- Metal-free synthesis of aminomethylated imidazoheterocycles: dual role of tert-butyl hydroperoxide as both an oxidant and a methylene source
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A novel and efficient aminomethylation approach has been developed for the regioselective functionalization of imidazoheterocycles under metal-free conditions. A wide range of imidazoheterocycles and 2/4-aminoazaheterocycles successfully provided corresponding aminomethylated imidazoheterocycles in moderate to excellent (33-80%) yields. The isotopic labelling study suggested that TBHP played a dual role as both an oxidant and a methylene source in this transformation. The developed protocol follows a radical pathway which is supported by radical trapping experiments.
- Patel, Om P. S.,Nandwana, Nitesh Kumar,Sah, Ajay Kumar,Kumar, Anil
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- One-Pot Synthesis of 3-Methyl-2-arylimidazo[1,2-a]pyridines Using Calcium Carbide as an Alkyne Source
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An efficient method for the construction of 3-methyl-2-arylimidazo[1,2-a]pyridines from the reactions of calcium carbide, 2-aminopyridines, and aromatic aldehydes is described. The notable advantages for this strategy include the use of an inexpensive and
- Chen, Wei,Li, Zheng
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- CuCl2-catalyzed N[sbnd]O bond cleavage of oxime esters: Approach to imidazoheterocycles and furo[3,2-c]chromenyl fused imidazoles
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An articulate approach to a diverse set of imidazoheterocycles in good to high yields via a copper-catalyzed aza-annulation of several oxime esters with a group of 2-amino-azaarenes was developed. The above cyclization reaction probably proceeds via a single electron transfer process which embodies a new technique for creating two new C[sbnd]N bonds for imidazole ring synthesis. Gratifyingly, the implementation of this chemistry could be further stretched to the synthesis of a novel class of fused imidazoles bearing a furo[3,2-c]chromene moiety via a sequential C[sbnd]N bond formation, followed by C(sp2)-H functionalization/5-endo-dig-oxacyclization (C[sbnd]C and C[sbnd]O bonds) of in situ produced fused imidazoles with cyclic enynones in the presence of copper(II) as a π-electrophilic Lewis acid catalyst.
- Gudimella, Santosh K.,Kaur, Amanpreet,Kumar, Ram,Samanta, Sampak
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supporting information
(2020/07/08)
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- Visible-light-promoted sulfonylmethylation of imidazopyridines
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The visible light promoted C–H sulfonylmethylation of imidazopyridines with easily accessible bromomethyl sulfones under mild reaction conditions was described. This protocol provides an effective and practical access to sulfonylmethylated imidazopyridines with good functional group tolerance. The desired products were provided in moderate to excellent yields for 50 examples at room temperature. The method could also be an attractive strategy to install a methyl group on imidazopyridines.
- Mi, Xia,Kong, Yuanfang,Zhang, Jingyu,Pi, Chao,Cui, Xiuling
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supporting information
p. 2295 - 2298
(2019/10/28)
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- Metal-free, base catalyzed oxidative amination and denitration reaction: Regioselective synthesis of 3-arylimidazo[1,2-a]pyridines
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A metal-free, regioselective strategy for the synthesis of 3-arylimidazo[1,2-a]pyridines from β-nitrostyrenes and 2-aminopyridines using triethylamine as the catalyst and H2O2 (30% aq.) as the oxidant is reported. The use of an inexp
- Devi, Elango Sankari,Alanthadka, Anitha,Nagarajan, Subbiah,Sridharan, Vellaisamy,Maheswari, Chockalingam Uma
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supporting information
p. 3485 - 3489
(2018/08/22)
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- Regiocontrolled functionalization of 2,3-dihalogenoimidazo[1,2-a]pyridines by Suzuki-Miyaura and Sonogashira cross-coupling reactions
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An efficient method for regiocontrolled functionalization of 2,3-dihalogenoimidazo[1,2-a]pyridine was developed. This sequence allowed the selective introduction of aryl, heteroaryl, alkyl and alkynyl substituents at both 2- and 3-positions, by using Suzu
- Delaye,Pénichon,Allouchi,Enguehard-Gueiffier,Gueiffier
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p. 4199 - 4203
(2017/07/10)
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- Au-catalyzed domino process synthesis of imidazo[1,2-a]pyridines from 2-aminopyridine and N-tosylhydrazones: An efficient C[sbnd]N bond formation reaction
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A novel Au-catalyzed domino reaction for the synthesis of imidazo[1,2-a]pyridines from 2-aminopyridine and N-tosylhydrazones has been developed using molecular oxygen. It represents a new strategy for the formation of C[sbnd]N bonds. This transformation demonstrated a broad tolerance toward the substrates and allowed the generation of a diverse imidazo[1,2-a]pyridine derivatives with good yields.
- Guo, Pengfeng,Huang, Shuyu,Mo, Jiaxian,Chen, Xiaoyan,Jiang, Hangqi,Chen, Weifeng,Cai, Hehuan,Zhan, Haiying
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- Copper-Catalyzed Aerobic Oxidative Cyclization of Ketoxime Acetates with Pyridines for the Synthesis of Imidazo[1,2-a]pyridines
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A copper(I)-catalyzed aerobic oxidative coupling of ketoxime acetates with simple pyridines for the synthesis of imidazo[1,2-a]pyridines has been developed. This reaction tolerates a wide range of functional groups and it affords a series of valuable imidazo[1,2-a]pyridines in high yields under mild conditions.
- Ren, Zhi-Hui,Zhao, Mi-Na,Yi, Yukun,Wang, Yao-Yu,Guan, Zheng-Hui
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p. 1920 - 1926
(2016/06/15)
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- Transition-Metal-Free Tandem Chlorocyclization of Amines with Carboxylic Acids: Access to Chloroimidazo[1,2-α]pyridines
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An efficient one-pot and transition-metal-free chlorocyclization cascade of 2-aminopyridines with aliphatic carboxylic acids is reported. This transformation provides a novel approach to 2-chloro- or 3-chloro-substituted imidazo[1, 2-α]pyridines with a br
- Xiao, Xinsheng,Xie, Ying,Bai, Siyi,Deng, Yuanfu,Jiang, Huanfeng,Zeng, Wei
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supporting information
p. 3998 - 4001
(2015/09/01)
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- Highly efficient and eco-friendly protocol to functionalized imidazoles via ring-opening of α-nitro epoxides
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A simple and direct synthesis of functionalized imidazoles from α-nitro-epoxides and amidines was developed. This reaction could proceed smoothly in a highly efficient and eco-friendly manner in moderate to excellent yields. A plausible mechanism has also
- Guo, Xiao,Shao, Jiaan,Liu, Huan,Chen, Binhui,Chen, Wenteng,Yu, Yongping
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p. 51559 - 51562
(2015/06/25)
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- Heterogeneously copper-catalyzed oxidative synthesis of imidazo[1,2-a]pyridines using 2-aminopyridines and ketones under ligand- and additive-free conditions
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An efficient and mild heterogeneously CuCl2/nano-TiO 2-catalyzed aerobic synthesis of imidazo[1,2-a]pyridines from 2-aminopyridines and ketones has been developed using air as the oxidant in the absence of any ligands and additives. This strategy was compatible with a large range of substrates, including unactivated aryl ketones and unsaturated ketones and went through the C-H bond functionalization mechanism instead of I --assisted Ortoleva-King reaction to provide the corresponding imidazo[1,2-a]pyridines in good yields with low catalyst loading (0.8 mol%). Moreover, the heterogeneous catalyst can be successfully employed in gram-scale synthesis and reused many times without the significant loss of catalytic activity.
- Meng, Xu,Wang, Yanmin,Yu, Chaoying,Zhao, Peiqing
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p. 27301 - 27307
(2014/07/21)
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- Iron(III)-catalyzed three-component domino strategy for the synthesis of imidazo[1,2-a]pyridines
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An efficient, one-pot, three-component domino strategy has been demonstrated for the synthesis of imidazo[1,2-a]pyridines using a catalytic amount of Fe(III) chloride in high yields in air. A library of imidazo[1,2-a]pyridines was synthesized by the reaction of easily available aldehydes and 2-aminopyridines in a mixture of nitroalkane and DMF (2:1). This transformation presumably occurs by a sequential aza-Henry reaction/cyclization/denitration. The use of readily available chemicals as starting materials, inexpensive metal catalyst, aerobic reaction conditions, tolerance of a wide range of functional groups, and operational simplicity are the notable advantages of this present protocol.
- Santra, Sougata,Mitra, Shubhanjan,Bagdi, Avik Kumar,Majee, Adinath,Hajra, Alakananda
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supporting information
p. 5151 - 5155
(2014/12/10)
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- Iron(III)-catalyzed denitration reaction: One-pot three-component synthesis of imidazo[1,2-a]pyridine derivatives
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An iron(III)-catalyzed one-pot three-component cross-coupling nitration reaction of 2-aminopyridines, aldehydes and nitroalkanes, straightforwardly forms imidazo[1,2-a]pyridine derivatives and is described in this report. The system shows good functional-group tolerance and proceeds smoothly in moderate to good yields. An iron(III)-catalyzed one-pot three-component cross-coupling nitration reaction of 2-aminopyridines, aldehydes, and nitroalkane, leading to the straightforward formation of imidazo[1,2-a]pyridine derivatives has been reported. In this procedure, the starting materials are commercially available. The system shows good functional-group tolerance and proceeds smoothly in moderate to good yields. Copyright
- Yan, Hao,Wang, Yuling,Pan, Congming,Zhang, Hao,Yang, Sizhuo,Ren, Xiaoyu,Li, Jian,Huang, Guosheng
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p. 2754 - 2763
(2014/05/06)
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- Aerobic multicomponent tandem synthesis of 3-sulfenylimidazo[1,2-a] pyridines from ketones, 2-aminopyridines, and disulfides
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An aerobic CeCl3·7H2O/NaI-catalyzed C-H functionalization reaction was developed for the synthesis of 3-sulfenylimidazo[1,2-a]pyridines from easily available ketones, 2-aminopyridines, and disulfides without DMSO or peroxide as an ox
- Ge, Wenlei,Zhu, Xun,Wei, Yunyang
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supporting information
p. 6015 - 6020
(2013/09/24)
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- CuI-catalyzed aerobic oxidative α-aminaton cyclization of ketones to access aryl or alkenyl-substituted imidazoheterocycles
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CuI-catalyzed aerobic oxidative synthesis of imidazoheterocycles has been achieved. Four hydrogen atoms were removed in one step. This protocol was compatible with a broad range of functional groups, and it has been also successfully extended to unsaturated ketones, bringing about the formation of alkenyl-substituted imidazoheterocycles, which were difficult to prepare by previous means. Preliminary mechanistic studies indicated that this reaction was most likely to proceed through a catalytic Ortoleva-King reaction. By using this method, the marketed drug Zolimidine could be prepared with 90% yield on a gram scale from commercially available materials.
- Zhang, Yuhong,Zhang, Yuanfei,Chen, Zhengkai,Wu, Wenliang,Su, Weiping
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supporting information
p. 12494 - 12504
(2014/01/17)
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- Conversion of pyridine to imidazo[1,2-a]pyridines by copper-catalyzed aerobic dehydrogenative cyclization with oxime esters
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A rapid and environmentally friendly conversion of pyridine to imidazo[1,2-a]pyridines has been developed via copper-catalyzed aerobic dehydrogenative cyclization with ketone oxime esters.
- Huang, Huawen,Ji, Xiaochen,Tang, Xiaodong,Zhang, Min,Li, Xianwei,Jiang, Huanfeng
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supporting information
p. 6254 - 6257
(2014/01/17)
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- One-pot synthesis of 2-phenylimidazo[1,2-α]pyridines from acetophenone, [Bmim]Br3 and 2-aminopyridine under solvent-free conditions
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One-pot synthesis of 2-phenylimidazo[1,2-α]pyridines from acetophenone, [Bmim]Br3 and 2-aminopyridine under solvent-free conditions in the presence of Na2CO3, gave the corresponding 2-phenylimidazo[1,2-α]pyridines in excel
- Le, Zhang-Gao,Xie, Zong-Bo,Xu, Jian-Ping
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p. 13368 - 13375
(2013/02/22)
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- Iron(II)-catalyzed denitration reaction: Synthesis of 3-methyl-2- arylimidazo[1,2-a]pyridine derivatives from aminopyridines and 2-methylnitroolefins
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A variety of ways to synthesize imidazo[1,2-a]pyridines have been reported and many approaches are devoted to the functionalization of imidazo[1,2-a] pyridines. However, the use of a denitration reaction in the synthesis of imidazo[1,2-a]pyridines has not
- Yan, Hao,Yang, Sizhuo,Gao, Xiai,Zhou, Kang,Ma, Chao,Yan, Rulong,Huang, Guosheng
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supporting information
p. 2961 - 2964
(2013/02/22)
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- Copper-catalyzed decarboxylative three-component reactions for the synthesis of imidazo[1,2-a]pyridines
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Imidazo[1,2-a]pyridine derivatives were synthesized through multicomponent coupling reactions of 2-aminopyridines, aldehydes, and alkynecarboxylic acids in the presence of 10 mol-% CuI/Cu(OTf)2. Both aryl- and alkyl-substituted alkynecarboxylic acids, including propiolic acid, were good alkyne sources and afforded the desired imidazo[1,2-a]pyridines in good yields through the decarboxylative coupling reactions. Arylalkynecarboxylic acids were synthesized through palladium-catalyzed coupling reactions between aryl iodides and propiolic acid and reacted with 2-aminopyridine and aldehydes, with or without a purification step. In both cases the desired imidazo[1,2-a]pyridines were obtained in good yields. Mechanistic studies suggested that in the case of propiolic acid the decarboxylative addition predominates over terminal alkyne addition. Imidazo[1,2-a]pyridine derivatives were synthesized through three-component coupling reactions of 2-aminopyridines, aldehydes, and alkynecarboxylic acids in the presence of 10 mol-% CuI/Cu(OTf)2 Copyright
- Palani, Thiruvengadam,Park, Kyungho,Kumar, Manian Rajesh,Jung, Hyun Ming,Lee, Sunwoo
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supporting information
p. 5038 - 5047
(2012/11/07)
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- Iodobenzene-catalyzed synthesis of imidazo[1,2-a]pyridines from aryl ketones with mCPBA in ionic liquid
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Iodobenzene-catalyzed synthesis of imidazo[1,2-a]pyridines from aryl ketones with mCPBA as a cooxidant in ionic liquid is described. The method is simple, rapid and practical, generating Imidazo[1,2-a]pyridines from the aryl ketone without isolation of α-
- Chang, Ya-Li,Wang, Huey-Min,Hou, Rei-Sheu,Kang, Iou-Jiun,Chen, Ling-Ching
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experimental part
p. 153 - 156
(2011/04/16)
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- Microwave-assisted, one-pot reaction of pyridines, -bromoketones and ammonium acetate: An efficient and simple synthesis of Imidazo[1,2- a ]-pyridines
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A novel and efficient synthesis of imidazo[1,2-a]pyridines is described. N-Phenacylpyridinium bromides, which were prepared in situ from the addition of pyridines to -bromoketones, undergo nucleophilic addition of ammonium acetate under microwave irradiation and solvent-free conditions to afford the corresponding imidazo[1,2-a]pyridines in excellent yields.
- Adib, Mehdi,Mohamadi, Ali,Sheikhi, Ehsan,Ansari, Samira,Bijanzadeh, Hamid Reza
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experimental part
p. 1606 - 1608
(2010/08/20)
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- Liquid-phase organic synthesis of imidazo[1,2-a]pyridine derivatives using PEG-supported sulfonyl chloride
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Reaction of PEG-bound sulfonic acid with thionyl chloride formed the difunctionalised PEG-supported sulfonyl chloride, which was treated with α-hydroxyketones, followed by treatment with 2-aminopyridine in the presence of potassium carbonate efficient to afford imidazo[1,2-a]pyridines in good yields with a facile work-up procedure.
- Wang, Chao-Li,Sheng, Shou-Ri.,Chen, Hu,Liu, Xiao-Ling,Cai, Ming-Zhong
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experimental part
p. 289 - 291
(2009/04/16)
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- Titanium(IV) chloride promoted syntheses of new imidazo[1,2-a]pyridine derivatives under microwave conditions
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A new method is described for the synthesis of imidazo[1,2-a]pyridine derivatives from the reaction of 2-aminopyridines with α-haloketones. The critical reagent is titanium(IV) chloride, which appears to serve as a strong dehydrating agent to promote formation of putative Schiff base intermediates, which cyclize subsequently to form the products. The reactions were performed rapidly under microwave conditions. Multiple reaction conditions were evaluated, including reaction temperature, solvent and other Lewis acids. Various combinations of substitution patterns in both the α-haloketone and 2-aminopyridine substrates were examined to evaluate the scope of the reaction. The reaction is quite sensitive to substituents in both substrates, especially those with basicity or coordination ability. Georg Thieme Verlag Stuttgart.
- Cai, Lisheng,Brouwer, Chad,Sinclair, Kathryn,Cuevas, Jessica,Pike, Victor W.
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p. 133 - 145
(2007/10/03)
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- Hypervalent iodine(III) sulfonate mediated synthesis of imidazo[1,2-a]pyridines
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A direct and efficient method for the conversion of alkyl aryl ketones to imidazo[1,2-a]pyridines has been developed based on initial formation of α-organosulfonyloxy ketones and their subsequent cyclocondensation by 2-aminopyridines in one-pot conditions
- Huang, Hsin-Yu,Hou, Rei-Sheu,Wang, Huey-Min,Chen, Ling-Ching
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p. 1377 - 1380
(2007/10/03)
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- Organic reactions in ionic liquids: Ionic liquid-accelerated cyclocondensation of α-tosyloxyketones with 2-aminopyridine
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The room temperature ionic liquid n-butylpyridinium tetrafluoroborate (BPyBF4) is used as a 'green' recyclable alternative to classical molecular solvents for the cyclocondensation of α-tosyloxyketones with 2-aminopyridine. Significant rate enh
- Xie, Yuan-Yuan,Chen, Zhen-Chu,Zheng, Qin-Guo
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p. 1505 - 1508
(2007/10/03)
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- Reactivity of 3-iodoimidazo[1,2-a]pyridines using a Suzuki-type cross-coupling reaction
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The influence of base and solvent in Suzuki cross-coupling reaction on various 2-substituted-3-iodoimidazo[1,2-a]pyridines was reported. The reactivity was largely influenced by nature of the substituent. Optimized yields and shortened times of reaction were obtained using strong bases in DME.
- Enguehard, Cecile,Renou, Jean-Louis,Collot, Valerie,Hervet, Maud,Rault, Sylvain,Gueiffier, Alain
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p. 6572 - 6575
(2007/10/03)
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