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1.
The bicyclic amidines, 1,8‐diazabicyclo [5.4.0]undec‐7‐ene (DBU) and 1,5‐diazabicyclo[4.3.0] non‐5‐ene (DBN), were used for the chemical fixation of carbon dioxide. The promotion for CO2 fixation is often reported through the formation of a thermally unstable DBU or DBN bicarbonate salt. To examine the effects of the DBU or DBN bicarbonate salt, reactions of 2‐aminobenzonitrile with the DBU salt or DBN salt in dimethylformamide (DMF) were performed at 20°C for 24 h in argon or carbon dioxide (0.1 MPa). However, in all the cases, 1H‐quinazoline‐2,4‐dione was not obtained completely. In contrast with room temperature reactions, 2‐aminobenzonitriles and DBU bicarbonate salt in DMF reacted for 4 h under high temperature (80°C) and CO2 atmosphere (0.1 MPa) gave 1H‐quinazoline‐2,4‐diones in good to excellent yields. At high‐temperature conditions, DBU bicarbonate salt is decomposed to DBU and carbon dioxide. Also, the carbonylation of 2‐aminobenzonitrile using DBU and carbon dioxide afforded 1H‐quinazoline‐2,4‐dione in good yields under similar reaction conditions. These results suggest that the combination of DBU or DBN as a strong base and carbon dioxide is much more important than the in situ formation of DBU or DBN bicarbonate salt for the acceleration of CO2 fixation. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:276–280, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21014 相似文献
2.
Rodrigo O.M.A. de Souza Vera L.P. Pereira Mario L.A. A. Vasconcellos 《Tetrahedron letters》2008,49(41):5902-5905
We have found that water and organic solvents mixed at different proportions can give good to excellent yields and short reaction times for the Morita-Baylis-Hillman reaction. The present Letter details our findings in the Morita-Baylis-Hillman reaction between several aromatic aldehydes and methyl acrylate or acrylonitrile. The selection of the catalyst was also evaluated and DABCO affored the best results when compared to DBU, DMAP, HMT, Imidazole and Triethylamine. 相似文献
3.
DMAP, DBU, and quinuclidine efficiently promote novel hydroalkoxylation reactions of acrylamide in primary alcohol solvents. DABCO is a comparatively poor hydroalkoxylation promoter and can effect clean, selective Baylis-Hillman reactions between acrylamide and aldehydes in alcoholic/aqueous media in which more basic nucleophilic catalysts promote hydroalkoxylation preferentially. Optimization of the reaction conditions has allowed acrylamide to be reacted with a range of aromatic aldehydes in moderate to excellent yields, including the first examples involving deactivated, electron-rich substrates such as p-tolualdehyde and o-anisaldehyde. 相似文献
4.
Mechanisms of DABCO‐ and DMAP‐catalyzed [2 + 4] cycloaddition reactions of methylallenoate with methyleneindolonone: A DFT study
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The mechanisms and stereoselectivities of the [2 + 4] cycloaddition reaction of methylallenoate R1 with methyleneindolonone R2 catalyzed by DABCO (Equation 1) and DMAP (Equation 2) organocatalysts have been examined with density functional theory (M06‐2X) calculations. Several possible reaction pathways (paths 1a, 1b, and 1c for Equation 1 and paths 2a and 2b for Equation 2) were located and compared. The results of our study reveal that for both reactions, three reaction stages have been characterized: nucleophilic addition of the catalyst ( DABCO or DMAP ) to R1 (Stage I ), addition of the other reactant R2 (Stage II ), intramolecular cycloaddition and liberation of the catalyst ( DABCO or DMAP ) afforded the final product (Stage III ). For the DABCO ‐catalyzed cycloaddition, we predict that path 1a leading to P(E) is the most energy favorable pathway among the three possible pathways. The carbon–carbon bond formation step is the rate‐determining step (ΔG ?=23.6 kcal/mol). With DMAP catalyst, the same reaction gave P(Z) as the major product. The barrier for the rate‐determining step (addition of R1 to DMAP ) is 25.8 kcal/mol. The calculated results are in agreement with the experimental findings. Moreover, for both reactions, the analysis of global reactivity indexes has been carried out to examine the role of catalyst. The present study should provide a general mechanistic framework for the rational design of this kind of reactions. 相似文献
5.
6.
Prof. Henning Hopf Prof. Peter G. Jones Dr. Alina Nicolescu Prof. Elena Bicu Dr. Lucian M. Birsa Dr. Dalila Belei 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(19):5565-5568
A facile synthesis of Pechmann dyes has been accomplished by the reaction of substituted N‐phenacyl‐4‐dimethylaminopyridinium halides with dimethyl maleate in the presence of DBU. Based on a related 4‐DMAP elimination product and an isolated monolactone intermediate a reaction mechanism has been proposed. The scope of this synthetic method is determined by the availability of α‐haloaroyl or heteroaroyl derivatives. DBU=1,8‐diazabicycloundec‐7‐ene, DMAP=4‐dimethylaminopyridine. 相似文献
7.
New acid/base salts as co‐catalysts for the organocatalyzed ring opening polymerization of lactide
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Yong Miao Nicholas Stanley Audrey Favrelle Till Bousquet Marc Bria André Mortreux Philippe Zinck 《Journal of polymer science. Part A, Polymer chemistry》2015,53(5):659-664
(R)‐(+)‐binaphathyl‐diyl hydrogen phosphate (BNPH)/ diazabicyclo[5.4.0]undec‐7‐ene (DBU) and (1R)‐(?)?10‐camphorsulfonic acid (CSA)/4‐dimethylaminopyridine (DMAP) acid–base salts were synthesized and assessed for the ring‐opening polymerization of rac‐lactide. They were found to be inactive toward the polymerization in the presence of a protic initiator. When used in combination with a base such as DBU or DMAP and a protic initiator, these acid/base conjugates led to well‐controlled polymerization in mild conditions (DM < 1.1 in all cases). With DBU, the presence of the salt was found to lead to narrower molecular weight distributions than those obtained using the base alone, and to prevent undesirable transesterification reactions occurring at the end of the reaction. An increase in activity was observed using the salts in combination with DMAP as compared with DMAP alone, together with an improvement of the control over the molecular weight. The results were discussed on the basis of 1H nuclear magnetic resonance analyzes including acid/base equilibria involving the use of two different bases. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 659–664 相似文献
8.
Zhenshan Jia Xiang Zhang Gaihong Zhang Shaohua Huang Hao Fang Xiangqing Hu Yuliang Li Prof. Liangbing Gan Prof. Shiwei Zhang Prof. Daoben Zhu Prof. 《化学:亚洲杂志》2007,2(2):290-300
The Cs‐symmetric fullerene chlorohydrin C60(Cl)(OH)(OOtBu)4 reacts with 4‐dimethylaminopyridine (DMAP) and 1,4‐diazabicyclo[2.2.2]octane (DABCO) to yield two isomers with the formula C60(O)(OOtBu)4 in good yields. These isomers differ with respect to the location of the epoxy functionality. The one from DMAP is Cs symmetric, whereas that from DABCO is C1 symmetric with the epoxy group on the central pentagon. Two different mechanisms are proposed to explain the chemoselectivity of these reactions. The reaction with DMAP involves single‐electron transfer as the key step; DMAP acts as the electron donor. A combination of an oxygen‐atom shift and SN2′′ processes (boomerang substitution) are responsible for the formation of isomer with DACBO. Various related reactions support the proposed mechanisms. The structures of new fullerene derivatives were determined by spectroscopy, single‐crystal X‐ray analysis, and chemical correlation experiments. 相似文献
9.
De Rycke N Couty F David OR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(46):12852-12871
This review article presents how nitrogen-centred Lewis bases were modified in order to increase their reactivity in catalytic processes. As examples, we focus on alcohol acylation and Morita-Baylis-Hilman reactions in order to showcase the fundamental parameters at play in transformations initiated by catalysts bearing respectively an active sp(2) or sp(3) nitrogen atoms. These two aspects are epitomised by two leading compounds, the Steglich base 4-dimethylaminopyridine (DMAP), and 1,4-diazabicyclo[2.2.2]octane (DABCO). Throughout this review, we stress the role played and the information brought by physical organic chemistry. Comprehension of these complex transformations relies on the fundamental knowledge of parameters, such as, nucleophilicity, nucleofugality, Lewis basicity, and crucially also the knowledge of their divergent impacts on each elementary step of the catalytic cycle. 相似文献
10.
In the Baylis-Hillman reaction of N-benzylidene-4-methyl-benzenesulfonamide with cyclohex-2-en-1-one or cyclopent-2-en-1-one, we found that, in the presence of a catalytic amount of DMAP, the Baylis-Hillman reaction can be greatly accelerated to give the normal Baylis-Hillman adduct 1 or 3 in good or very high yields: moreover, using PBu3 as a Lewis base in the reaction of N-benzylidene-4-methylbenzenesulfonamide with cyclopent-2-en-1-one, the normal Baylis-Hillman adducts 3 could be obtained in very high yields within 5 h, however, using PBu3 or DBU as a Lewis base in the reaction of N-benzylidene-4-methyl-benzenesulfonamide with cyclohex-2-en-1-one, beside the normal Baylis-Hillman adduct 1 abnormal Baylis-Hillman adduct 3-aryl-2-[(4-methylphenyl)sulfonyl]-2-azabicyclo[2.2.2]octan-5-one 2 was formed at the same time; the substituent's effects were also examined. 相似文献
11.
Wen-Chung Shieh Mario LozanovMauricio Loo Oljan Repi?Thomas J. Blacklock 《Tetrahedron letters》2003,44(24):4563-4565
An environmentally friendly process for the benzylation of nitrogen, oxygen, or sulfur atoms with dibenzyl carbonate has been developed. Catalytic amounts of DABCO or DBU can accelerate this ‘green’ alkylation. 相似文献
12.
Lucyna A. Woźniak Arkadiusz Chworoś Wojciech J. Stec 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract Miwed phosphorus-carboxylic anhydrides have demonstrated both acylating and phosphorylating properties.[1] Here we report the reactivity of O,O-diethyl(O-2,4,6-trimethylbenzoyl) phosphates (1), and O-methyl (O-2,4,6-trimetyIbenzoyl) dimethylphosphonates (2)with nucleophiles in the presence of different strong organic bases (DBU, DMAP). 相似文献
13.
Only supercritical carbon dioxide (scCO2) as a reactant and a solvent, and catalytic amount of base (DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), DBN (1,5-diazabicyclo[4.3.0]non-5-ene), Dabco® (1,4-diazabicyclo[2.2.2]octane), and triethylamine) afforded 1H-quinazoline-2,4-diones in good to excellent yields from 2-aminobenzonitriles. 6,7-Dimethoxy-1H-quinazoline-2,4-dione, which is a key intermediate of medicines (Prazosin, Bunazosin, and Doxazosin) was synthesized successfully in a 97% yield, using 0.1 equiv of DBU under scCO2 (10 MPa) at 80 °C. 相似文献
14.
1,5-Diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) react with chloro- and dichloro-phosphines leading to onio- and dionio-substituted phosphines. Similarly, onio-substituted silicon and tin derivatives are prepared; they are used as onio-substituent transfer reagents in the synthesis of a trionio-substituted phosphine. 相似文献
15.
Alkyl and aryl amines are converted smoothly to the corresponding isothiocyanates via the dithiocarbamates in good to excellent yields using di-tert-butyl dicarbonate (Boc2O) and 1-3 mol % of DMAP or DABCO as catalyst. As most of the byproducts are volatile, the work-up involves simple evaporation of the reaction mixture. 相似文献
16.
Basavaiah D Sharada DS Kumaragurubaran N Reddy RM 《The Journal of organic chemistry》2002,67(20):7135-7137
The Baylis-Hillman coupling between activated alkenes and alkyl 2-(bromomethyl)prop-2-enoates in the presence of DABCO (or DBU) leading to the formation of 2,4-functionalized 1,4-pentadienes, has been described. 相似文献
17.
Phosphate protection in the phosphotriester approach is improved by the new, versatile p-nitrophenylethyl group due to its stability in the condensation step and its clean removal by DBU and DBN respectively. 相似文献
18.
Florine Chanthavong 《Tetrahedron letters》2006,47(12):1909-1912
Traditionally, mineral bases are used in Suzuki coupling protocols. The use of DBU or DABCO as alternative bases for the reaction is reported and the application discussed. 相似文献
19.
Chun-Bao Miao Rui Liu Yan-Fang Sun Xiao-Qiang Sun Hai-Tao Yang 《Tetrahedron letters》2017,58(6):541-545
A base-controlled formal [3 + 2] cycloaddition of 1,3-dicarbonyl compounds to enones via an I2-mediated cyclization was reported. Highly functionalized dihydrofurans and furans were selectively obtained under I2/DMAP and I2/DBU conditions in the cyclization step, respectively. 相似文献
20.
Jacqueline Goddat Partha Datta Arthur A. Grey Jeremy R Carver Rajan N. Shah 《Journal of carbohydrate chemistry》2013,32(6):793-800
Abstract The title compound was prepared by first converting trideuteriomethyl 2,3,4-tri-O-benzyl-β-D-mannopyranoside to a 6-bromo-6-deoxy derivative which on elimination by using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) or DBN (1,5-diazabi-cyclo[4.3.0]non-5-ene) gave a hex-5-enopyranoside derivative. The deuteroboration of the hex-5-enopyranoside followed by oxidation and subsequent deblocking produced trideuteriomethyl 5-deuterium-β-D-mannopyranoside. 相似文献