Co-reporter:Song Yao;Kaijing Zhou;Jiabing Wang;Hongen Cao;Lei Yu;Jianzhang Wu;Peihong Qiu
Green Chemistry (1999-Present) 2017 vol. 19(Issue 13) pp:2945-2951
Publication Date(Web):2017/07/03
DOI:10.1039/C7GC00977A
By using air as the superior oxidant, a highly atom-efficient synthesis of 2-substituted quinazolines is developed by a CsOH-mediated direct aerobic oxidative reaction of the readily available and stable 2-aminoarylmethanols and nitriles. Effectively working as the promoter in the alcohol oxidation, nitrile hydration, and cyclocondensation steps, CsOH is the best base for the reaction. A similar method can also be extended to the synthesis of substituted quinolines starting from methyl ketones instead of nitriles.
Co-reporter:Jianhui Chen;Yang Li;Shuangyan Li;Jianping Liu;Fei Zheng;Zhengping Zhang
Green Chemistry (1999-Present) 2017 vol. 19(Issue 3) pp:623-628
Publication Date(Web):2017/02/06
DOI:10.1039/C6GC02518H
By using aldehydes or ketones as the catalyst and screening CsOH out as the more effective base than KOH in many instances, an efficient 9-C-alkylation of fluorenes with alcohols was achieved to provide a green and practical method for general synthesis of the useful 9-monoalkylated fluorenes in high selectivities. This new method tolerates a wide range of substrates including activated and unactivated primary and secondary alcohols, thus solving the issues remaining in the field and largely broadening the diversity of the 9-monoalkylated fluorenes. Consequently, fine-tuning of the alkylated fluorenes was made possible to provide specific fluorene monomers for function-oriented polyfluorenes. Preliminary mechanistic studies revealed that the external carbonyl compounds can be quantitatively regenerated and recovered in the reaction cycle.
Co-reporter:Yaqi Yang;Zihang Ye;Xu Zhang;Yipeng Zhou;Xiantao Ma;Hongen Cao;Huan Li;Lei Yu
Organic & Biomolecular Chemistry 2017 vol. 15(Issue 45) pp:9638-9642
Publication Date(Web):2017/11/22
DOI:10.1039/C7OB02461D
Alcohols can be efficiently converted into the useful thioethers by a transition metal- and base-free dehydrative S-alkylation reaction with thiols or disulfides by employing alkyl halides as the effective catalyst. This simple and efficient method is a green and practical way for the preparation of thioethers, as it tolerates a wide range of substrates such as aryl and alkyl thiols, as well as benzylic, allylic, secondary, tertiary, and even the less reactive aliphatic alcohols.
Co-reporter:Xiantao Ma;Lei Yu;Chenliang Su;Yaqi Yang;Huan Li
Advanced Synthesis & Catalysis 2017 Volume 359(Issue 10) pp:1649-1655
Publication Date(Web):2017/05/17
DOI:10.1002/adsc.201700227
AbstractA metal- and base-free three-component coupling of alcohols, heteroaryl halides, and thiourea has been developed for direct and selective synthesis of heteroaryl thioethers. This method can be easily scaled up to the gram scale and extended to dialkyl thioethers, heteroaryl selenides, benzothiazoles, and some antimycobacterially-active thioethers. Mechanistic studies revealed that a by-product-promoted in situ C–O activation of alcohols to more reactive alkyl halides and slow release of the thiol and alkyl halide intermediates are the key to the high selectivity and success of the reaction.
Co-reporter:Qing Xu, Huamei Xie, Er-Lei Zhang, Xiantao Ma, Jianhui Chen, Xiao-Chun Yu and Huan Li
Green Chemistry 2016 vol. 18(Issue 14) pp:3940-3944
Publication Date(Web):21 Apr 2016
DOI:10.1039/C6GC00938G
Using only catalytic amounts of alkyl halides in the reactions of poor nucleophilic amines/amides and alcohols led to a selective Hofmann N-alkylation reaction catalytic in alkyl halides, providing a practical and efficient method for the practical synthesis of mono- or di-alkylated amines/amides in high selectivities. This new method avoids the use of large amounts of bases, alkyl halides, and solvents, and generates water as the only byproduct. Preliminary mechanistic studies showed that alkyl halides are key intermediates/catalysts regeneratable in the reaction cycle.
Co-reporter:Xiantao Ma, Quan Liu, Xiaojuan Jia, Chenliang Su and Qing Xu
RSC Advances 2016 vol. 6(Issue 62) pp:56930-56935
Publication Date(Web):07 Jun 2016
DOI:10.1039/C6RA10517C
An efficient alkali hydroxide-mediated SNAr reaction of heteroaryl halides has been developed for the practical synthesis of the useful unsymmetrical heteroaryl thioethers and chalcogenides. The usually odorless, easily available, lowly toxic, and easily stored and handled diorganyl dichalcogenides can be used as safer and convenient chalcogen nucleophile precursors and diverse unsymmetrical heteroaryl chalcogenides can be obtained in good to high yields by the method.
Co-reporter:Xiaohui Li, Shuangyan Li, Qiang Li, Xu Dong, Yang Li, Xiaochun Yu, Qing Xu
Tetrahedron 2016 Volume 72(Issue 2) pp:264-272
Publication Date(Web):14 January 2016
DOI:10.1016/j.tet.2015.11.016
We developed simple and practical N-alkylation reactions of amines and sulfinamides with primary and secondary alcohols by using only catalytic amounts of air as the initiator without adding any external catalysts. This method has advantages of simple conditions, easy operation, and comparatively wider scope of substrates, providing an efficient and green catalyst-free-like alcohol-based dehydrative N-alkylation method. Mechanistic studies revealed that air initiated the reactions by aerobic oxidation of the alcohols to the key initiating aldehydes or ketones in the presence of bases.We developed simple and practical N-alkylation reactions of amines and sulfinamides with primary and secondary alcohols by using only catalytic amounts of air as the initiator without adding any external catalysts. This method has advantages of simple conditions, easy operation, and comparatively wider scope of substrates, providing an efficient and green catalyst-free-like alcohol-based dehydrative N-alkylation method. Mechanistic studies revealed that air initiated the reactions by aerobic oxidation of the alcohols to the key initiating aldehydes or ketones in the presence of bases.
Co-reporter:Qiang Li;Dr. Tieqiao Chen;Dr. Qing Xu;Dr. Li-Biao Han
Chemistry - A European Journal 2016 Volume 22( Issue 18) pp:6213-6217
Publication Date(Web):
DOI:10.1002/chem.201600115
Abstract
Optically active α-hydroxyphosphinates with both C- and P-stereogenic centers are obtained by rhodium- or iridium-catalyzed substrate-directed stereoselective addition of the optically pure H-phosphinates to aldehydes. The reaction most probably proceeds by a transition-metal-catalyzed mechanism with hydridometal complexes as key intermediates in the catalytic cycle.
Co-reporter:Qing Xu, Huamei Xie, Pingliang Chen, Lei Yu, Jianhui Chen and Xingen Hu
Green Chemistry 2015 vol. 17(Issue 5) pp:2774-2779
Publication Date(Web):20 Mar 2015
DOI:10.1039/C5GC00284B
Organohalides are found to be effective catalysts for dehydrative O-alkylation reactions between alcohols, providing selective, practical, green, and easily scalable homo- and cross-etherification methods for the preparation of useful symmetrical and unsymmetrical aliphatic ethers from the readily available alcohols. Mechanistic studies revealed that organohalides are regenerated as reactive intermediates and recycled to catalyze the reactions.
Co-reporter:Shuangyan Li, Xiaohui Li, Qiang Li, Qiaochao Yuan, Xinkang Shi and Qing Xu
Green Chemistry 2015 vol. 17(Issue 6) pp:3260-3265
Publication Date(Web):13 Feb 2015
DOI:10.1039/C4GC02542C
Catalyst-free autocatalyzed dehydrative N-alkylation reactions of 2-aminobenzothiazoles, 2-aminopyrimidines, and 2-aminopyrazine with primary and secondary alcohols have been achieved for efficient, practical, and green synthesis of the versatile heteroaryl amine derivatives. These reactions were interestingly induced by structure-dependent tautomeric equilibria of the heteroaryl amines via MPV–O transfer hydrogenation of the imino tautomers by alcohols to give aldehydes as the key initiating step.
Co-reporter:Xu Zhang;Jianqing Ye;Lei Yu;Xinkang Shi;Ming Zhang;Mark Lautens
Advanced Synthesis & Catalysis 2015 Volume 357( Issue 5) pp:955-960
Publication Date(Web):
DOI:10.1002/adsc.201400957
Co-reporter:Lei Yu, Mingxuan Liu, Fenglin Chen and Qing Xu
Organic & Biomolecular Chemistry 2015 vol. 13(Issue 31) pp:8379-8392
Publication Date(Web):09 Jun 2015
DOI:10.1039/C5OB00868A
The discovery of a series of novel organic reactions has made methylenecyclopropanes (MCPs) some of the most popular building blocks in synthetic organic chemistry during the past two decades. Among reported works, the construction of heterocycles from MCPs has highlighted new synthetic methodologies that afford more opportunities for the quick synthesis of elaborately substituted products, and this should draw a great deal of attention. However, reviews in this area are insufficient, and the latest monograph on heterocycle synthesis from MCPs was published 12 years ago. This review aims to summarize the novel organic reactions of MCPs to produce heterocycles published in recent years, which have provided specific and powerful tools for organic synthesis.
Co-reporter:Lei Yu, Jie Luan, Lin Xu, Yuanhua Ding, Qing Xu
Tetrahedron Letters 2015 Volume 56(Issue 44) pp:6116-6119
Publication Date(Web):28 October 2015
DOI:10.1016/j.tetlet.2015.09.088
Using l-proline catalyst, the useful building blocks 2-methylenecyclobutanones (2-MCBones) are now easily accessible in moderate to good yields through the condensation of the commercially available cyclobutanone with the abundant aldehydes. Compared with the literature reports, this methodology provides a direct synthesis of 2-MCBones from accessible starting materials and employs near neutral catalysts, which are stable to the acidic impurities in substrates.
Co-reporter:Xinkang Shi;Junmei Guo;Dr. Jianping Liu; Mingde Ye ;Dr. Qing Xu
Chemistry - A European Journal 2015 Volume 21( Issue 28) pp:9988-9993
Publication Date(Web):
DOI:10.1002/chem.201501184
Abstract
tBuONa-catalyzed direct aerobic oxidative cyclocondensation reactions of readily available alcohols and o-thio/hydroxy/aminoanilines under air have been developed and provide an efficient, practical, and green method for the synthesis of benzazoles. Mechanistic studies revealed that o-substituted anilines promote the initial aerobic alcohol-oxidation step, which explains the high reactivity and success of this unexpectedly simple and practical cyclocondensation method.
Co-reporter:Lei Yu, Yaping Huang, Zheng Wei, Yuanhua Ding, Chenliang Su, and Qing Xu
The Journal of Organic Chemistry 2015 Volume 80(Issue 17) pp:8677-8683
Publication Date(Web):August 14, 2015
DOI:10.1021/acs.joc.5b01358
Using air as the oxidant instead of the traditionally employed persulfates, the smaller and more uniform Pd nanoparticles (around 2 nm) supported on polyaniline (Pd@PANI) can be easily fabricated by the oxidation–polymerization of aniline with PdCl2. This material is an efficient and environmentally friendly catalyst for Heck reactions due to its recyclability, low loading, and ligand-free and mild reaction conditions. It was even tolerant to sulfur-containing substrates. This work reports the Pd@PANI-catalyzed Heck reactions with very wide substrate scopes, and discloses the catalytic mechanisms based on experimental findings and results of catalyst analysis and characterization.
Co-reporter:Lei Yu, Yulan Wu, Hongen Cao, Xu Zhang, Xinkang Shi, Jie Luan, Tian Chen, Yi Pan and Qing Xu
Green Chemistry 2014 vol. 16(Issue 1) pp:287-293
Publication Date(Web):10 Oct 2013
DOI:10.1039/C3GC41562G
2-Methylenecyclobutanones (2-MCBones), used to be difficult to access, but can now be easily achieved by a green and stereospecific Ca(OH)2-catalyzed direct and simple aldol condensation of cyclobutanone and aldehydes under mild conditions. The obtained (E)-2-MCBones should be a class of potentially useful building blocks in synthesis as they could readily undergo an interesting (PhSe)2-catalyzed Baeyer–Villiger (BV) oxidation with H2O2 at room temperature to give the versatile 4-methylenebutanolides. Mechanistic studies revealed that the BV reaction most possibly proceeded via the initial formation of benzeneseleninoperoxoic anhydride [PhSe(O)O]2O, which then converted to benzeneseleninoperoxoic acid PhSe(O)OOH as the active oxidant, followed by its selective addition to the CO bond of 2-MCBones and then a selective C–C bond cleavage and rearrangement to give 4-methylenebutanolides.
Co-reporter:Haonan Chen, Wujie Dai, Yi Chen, Qing Xu, Jianhui Chen, Lei Yu, Yajuan Zhao, Mingde Ye and Yuanjiang Pan
Green Chemistry 2014 vol. 16(Issue 4) pp:2136-2141
Publication Date(Web):02 Jan 2014
DOI:10.1039/C3GC42310G
Unexpected dimethylsulfinyl anions (I), generated in situ from the superbase system CsOH–DMSO, was found to be a highly active catalyst for controllable nitrile hydration reactions in water, which selectively afforded the versatile amides via interesting Cs-activated I-catalyzed direct and indirect hydration mechanisms involving an O-transfer process from DMSO onto the nitriles.
Co-reporter:Lei Yu, Hongyan Li, Xu Zhang, Jianqing Ye, Jianping Liu, Qing Xu, and Mark Lautens
Organic Letters 2014 Volume 16(Issue 5) pp:1346-1349
Publication Date(Web):February 24, 2014
DOI:10.1021/ol500075h
Areneselenenic acids (ArSeOH), readily generated from diaryl diselenides and H2O2 by in situ oxidation, were found to be effective and reusable catalysts for dehydration of aldoximes, leading to a practical and scalable preparation of useful organonitriles under mild conditions.
Co-reporter:Dr. Qing Xu;Jianhui Chen;Haiwen Tian;Xueqin Yuan;Shuangyan Li;Chongkuan Zhou ;Dr. Jianping Liu
Angewandte Chemie International Edition 2014 Volume 53( Issue 1) pp:225-229
Publication Date(Web):
DOI:10.1002/anie.201308642
Abstract
Direct dehydrative α-alkylation reactions of ketones with alcohols are now realized under simple, practical, and green conditions without using external catalysts. These catalyst-free autocatalyzed alkylation methods can efficiently afford useful alkylated ketone or alcohol products in a one-pot manner and on a large scale by CC bond formation of the in situ generated intermediates with subsequent controllable and selective Meerwein–Pondorf–Verley–Oppenauer-type redox processes.
Co-reporter:Dr. Qing Xu;Jianhui Chen;Haiwen Tian;Xueqin Yuan;Shuangyan Li;Chongkuan Zhou ;Dr. Jianping Liu
Angewandte Chemie 2014 Volume 126( Issue 1) pp:229-233
Publication Date(Web):
DOI:10.1002/ange.201308642
Abstract
Direct dehydrative α-alkylation reactions of ketones with alcohols are now realized under simple, practical, and green conditions without using external catalysts. These catalyst-free autocatalyzed alkylation methods can efficiently afford useful alkylated ketone or alcohol products in a one-pot manner and on a large scale by CC bond formation of the in situ generated intermediates with subsequent controllable and selective Meerwein–Pondorf–Verley–Oppenauer-type redox processes.
Co-reporter:Lei Yu, Yulan Wu, Tian Chen, Yi Pan, and Qing Xu
Organic Letters 2013 Volume 15(Issue 1) pp:144-147
Publication Date(Web):December 18, 2012
DOI:10.1021/ol3031846
Direct [3 + 2] radical cycloaddition of methylenecyclopropanes and elemental chalcogens (S, Se, Te) can readily occur under simple thermal conditions, providing an efficient, practical method for preparation of useful but not easily accessed methylene-1,2-dichalcogenolanes.
Co-reporter:Erlei Zhang, Haiwen Tian, Sendong Xu, Xiaochun Yu, and Qing Xu
Organic Letters 2013 Volume 15(Issue 11) pp:2704-2707
Publication Date(Web):May 17, 2013
DOI:10.1021/ol4010118
Abundant and cheap iron readily catalyzed the aerobic oxidative reactions of primary amines, secondary amines, benzylamines with anilines, and alcohols with amines by directly using air as the economic and safe oxidant, providing several direct, practical, and greener approaches for the preparation of useful imines.
Co-reporter:Qing Xu;Qiang Li;Xiaogang Zhu ;Jianhui Chen
Advanced Synthesis & Catalysis 2013 Volume 355( Issue 1) pp:73-80
Publication Date(Web):
DOI:10.1002/adsc.201200881
Abstract
In contrast to the borrowing hydrogen-type N-alkylation reactions, in which alcohols were activated by transition metal-catalyzed anaerobic dehydrogenation, the addition of external aldehydes was accidentally found to be a simple and effective protocol for alcohol activation. This interesting finding subsequently led to an efficient and green, practical and scalable aldehyde-catalyzed transition metal-free dehydrative N-alkylation method for a variety of amides, amines, and alcohols. Mechanistic studies revealed that this reaction most possibly proceeds via a simple but interesting transition metal-free relay race mechanism.
Co-reporter:Qing Xu;Jianhui Chen ;Quan Liu
Advanced Synthesis & Catalysis 2013 Volume 355( Issue 4) pp:697-704
Publication Date(Web):
DOI:10.1002/adsc.201200996
Abstract
Different to the borrowing hydrogen strategy in which alcohols were activated by transition metal-catalyzed anaerobic dehydrogenation, the direct addition of aldehydes was found to be an effective but simpler way of alcohol activation that can lead to efficient and green aldehyde-catalyzed transition metal-free dehydrative C-alkylation of methyl carbinols with alcohols. Mechanistic studies revealed that the reaction proceeds via in situ formation of ketones by Oppenauer oxidation of the methyl carbinols by external aldehydes, aldol condensation, and Meerwein–Ponndorf–Verley (MPV)-type reduction of α,β-unsatutated ketones by substrate alcohols, affording the useful long chain alcohols and generating aldehydes and ketones as the by-products that will be recovered in the next condensation to finish the catalytic cycle.
Co-reporter:Xiao-Chun Yu, Bo Li, Bao-Hua Yu, Qing Xu
Chinese Chemical Letters 2013 Volume 24(Issue 7) pp:605-608
Publication Date(Web):July 2013
DOI:10.1016/j.cclet.2013.04.011
Tetrabutylammonium fluoride (TBAF) effectively facilitated a denitrative substitution reaction of electron-deficient nitroarenes with phenylthiotrimethylsilane (PhSTMS) under mild and base-free neutral conditions at room temperature, providing a practical and efficient synthesis of useful unsymmetrical diaryl thioethers. Nitroarenes bearing ortho- and para-positioned electron-withdrawing groups are the most reactive substrates, indicating that this reaction most possibly proceeded via the nucleophilic aromatic substitution (SNAr) mechanism.Tetrabutylammonium fluoride (TBAF) effectively facilitated a denitrative substitution reaction of electron-deficient nitroarenes with phenylthiotrimethylsilane (PhSTMS) under mild and base-free neutral conditions at room temperature, providing a practical and efficient synthesis of the useful unsymmetrical diaryl thioethers. Nitroarenes bearing ortho- and para-positioned electron-withdrawing groups are the most reactive substrates, indicating that this reaction most possibly proceeded via the nucleophilic aromatic substitution (SNAr) mechanism.
Co-reporter:Bo Huang, Haiwen Tian, Shoushuai Lin, Meihua Xie, Xiaochun Yu, Qing Xu
Tetrahedron Letters 2013 Volume 54(Issue 22) pp:2861-2864
Publication Date(Web):29 May 2013
DOI:10.1016/j.tetlet.2013.03.098
By catalyst and condition screening, a simple Cu(I)/TEMPO-catalyst system was found to be an active and highly effective catalyst for the aerobic oxidation of amines to imines in open air at room temperature under neat conditions. This new method provided a mild, efficient, and practical alternative for the synthesis of the useful imines directly from primary and secondary amines.By catalyst and condition screening, a simple Cu(I)/TEMPO-catalyst system was found to be an active and highly effective catalyst for the aerobic oxidation of amines to imines in open air at room temperature under neat conditions. This new method provided a mild, efficient, and practical alternative for the synthesis of the useful imines directly from primary and secondary amines.Figure optionsDownload full-size imageDownload as PowerPoint slide
Co-reporter:Quan Liu;Zhongxiang Lu;Wenfei Ren;Kaibo Shen;Yu Wang
Chinese Journal of Chemistry 2013 Volume 31( Issue 6) pp:764-772
Publication Date(Web):
DOI:10.1002/cjoc.201300120
Abstract
By optimizing the reaction conditions via a careful screening of the bases and solvents, we developed an efficient transition metal-free method for CO cross-coupling of activated and unactivated heteroaryl chlorides with primary and secondary alcohols and phenols, providing a simple, efficient, and practical method for synthesis of the useful unsymmetrical heteroaryl alkyl and heteroaryl aryl ethers.
Co-reporter:Haiwen Tian;Xiaochun Yu;Qiang Li;Jianxin Wang
Advanced Synthesis & Catalysis 2012 Volume 354( Issue 14-15) pp:2671-2677
Publication Date(Web):
DOI:10.1002/adsc.201200574
Abstract
A general, green, and scalable synthesis of the useful imines and α,β-unsaturated imines is successfully achieved by a low-loading and powerful, mild and efficient copper-catalyzed aerobic oxidative reaction of alcohols and amines in the open air at room temperature under base- and dehydrating reagent-free conditions. This practical reaction can use air as the economic and green oxidant, tolerates a wide range of substrates, can afford high yields of the target imines on a large scale, and produces water as the only by-product, and thus being the best imination method as yet using alcohols and amines directly.
Co-reporter:Shiheng Liao, Kangkang Yu, Qiang Li, Haiwen Tian, Zhengping Zhang, Xiaochun Yu and Qing Xu
Organic & Biomolecular Chemistry 2012 vol. 10(Issue 15) pp:2973-2978
Publication Date(Web):20 Jan 2012
DOI:10.1039/C1OB06739G
By employing aerobic oxidation to aldehydes as a more effective alcohol activation strategy, ligand-free copper catalysts were found to be superior catalysts than other metals in aerobic dehydrative β-alkylation of secondary alcohols and α-alkylation of methyl ketones using alcohols as the green alkylating reagents. Based on our mechanistic studies and also supported by the literature, we deduce that the newly-proposed relay race process rather than the conventional borrowing hydrogen-type mechanisms should be the most possible and a more rational mechanism for the aerobic C-alkylation reactions.
Co-reporter:Qiang Li, Songjian Fan, Qing Sun, Haiwen Tian, Xiaochun Yu and Qing Xu
Organic & Biomolecular Chemistry 2012 vol. 10(Issue 15) pp:2966-2972
Publication Date(Web):20 Jan 2012
DOI:10.1039/C1OB06743E
By employing aerobic oxidation to aldehydes as a more effective alcohol activation strategy, we developed a green Cu-catalyzed N-alkylation method for various amides and amines with alcohols. This reaction is more advantageous than the literature methods for it uses a ligand-free copper catalyst, can be readily carried out under milder aerobic conditions and generates water as the only byproduct. More importantly, based on our mechanistic studies and also supported by the literature, rather than following the previously-proposed mechanisms, we deduce that the newly-proposed relay race process should be the most possible and a more rational mechanism for the reactions, especially under aerobic conditions.
Co-reporter:Xiaochun Yu;Lan Jiang;Qiang Li;Yuanyuan Xie
Chinese Journal of Chemistry 2012 Volume 30( Issue 10) pp:2322-2332
Publication Date(Web):
DOI:10.1002/cjoc.201200462
Abstract
Possibly because homogeneous palladium catalysts are not typical borrowing hydrogen catalysts and ligands are thus ineffective in catalyst activation under conventional anaerobic conditions, they had not been used in the N-alkylation reactions of amines/amides with alcohols in the past. By employing the aerobic relay race methodology with Pd-catalyzed aerobic alcohol oxidation being a more effective protocol for alcohol activation, ligand-free homogeneous palladiums are successfully used as active catalysts in the dehydrative N-alkylation reactions, giving high yields and selectivities of the alkylated amides and amines. Mechanistic studies implied that the reaction most probably proceeds via the novel relay race mechanism we recently discovered and proposed.
Co-reporter:Xiaochun Yu, Chuanzhi Liu, Lan Jiang, and Qing Xu
Organic Letters 2011 Volume 13(Issue 23) pp:6184-6187
Publication Date(Web):October 31, 2011
DOI:10.1021/ol202582c
By simply running the reactions under air and solvent-free conditions using catalytic amounts of manganese dioxide, a practical and efficient N-alkylation method for a variety of sulfonamides and amines using alcohols as green alkylating reagents was developed.
Co-reporter:Sun Lin Feng, Chuan Zhi Liu, Qiang Li, Xiao Chun Yu, Qing Xu
Chinese Chemical Letters 2011 Volume 22(Issue 9) pp:1021-1024
Publication Date(Web):September 2011
DOI:10.1016/j.cclet.2011.03.014
By using the famous Wilkinson's catalyst, N-alkylation of sulfonamides can be easily realized under mild aerobic conditions by using alcohols as the alkylating reagent, giving monoalkylated sulfonamides in high yields and selectivities with water produced as the only byproduct. This advantageous aerobic method is potentially general in substrate scope that it can also be applied to other amides, amines and alcohols.
Co-reporter:Chuanzhi Liu, Shiheng Liao, Qiang Li, Sunlin Feng, Qing Sun, Xiaochun Yu, and Qing Xu
The Journal of Organic Chemistry 2011 Volume 76(Issue 14) pp:5759-5773
Publication Date(Web):June 9, 2011
DOI:10.1021/jo200862p
The thermodynamically unfavorable anaerobic dehydrogenative alcohol activation to aldehydes and hydridometal species is found to be the bottleneck in metal-catalyzed N-alkylations due to a general and unnoticed catalyst deactivation by amines/amides. Thus, different from the anaerobic dehydrogenation process in borrowing hydrogen or hydrogen autotransfer reactions that require noble metal complexes or addition of capricious ligands for catalyst activation, the water-producing, exothermic, metal-catalyzed aerobic alcohol oxidation is thermodynamically more favorable and the most effective and advantageous aldehyde generation protocol. This leads to a general and advantageous air-promoted metal-catalyzed aerobic N-alkylation methodology that effectively uses many simpler, less expensive, more available, and ligand-free metal catalysts that were inactive under typical anaerobic borrowing hydrogen conditions, avoiding the use of preformed metal complexes and activating ligands and the exclusive requirement of inert atmosphere protection. This aerobic method is quite general in substrate scope and tolerates various amides, amines, and alcohols, revealing its potentially broad utilities and interests in academy and industry. In contrast to the commonly accepted borrowing hydrogen mechanism, based on a thorough mechanistic study and supported by the related literature background, a new mechanism analogous to the relay race game that has never been proposed in metal-catalyzed N-alkylation reactions is presented.
Co-reporter:Fang Wang, Lin Xu, Jiejun Huang, Shishi Wu, Lei Yu, Qing Xu, Yining Fan
Molecular Catalysis (May 2017) Volume 432() pp:99-103
Publication Date(Web):1 May 2017
DOI:10.1016/j.mcat.2017.02.010
•Isopropylation of acetone with isopropanol to produce MIBK as the neat result.•Iisopropanol as the safe hydrogen source instead of H2.•Solvent, by-product and catalyst all recyclable & reusable.•Green and practical procedures that generate no wastes.A stepwise isopropylation reaction of acetone is developed for preparation of methyl isobutyl ketone (MIBK) through acetone condensation and a recoverable Pt/C-catalyzed transfer hydrogenation of mesityl oxide (MO) with isopropanol (IPA). Almost quantitative MO conversion (up to 99.9%) and excellent MIBK selectivity (up to 99.3%) could be achieved by the method. Since IPA can be obtained from propane, a cheap petrochemical product, the by-product acetone (AT) generated in the reduction of MO could be easily recovered and reused in the preparation of MO, and the Pt/C catalyst could be recycled and reused, this H2- and waste-free reaction may be a green and practical method for preparation of the useful fine chemical MIBK.Download full-size image
Co-reporter:Qiang Li, Songjian Fan, Qing Sun, Haiwen Tian, Xiaochun Yu and Qing Xu
Organic & Biomolecular Chemistry 2012 - vol. 10(Issue 15) pp:NaN2972-2972
Publication Date(Web):2012/01/20
DOI:10.1039/C1OB06743E
By employing aerobic oxidation to aldehydes as a more effective alcohol activation strategy, we developed a green Cu-catalyzed N-alkylation method for various amides and amines with alcohols. This reaction is more advantageous than the literature methods for it uses a ligand-free copper catalyst, can be readily carried out under milder aerobic conditions and generates water as the only byproduct. More importantly, based on our mechanistic studies and also supported by the literature, rather than following the previously-proposed mechanisms, we deduce that the newly-proposed relay race process should be the most possible and a more rational mechanism for the reactions, especially under aerobic conditions.
Co-reporter:Shiheng Liao, Kangkang Yu, Qiang Li, Haiwen Tian, Zhengping Zhang, Xiaochun Yu and Qing Xu
Organic & Biomolecular Chemistry 2012 - vol. 10(Issue 15) pp:NaN2978-2978
Publication Date(Web):2012/01/20
DOI:10.1039/C1OB06739G
By employing aerobic oxidation to aldehydes as a more effective alcohol activation strategy, ligand-free copper catalysts were found to be superior catalysts than other metals in aerobic dehydrative β-alkylation of secondary alcohols and α-alkylation of methyl ketones using alcohols as the green alkylating reagents. Based on our mechanistic studies and also supported by the literature, we deduce that the newly-proposed relay race process rather than the conventional borrowing hydrogen-type mechanisms should be the most possible and a more rational mechanism for the aerobic C-alkylation reactions.
Co-reporter:Lei Yu, Mingxuan Liu, Fenglin Chen and Qing Xu
Organic & Biomolecular Chemistry 2015 - vol. 13(Issue 31) pp:NaN8392-8392
Publication Date(Web):2015/06/09
DOI:10.1039/C5OB00868A
The discovery of a series of novel organic reactions has made methylenecyclopropanes (MCPs) some of the most popular building blocks in synthetic organic chemistry during the past two decades. Among reported works, the construction of heterocycles from MCPs has highlighted new synthetic methodologies that afford more opportunities for the quick synthesis of elaborately substituted products, and this should draw a great deal of attention. However, reviews in this area are insufficient, and the latest monograph on heterocycle synthesis from MCPs was published 12 years ago. This review aims to summarize the novel organic reactions of MCPs to produce heterocycles published in recent years, which have provided specific and powerful tools for organic synthesis.