- Redox self-sufficient biocatalyst network for the amination of primary alcohols
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Driving the machinery: A biocatalytic redox-neutral cascade for the preparation of terminal primary amines from primary alcohols at the expense of ammonia has been established in a one-pot one-step method (see picture). Applying this artificial biocatalyst network, long-chain 1,ω-alkanediols were converted into diamines, which are building blocks for polymers, in up to 99 % conversion. Copyright
- Sattler, Johann H.,Fuchs, Michael,Tauber, Katharina,Mutti, Francesco G.,Faber, Kurt,Pfeffer, Jan,Haas, Thomas,Kroutil, Wolfgang
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p. 9156 - 9159
(2012/10/30)
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- Reactions of cyclopropanone acetals with alkyl azides: Carbonyl addition versus ring-opening pathways
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(Chemical Equation Presented) The Lewis acid-mediated reactions of substituted cyclopropanone acetals with alkyl azides were found to strongly depend on the structure of the ketone component. When cyclopropanone acetal was treated with alkyl azides, N-substituted 2-azetidinones and ethyl carbamate products were obtained, arising from azide addition to the carbonyl, followed by ring expansion or rearrangement, respectively. When 2,2-dimethylcyclopropanone acetals were reacted with azides in the presence of BF3· OEt2, the products obtained were α-amino-α′- diazomethyl ketones, which arose from C2-C3 bond cleavage of the corresponding cyclopropanone, giving oxyallyl cations that were captured by azides. Aryl-substituted cyclopropanone acetals, when subjected to these conditions, afforded [1,2,3]oxaborazoles exclusively, which were also the result of C2-C3 bond rupture, azide capture, and then loss of nitrogen. In the reactions of n-hexyl-substituted cyclopropanone acetals with alkyl azides, a mixture of 2-azetidinones and regioisomeric [1,2,3]-oxaborazoles was obtained. The reasons for the different behavior of the various systems are discussed.
- Grecian, Scott,Desai, Pankaj,Mossman, Craig,Poutsma, Jennifer L.,Aube, Jeffrey
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p. 9439 - 9447
(2008/03/14)
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- Pd(OAc)2-catalyzed carbonylation of amines
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A phosphine-free catalytic system [Pd(OAc)2-Cu(OAc) 2-air] induced a substrate-specific carbonylation of amines in boiling toluene under CO gas (1 atm). Symmetrical N,N′-dialkylureas were obtained by the carbonylation of primary amines. N,N,N′-Trialkylureas were selectively formed by addition of a secondary amine to the above reaction vessel. Secondary amines did not give tetraalkylureas. However, dialkylamines with a phenyl group on their alkyl chains, such as N-monoalkylated benzylic amine or phenethylamine derivatives, underwent a direct aromatic carbonylation to afford five- or six-membered benzolactams. In the carbonylation, the chelation effect or steric repulsion between Pd(II) and the meta-substituent in the ortho-palladation and the ring sizes of cyclopalladation products that were formed prior to carbonylation were found to generate good site selectivity and increase the reaction rate. In contrast, carbonylation of ω- arylalkylamines with a hydroxyl group gave neither ureas nor benzolactams but instead produced 1,3-oxazolidinones smoothly. Hydrochlorides of amines also underwent carbonylation to afford the corresponding amides under the conditions used. This procedure made it possible to prepare ureas of amino acid esters and N-alkylcarbamates in practical yields.
- Orito, Kazuhiko,Miyazawa, Mamoru,Nakamura, Takatoshi,Horibata, Akiyoshi,Ushito, Harumi,Nagasaki, Hideo,Yuguchi, Motoki,Yamashita, Satoshi,Yamazaki, Tetsuro,Tokuda, Masao
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p. 5951 - 5958
(2007/10/03)
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- A novel PdCl2/ZrO2-SO42- catalyst for synthesis of carbamates by oxidative carbonylation of amines
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At 170°C and ca. 4.0 MPa, oxidative carbonylation of aromatic amines to synthesize corresponding carbamates over a novel PdCl2/ZrO2-SO42- catalyst could proceed with high conversion and selectivity.
- Shi, Feng,Deng, Youquan,SiMa, Tianlong,Yang, Hongzhou
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p. 525 - 528
(2007/10/03)
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- Zinc promoted simple and convenient synthesis of carbamates: An easy access for amino group protection
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Synthesis of alkyl, aryl, heterocyclic, carbohydrate and amino acid carbamates is described. The protection of the amino group in the presence of other functionality in amino acids demonstrates the importance of this method.
- Yadav,Reddy, Gondi Sudershan,Reddy, M. Muralidhar,Meshram
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p. 3259 - 3262
(2007/10/03)
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- A simple method for the synthesis of carbamates
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A new method for carbamate synthesis using aryl and alkylamines with sodium hydride and diethylcarbonate in dry benzene is described.
- Angeles,Santillan,Martinez,Ramirez,Moreno,Salmon,Martinez
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p. 2441 - 2447
(2007/10/02)
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- Organoaluminum-Promoted Homologation of Ketones with Diazoalkanes
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Organoaluminum-promoted single homologation of aliphatic and aromatic ketones with diazoalkanes has been described, and among various organoaluminum reagents, especially bulky methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) is found to be highly effective for the selective homologation of various ketones.
- Maruoka, Keiji,Concepcion, Arnel B.,Yamamoto, Hisashi
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p. 4725 - 4726
(2007/10/02)
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- The reactions of organoboranes with N-chloro-N-sodiocarbamates: A novel synthesis of N-alkylcarbamates
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Trialkylboranes react with N-chloro-N-sodiocarbamates to form N-alkylcarbamates in yields ranging from 50-88%. The reaction is best carried out without intermediate isolation of the N-chlorocarbamate salt. Only one of the alkyl groups of the trialkylborane is utilized.
- Wachter-Jurcsak,Scully Jr.
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p. 5261 - 5264
(2007/10/02)
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- Chemical Ionization Mass Spectra of Urethanes
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Chemical ionization mass spectra using methane as the reagent gas are reported for 33 urethanes of general structure RNHCO2C2H5 nH2n+1 (n=1-8), CH2CH=CH2, cyclo-C6H11, Ph, PhCH2, PhCH2CH2, and Ph(CH3)CH> and R2NCO2C2H5 nH2n+1 (n=1-4)>.Abundant MH+ ions are present in all the spectra, accompanied by satellite peaks corresponding to + and +.Four classes of fragment ions are of general importance in the spectra.Two of these, + and +, are associated with the CO2C2H5 group.The other two, corresponding to alkane and alkene elimination from MH+, arise from the RNH or R2N function.The mechanisms whereby these fragment ions are formed are discussed and their analytical utility is illustrated by reference to the spectra of the four isomeric C4H9NHCO2C2H5 and the eight isomeric C5H11NHCO2C2H5 compounds.The results of 2H-labelling studies are presented and a comparison is made between the methane and ammonia chemical ionisation spectra of selected urethanes.
- Wright, Andrew D.,Bowen, Richard D.,Jennings, Keith R.
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p. 1521 - 1528
(2007/10/02)
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- Low-energy, Low-temperature Mass Spectra. 10-Urethanes
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The 12.1 eV, 75 deg C electron impact mass spectra of 24 urethanes, RNHCO2C2H5 nH2n+1 (n = 1-8), CH2=CHCH2, Ph, PhCH2 and PhCH2CH2>, and seven symmetrically disubstituted urethanes R2NCO2C2H5 (R = CnH2n+1 (n = 1-4) are reported and discussed.All 31 spectra show appreciable molecular ion peaks.For n-CnH2n+1NHCO2C2H5, M+. usually is the most abundant ion in the spectrum.A peak at m/z 102 of comparable intensity also is present; this corresponds to formal cleavage of the bond connecting the α- and β-carbon atoms in the N-alkyl group, though it is unlikely that the daughter ion has the structure (1+).In the RNHCO2C2H5 series, branching at the α-carbon atom enhances the relative abundance of the ion arising by notional α-cleavage at the expense of that of M+..Formal cleavage of the bond between β- and γ-carbon atoms occurs to some extent for +. ions; this reaction provides information on the degree of branching at the β-carbon, especially if metastable molecular ions are considered.The higher n-CnH2n+1NHCO2C2H5 (n = 5-8) urethanes exhibit two other significant ions in their mass spectra.First, there is a peak at (1+).Secondly, a peak is present at m/z 90; the most plausible structure for this ion is (1+), arising by double hydrogen transfer from the alkyl group and expulsion of a nH2n-1>. radical.Ions originating from secondary decomposition of the primary ionic species are generally of only very low abundance in these spectra.
- Bowen, Richard D.,Maccoll, Allan
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p. 113 - 122
(2007/10/02)
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