides the substituted cyclopentene 2a in 95% yield and with 97:3 regioselectivity.     

Solid phase synthesis of an extensively focused library of thiadiazole ethers

An approach to combine the advantages of random and of focused combinatorial libraries in pharmaceutical research is described with the example of a solid phase synthesis of 2,5-disubstituted thiadiazole ethers. Key steps of synthesis are the introduction of the heterocycle by selective, sequential nucleophilic double substitution of 2,5-bis(methylsulfonyl)-1,3,4-thiadiazole and the oxidation of the benzylsulfanyl-1,3,4-thiadiazole to the corresponding sulfone using MCPBA on solid phase.     

Gold(I)-catalyzed ring expansion of cyclopropanols and cyclobutanols

The rearrangement of 1-alkynyl cyclobutanols and cyclopropanols to alkylidene cycloalkanones catalyzed by cationic triarylphosphine gold(I) complexes is described. The reaction tolerates terminal alkynes as well as alkyl, aryl, and halo-substitution at the acetylenic position and stereoselectively provides a single olefin isomer. The gold(I)-catalyzed rearrangement is stereospecific with regard to substituents on the ring, thus providing a practical method for the stereoselective synthesis of highly substituted cyclopentanones from cyclopropanols. The reaction stereoselectively provides a single olefin isomer and is stereospecific with regard to substituents on the ring via sequential gold(I)-catalyzed ring expansion reactions.     

Stereoselective Epoxidation of Cyclohexa-Anellated Triquinacenes with Iodine/Silver(I) Oxide As Compared to m-Chloroperbenzoic Acid(1)

Iodine/silver(I) oxide (I(2)/Ag(2)O) reacts highly stereoselectively in the single, double, and triple anti epoxidation of the spherical 1,4,7-triene, 10-methyl-2,3:5,6:8,9-tris(cyclohexano)triquinacene 1. All of the three epoxides 3, 4, and 5 obtained with this reagent contain the epoxy groups at the convex side of the triquinacene framework. The stereochemical course of the epoxidation with I(2)/Ag(2)O is clearly distinct from that observed with m-chloroperbenzoic acid (MCPBA), which gives the same monoepoxide (3) but exclusively anti,syn di- and triepoxides (6-8) bearing at least one epoxy group at the concave side of the triquinacene framework. Epoxidation of the related three-fold 1,4-cyclohexadiene, tris(cyclohexeno)triquinacene 2, with MCPBA occurs similarly to the conversion of 1, whereas I(2)/Ag(2)O reacts with high regioselectivity at the less electron-rich peripheral double bonds of 2 giving triepoxides 12 and 13. The molecular structure of triepoxide 8 has been elucidated in detail by X-ray crystal structure analysis.     

Reactions of peroxide radicals with the surface of heterogeneous catalysts in homolytic and heterolytic processes

An interrelation between homolytic and heterolytic stages is found for olefin epoxidation by hydroperoxides and cumene hydroperoxide decomposition in the presence of a heterogeneous catalyst (molybdenum selenide). Peroxide radicals that are formed in homolytic decomposition of the hydroperoxide interact with the catalyst surface. As a result, molybdenum atoms are oxidized to the highest valence state, and new reaction sites are created, on which heterolytic reactions occur. It is shown that olefin, as an electron donor, decreases the catalyst activity in the heterolytic reactions. The limited value for the olefin epoxidation rate, which is independent of the amount of the catalyst used, is explained by the disappearance of active sites on the catalyst surface due to their interaction with the neighboring sites containing adsorbed olefin molecules.     

Retrospect of Se and Te Chemistry

Retrospect of organoselenium and tellurium chemistry for these 30 years is described focusing on our novel findings in this field: (1) telluroxide elimination leading to alkenes and allylic compounds, (2) Pd-catalyzed or –mediated carbodetelluration for a new C–C bond formation, (3) synthesis of chiral diferrocenyl dichalcogenides and their use as chiral auxiliaries, (4) asymmetric selenoxide elimination for making optically active allenes and alkenes, (5) meta chloroperbenzoic acid (MCPBA) oxidation of organic selenides and tellurides leading to a substitution of a PhSe or PhTe moiety, as well as (6) preparation of chalcogen-bridged diruthenium complexes and their catalytic use for propargylic substitution reactions.     

Robust and efficient molecular catalysts with a M-O-M' framework

Heterodimetallic systems are the most interesting among the heteropolynuclear compounds. The importance of these molecules is mainly due to their catalytic properties. Although various types of heterodimetallic systems are known the framework with a M-O-M' arrangement is of particular importance. This stems from its ability to catalyze various transformations. The improved catalytic ability is due to the oxygen bridge that makes the metal centres more electrophilic which is an essential criteria for a system to function as a catalyst. Therefore, the present article focuses on the synthesis of the M-O-M' system and explores the application of such materials as catalysts in olefin polymerization, ring opening polymerization of caprolactone, olefin epoxidation, and olefin hydroformylation reactions.     

HRP-12催化剂上苯与直链烯烃的烷基化反应 Ⅰ. 本征反应动力学研究

直链烷基苯是生产阴离子表面活性剂直链烷基苯磺酸盐的重要原料。2000年以美国环球油品公司(UOP)的脱氢法工艺生产的直链烷基苯占世界直链烷基苯产量的88％。脱氢法以液体氢氟酸为催化剂由正构烯烃与苯进行烷基化反应生产直链烷基苯。由于液体氢氟酸催化剂具有较强的腐蚀