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1.
Primary alcohols from terminal olefins: formal anti-Markovnikov hydration via triple relay catalysis
Alcohol synthesis is critical to the chemical and pharmaceutical industries. The addition of water across olefins to form primary alcohols (anti-Markovnikov olefin hydration) would be a broadly useful reaction but has largely proven elusive; an indirect hydroboration/oxidation sequence requiring stoichiometric borane and oxidant is currently the most practical methodology. Here, we report a more direct approach with the use of a triple relay catalysis system that couples palladium-catalyzed oxidation, acid-catalyzed hydrolysis, and ruthenium-catalyzed reduction cycles. Aryl-substituted terminal olefins are converted to primary alcohols by net reaction with water in good yield and excellent regioselectivity. 相似文献
2.
Formation of catalytic metal-molecule contacts 总被引：1，自引：0，他引：1
Tulevski GS Myers MB Hybertsen MS Steigerwald ML Nuckolls C 《Science (New York, N.Y.)》2005,309(5734):591-594
We describe a new strategy for the in situ growth of molecular wires predicated on the synthesis of a trifunctional "primed" contact formed from metal-carbon multiple bonds. The ruthenium-carbon pi bond provides structural stability to the molecular linkages under ambient conditions, and density functional calculations indicate the formation of an efficient conduit for charge carriers to pass between the metal and the molecule. Moreover, the metal-carbon pi bond provides a chemically reactive site from which a conjugated molecular wire can be grown in situ through an olefin metathesis reaction. 相似文献
3.
The insertion of an iridium complex into an N-H bond in ammonia leads to a stable monomeric amido hydride complex in solution at room temperature. This reaction advances the transition-metal coordination chemistry of ammonia beyond its role for more than a century as an ancillary ligand. The precursor for this insertion reaction is an iridium(I) olefin complex with an aliphatic ligand containing one carbon and two phosphorus donor atoms. Kinetic and isotopic labeling studies indicate that olefin dissociates to give a 14-electron iridium(I) fragment, which then reacts with ammonia. This cleavage of the N-H bond under neutral conditions provides a foundation on which to develop future mild catalytic transformations of ammonia, such as olefin hydroamination and arene oxidative amination. 相似文献
4.
Diazomethane is a common and versatile reagent in organic synthesis whose broader use is generally impeded by its explosiveness and toxicity. Here we report that a simple iron porphyrin complex catalyzes the cyclopropanation of styrenes, enynes, and dienes under the demanding conditions [aqueous 6 molar potassium hydroxide (KOH) solution, open to air] necessary for the in situ generation of diazomethane from a water-soluble diazald derivative. A biphasic reaction medium arising from the immiscibility of the olefin substrates with water appears essential to the overall efficiency of the process. The work we describe highlights an approach to catalysis with untoward reactive intermediates, in which the conditions for their generation under operationally safe regimes dictate catalyst selection. 相似文献
5.
Given the widespread importance of amides in biochemical and chemical systems, an efficient synthesis that avoids wasteful use of stoichiometric coupling reagents or corrosive acidic and basic media is highly desirable. We report a reaction in which primary amines are directly acylated by equimolar amounts of alcohols to produce amides and molecular hydrogen (the only products) in high yields and high turnover numbers. This reaction is catalyzed by a ruthenium complex based on a dearomatized PNN-type ligand [where PNN is 2-(di-tert-butylphosphinomethyl)-6-(diethylaminomethyl)pyridine], and no base or acid promoters are required. Use of primary diamines in the reaction leads to bis-amides, whereas with a mixed primary-secondary amine substrate, chemoselective acylation of the primary amine group takes place. The proposed mechanism involves dehydrogenation of hemiaminal intermediates formed by the reaction of an aldehyde intermediate with the amine. 相似文献
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Polymer synthesis and organotransition metal chemistry 总被引：4，自引：0，他引：4
Mechanistic and synthetic studies in organometallic chemistry have provided considerable insight into olefin metathesis and Ziegler-Natta polymerization. New homogeneous olefin metathesis catalysts based on high oxidation state transition metals have opened new opportunities in polymer synthesis by providing unprecedented control in ring-opening polymerization of cyclic alkenes. The recent development of living coordinative polymerization systems has led to the preparation of a number of new, interesting materials, including block copolymers, conducting polymers or precursors, and ionophoric polymeric substrates. 相似文献
8.
The complex Ni[S2C2(CF3)2]2 reacts with light olefins, including ethylene and propylene, selectively and reversibly. The reaction is not poisoned by hydrogen gas, carbon monoxide, acetylene, or hydrogen sulfide, which are commonly present in olefin streams, presumably because olefin binding occurs through the sulfur ligand rather than the metal center. The reversible reaction of olefins with Ni[S2C2(CN)2]2n (n = 0, -1, -2) can be controlled electrochemically, where the oxidation state-dependent binding and release of olefins are fast on the electrochemical time scale. The observed tolerance to poisons and controllable electrochemical reactivity present an alternative approach to the separation of olefins from complex streams. 相似文献
9.
The formation of a single product from terminal functionalization of linear alkanes from a transition metal-catalyzed reaction is reported. The rhodium complex Cp*Rh(eta(4)-C(6)Me(6)) (Cp*, C(5)Me(5); Me, methyl) catalyzes the high-yield formation of linear alkylboranes from commercially available borane reagents under thermal conditions. These reactions now allow catalytic, regiospecific functionalization of alkanes under thermal conditions. The organoborane products are among the most versatile synthetic intermediates in chemistry and serve as convenient precursors to alcohols, amines, and other common classes of functionalized molecules. 相似文献
10.
Goldman AS Roy AH Huang Z Ahuja R Schinski W Brookhart M 《Science (New York, N.Y.)》2006,312(5771):257-261
With petroleum supplies dwindling, there is increasing interest in selective methods for transforming other carbon feedstocks into hydrocarbons suitable for transportation fuel. We report the development of highly productive, well-defined, tandem catalytic systems for the metathesis of n-alkanes. Each system comprises one molecular catalyst (a "pincer"-ligated iridium complex) that effects alkane dehydrogenation and olefin hydrogenation, plus a second catalyst (molecular or solid-phase) for olefin metathesis. The systems all show complete selectivity for linear (n-alkane) product. We report one example that achieves selectivity with respect to the distribution of product molecular weights, in which n-decane is the predominant high-molecular-weight product of the metathesis of two moles of n-hexane. 相似文献
11.
Serendipity has long been a welcome yet elusive phenomenon in the advancement of chemistry. We sought to exploit serendipity as a means of rapidly identifying unanticipated chemical transformations. By using a high-throughput, automated workflow and evaluating a large number of random reactions, we have discovered a photoredox-catalyzed C-H arylation reaction for the construction of benzylic amines, an important structural motif within pharmaceutical compounds that is not readily accessed via simple substrates. The mechanism directly couples tertiary amines with cyanoaromatics by using mild and operationally trivial conditions. 相似文献
12.
Fluorescamine: a reagent for assay of amino acids, peptides, proteins, and primary amines in the picomole range 总被引：174，自引：0，他引：174
S Udenfriend S Stein P B?hlen W Dairman W Leimgruber M Weigele 《Science (New York, N.Y.)》1972,178(63):871-872
Fluorescamine is a new reagent for the detection of primary amines in the picomole range. Its reaction with amines is almost instantaneous at room temperature in aqueous media. The products are highly fluorescent, whereas the reagent and its degradation products are nonfluorescent. Applications are discussed. 相似文献
13.
Products of unfavorable chemical equilibria are not readily observed because their high energy and increased reactivity result in low concentrations. Biological macromolecules use binding forces to access unfavorable equilibria and stabilize reactive intermediates by isolating them from the medium. In a similar vein, we describe here a synthetic receptor that allows direct observation of labile tetrahedral intermediates: hemiaminals formed in the reaction of an aldehyde carbonyl group with amines. The receptor encapsulates alkyl-substituted primary amines, then orients them toward a covalently tethered aldehyde function. The hemiaminal intermediates appear at high concentration, confined from the bulk solution and observable at ambient temperature by conventional nuclear magnetic resonance spectroscopy. 相似文献
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为了提高苎麻纤维的染色性能,分别采用乙二胺、二甲胺、三乙醇胺接枝改性苎麻纤维,并对改性工艺进行了研究.分析了接枝温度、浓度和时间对改性苎麻染色性能的影响,得到乙二胺、二甲胺及三乙醇胺接枝苎麻纤维的最佳工艺条件.结果表明:这些胺能够在较温和的条件下接枝改性苎麻纤维,胺化接枝苎麻纤维的上染率和固色率显著提高,可以实现活性染料无盐染色. 相似文献
16.
Direct catalytic hydration of terminal alkenes to primary alcohols would be an inexpensive route to industrially useful alcohols and a convenient synthetic route for the synthesis of terminal alcohols in general. The reaction between trans- PtHCl(PMe(3))(2) (where Me = CH(3)) and sodium hydroxide in a one-to-one mixture of water and 1-hexene yields a species that, at 60 degrees C and in the presence of the phasetransfer catalyst benzyltriethylammonium chloride, catalyzes selective hydration of 1-hexene to n-hexanol at a rate of 6.9 +/- 0.2 turnovers per hour. Hydration of 1-dodecene to n-dodecanol occurs at a rate of 8.3 +/- 0.4 turnovers per hour at 100 degrees C. Deuterium labeling experiments with trans-PtDCl(PMe(3))(2) show that hydration involves reductive elimination of a C-H bond. At low hydroxide concentrations (<8 equivalents), hydration of the water-soluble olefin 3-butene-1-ol to 1,4-butanediol exhibited a first-order dependence on hydroxide concentration for loss of catalytic activity. This suggests that hydroxide attacks the coordinated alkene slowly. At high hydroxide concentrations, the rate of catalysis was hydroxide-independent and first order in alkene. Substitution of coordinated water (k(1) = 9.3 +/- 0.5 x 10(-3) liters per mol per second) appears to be limitng under these conditions. 相似文献
17.
KEELER RF 《Science (New York, N.Y.)》1959,129(3363):1617-1618
Proteins, certain amino acids, and amines undergo a potentially useful color reaction. The reaction involves the apparent formation of pyrroles when the compounds are allowed to react with acetonylacetone. The pyrroles yield colored complexes on coupling with p-dimethylaminobenzaldehyde. This report describes the specificity and possible uses of this reaction in colorimetric measurements and in paper chromatographic detection of these compounds. 相似文献
18.
反相高效液相色谱法（RP-HPLC）测定冷却猪肉中生物胺 总被引：8，自引：0，他引：8
应用反相高效液相色谱法（RP-HPLC）建立同时测定冷却猪肉中多种生物胺的方法。样品经0.4 mol/L高氯酸提取后用丹磺酰氯柱前衍生,流动相为乙腈和水,采用梯度洗脱,流速为1.0 mL/min,荧光检测器激发波长（Ex）340 nm,发射波长（Em）515 nm。结果表明：采用该方法色胺、苯乙胺、腐胺、尸胺、组胺、酪胺、亚精胺和精胺8种生物胺能在25 min内得到很好分离。线性范围为0.5-20μg/mL（R^2〉0.99）,回收率在82.43%-97.14%之间,相对标准偏差RSD小于10%。 相似文献
19.
[目的]优选合适的方法定性定量地分析餐厨废弃物中5种生物胺的含量.[方法]应用紫外检测-反相高效液相色谱（RP-HPLC）技术,建立了餐厨废弃物中5种生物胺的定性定量分析方法.餐厨废弃物经三氯乙酸溶液提取后,正己烷除脂,苯甲酰氯衍生,氮吹浓缩,进行RP-HPLC检测.采用Waters RP18色谱柱（4.6 mm×150 mm,3.5μm）,流动相采用甲醇和水进行梯度洗脱,流速为0.8ml/min,柱温为30℃,紫外检测波长为254 nm.[结果]该方法在0.50～ 50.00μg/ml范围内线性关系良好（R2 ＞0.99）,5种生物胺的检测限：腐胺、尸胺为0.1 μg/ml,精胺、组胺、酪胺为0.5μg/ml.相对标准偏差（RSD）低于6％,5种生物胺的加标回收率为67％～ 120％.[结论]该方法灵敏度高,重复性和准确性好,适合餐厨废弃物中生物胺的定性定量分析. 相似文献
20.
As one of the dominant reactions occurring during thermal treatment of food, the Maillard reaction not only leads to the formation of aroma, browning color and taste compounds, but also contributes to the formation of some unpleasant toxic substances including acrylamide, heterocyclic amines and advanced glycation end products. Polyphenols, one of the most abundant antioxidants in the human diet, are contained in different kinds of foods. In this review, some recent studies on the impact of dietary polyphenols on the formation of acrylamide, heterocyclic amines and advanced glycation end products formed during the Maillard reaction are summarized, including the research work conducted with both chemical model systems and real food model systems; the possible inhibitory mechanisms of different polyphenols are also summarized and discussed in this review. Basically we found that some dietary polyphenols not only scavenge free radicals, but also react with reactive carbonyl species, thus lowering the formation of toxic Maillard reaction products. This review provides a useful theoretical foundation for the application of polyphenols in food safety, and suggests some directions for further study of natural products as inhibitors against the formation of toxic substances in thermally processed food. 相似文献