- Microwave-mediated Newman-Kwart rearrangement in water
-
For the first time the unimolecular Newman-Kwart rearrangement is performed in pure water. The elevated temperatures required for the 1,3-aryl shift are easily accomplished by microwave irradiation. Differently functionalized substrates underline the expe
- Hoffmann, Ina,Schatz, Jürgen
-
p. 80692 - 80699
(2016/09/09)
-
- Tailored near-infrared contrast agents for image guided surgery
-
The success of near-infrared (NIR) fluorescence to be employed for intraoperative imaging relies on the ability to develop a highly stable, NIR fluorescent, nontoxic, biocompatible, and highly excreted compound that retains a reactive functionality for co
- Njiojob, Costyl N.,Owens, Eric A.,Narayana, Lakshminarayana,Hyun, Hoon,Choi, Hak Soo,Henary, Maged
-
p. 2845 - 2854
(2015/04/14)
-
- Sintered silicon carbide: A new ceramic vessel material for microwave chemistry in single-mode reactors
-
Silicon carbide (SiC) is a strongly microwave absorbing chemically inert ceramic material that can be utilized at extremely high temperatures due to its high melting point and very low thermal expansion coefficient. Microwave irradiation induces a flow of electrons in the semiconducting ceramic that heats the material very efficiently through resistance heating mechanisms. The use of SiC carbide reaction vessels in combination with a single-mode microwave reactor provides an almost complete shielding of the contents inside from the electromagnetic field. Therefore, such experiments do not involve electromagnetic field effects on the chemistry, since the semiconducting ceramic vial effectively prevents microwave irradiation from penetrating the reaction mixture. The involvement of electromagnetic field effects (specific/nonthermal microwave effects) on 21 selected chemical transformations was evaluated by comparing the results obtained in microwave-transparent Pyrex vials with experiments performed in SiC vials at the same reaction temperature. For most of the 21 reactions, the outcome in terms of conversion/purity/product yields using the two different vial types was virtually identical, indicating that the electromagnetic field had no direct influence on the reaction pathway. Due to the high chemical resistance of SiC, reactions involving corrosive reagents can be performed without degradation of the vessel material. Examples include high-temperature fluorine-chlorine exchange reactions using triethylamine trihydrofluoride, and the hydrolysis of nitriles with aqueous potassium hydroxide. The unique combination of high microwave absorptivity, thermal conductivity, and effusivity on the one hand, and excellent temperature, pressure and corrosion resistance on the other hand, makes this material ideal for the fabrication of reaction vessels for use in microwave reactors. Simulating conductive heat transfer in a microwave: Using reaction vials made out of strongly microwave-absorbing silicon carbide (SiC) in a microwave reactor simulates a conductively heated autoclave experiment due to efficient shielding of the electromagnetic field by the SiC vial. Advantages of SiC vials for microwave processing include their excellent corrosion resistance, thermal stability, and high thermal effusivity and conductivity.
- Gutmann, Bernhard,Obermayer, David,Reichart, Benedikt,Prekodravac, Bojana,Irfan, Muhammad,Kremsner, Jennifer M.,Kappe, C. Oliver
-
supporting information; experimental part
p. 12182 - 12194
(2011/02/23)
-
- Continuous-Flow microreactor Chemistry under High-Temperature/pressure
-
High-temperature organic synthesis can be performed under continuous-flow conditions in a stainless steel microtubular flow reactor capable of achieving temperatures of 350 °C and 200 bar. Under these extreme experimental environments transformations normally performed in a high-boiling solvent at reflux temperature - or under sealed-vessel microwave conditions - can be readily converted to a flow regime by using lower boiling solvents in or near their supercritical state. Wiley-VCH Verlag GmbH & Co, KGaA.
- Razzaq, Tahseen,Glasnov, Toma N.,Kappe, C. Oliver
-
supporting information; experimental part
p. 1321 - 1325
(2009/07/26)
-
- Microwave chemistry in silicon carbide reaction vials: Separating thermal from nonthermal effects
-
Running oil-bath chemistry in a microwave! Using reaction vials made out of strongly microwave-absorbing silicon carbide (SiC) in a microwave reactor simulates experiments conducted in an autoclave with conductive heating because of the efficient shielding of the electromagnetic field by the SiC vial. This technology makes it possible to study the significance of microwave effects.
- Obermayer, David,Gutmann, Bernhard,Oliver Kappe
-
supporting information; scheme or table
p. 8321 - 8324
(2010/01/06)
-
- 6-ARYLALKYLAMINO- 2,3,4,5-TETRAHYDRO-1H-BENZO[D]AZEPINES AS 5-HT2C RECEPTOR AGONISTS
-
The present invention provides 6-substituted 2,3,4,5-tetrahydro-lH- benzo[d]azepines of Formula (I) as selective 5-HT2c receptor agonists for the treatment of 5-HT2c associated disorders including obesity, obsessive/compulsive disorder, depression, and anxiety, where, R6 is -NR10R11, where R10 is substituted phenylalkyl or substituted pyridylalkyl and other substituents are as defined in the specification.
- -
-
Page/Page column 128
(2010/11/26)
-
- The importance of agitation and fill volume in small scale scientific microwave reactors
-
The effect of agitation and fill volume in a microwave tube on the rate of homogenous reaction solutions under both stirred and unstirred conditions is reported. Significant increases in rate are found in two different microwave instruments when the homog
- Moseley, Jonathan D.,Lenden, Philip,Thomson, Anthony D.,Gilday, John P.
-
p. 6084 - 6087
(2008/03/12)
-
- The Newman-Kwart rearrangement re-evaluated by microwave synthesis
-
The Newman-Kwart rearrangement (NKR) has been re-evaluated by microwave heating. Microwave technology has proven to be ideal for investigating this high temperature rearrangement and facilitated the confirmation of many aspects of this valuable reaction.
- Moseley, Jonathan D.,Sankey, Rosalind F.,Tang, Olivier N.,Gilday, John P.
-
p. 4685 - 4689
(2007/10/03)
-
- Effects of aromatic thiols on thiol-disulfide interchange reactions that occur during protein folding
-
The folding of disulfide containing proteins from denatured protein to native protein involves numerous thiol-disulfide interchange reactions. Many of these reactions include a redox buffer, which is a mixture of a thiol (RSH) and the corresponding disulfide (RSSR). The relationship between the structure of RSH and its efficacy in folding proteins in vitro has been investigated only to a limited extent. Reported herein are the effects of aliphatic and especially aromatic thiols on reactions that occur during protein folding. Aromatic thiols may be particularly efficacious as their thiol pKa values and reactivities match those of the in vivo catalyst, protein disulfide isomerase (PDI). This investigation correlates the thiol pKa values of aromatic thiols with their reactivities toward small molecule disulfides and the protein insulin. The thiol pKa values of nine para-substituted aromatic thiols were measured; a Hammett plot constructed using σp- values yielded ρ = -1.6 ± 0.1. The reactivities of aromatic and aliphatic thiols with 2-pyridyldithioethanol (2-PDE), a small molecule disulfide, were determined. A plot of reactivity versus pKa of the aromatic thiols had a slope (β) of 0.9. The ability of these thiols to reduce (unfold) the protein insulin correlates strongly with their ability to reduce 2-PDE. Since the reduction of protein disulfides occurs during protein folding to remove mismatched disulfides, aromatic thiols with high pKa values are expected to increase the rate not only of protein unfolding but protein folding as well.
- DeCollo,Lees
-
p. 4244 - 4249
(2007/10/03)
-
- Rapid and Selective Reduction of Functionalized Aromatic Disulfides with Lithium Tri-tert-butoxyaluminohydride. A Remarkable Steric and Electronic Control. Comparison of Various Hydride Reagents
-
Lithium tri-tert-butoxyaluminohydride (LTBA), an exceptionally mild reducing agent in organic synthesis, reduces functionalized aromatic disulfides to the corresponding thiols in quantitative yield.The reaction is rapid (for example, o-tolyl disulfide is reduced to completion in 60 min at 25 deg C) and can tolerate a wide variety of functional groups, such as halogen, nitro, carboxylic acid, and their derivatives.The presence of electron-withdrawing substituents dramatically enhances the rate of reduction (p-chlorophenyl disulfide is quantitatively reduced in 30 s) and electron-releasing substituents diminishes the rate of cleavage.The reaction is sensitive to steric effects (2,4-di-tert-pentylphenyl disulfide underwent 25percent reduction in 24 h).However, such hindered disulfides can be rapidly and quantitatively reduced in refluxing THF.The reaction of LTBA with alkyl disulfides is extremely sluggish.The reaction provides a useful and simple means for the facile and selective reduction of aromatic disulfides where this is required in synthetic operations.
- Krishnamurthy, S.,Aimino, D.
-
p. 4458 - 4462
(2007/10/02)
-
- Benzonitrile and benzothiocyano intermediates
-
There are described compounds of the formula STR1 in which R1 is hydrogen or C1-6 alkyl, R2 is hydrogen, C1-6 alkyl or C3-6 alkenyl, X and Y are each oxygen, sulphur, sulphinyl or sulphonyl, n is 2 to
- -
-
-