Iodine/Copper Iodide-Mediated C-H Functionalization: Synthesis of Imidazo[1,2-a]pyridines and Indoles from N-Aryl Enamines.

A practical intramolecular C-H functionalization reaction of N-aryl enamines has been carried out with molecular iodine (I2) as the sole oxidant in the presence of copper iodide (CuI). The efficient and versatile synthetic method described here is compatible with both N-heteroaryl and N-aryl substituted enamines and produces diverse imidazo[1,2-a]pyridine and indole derivatives via I2-mediated oxidative C-N and C-C bond formation, respectively. This ligand-free C-H functionalization methodology also works well with crude enamines, which allows for the sequential synthesis of the products directly from arylamines and ketones (or alkynes) without purification of the enamine intermediates.

[1]  Jie Dong,et al.  CBr4 Mediated Oxidative C-N Bond Formation: Applied in the Synthesis of Imidazo[1,2-α]pyridines and Imidazo[1,2-α]pyrimidines. , 2016, Organic letters.

[2]  Baohua Chen,et al.  Copper supported on H+-modified manganese oxide octahedral molecular sieves (Cu/H-OMS-2) as a heterogeneous biomimetic catalyst for the synthesis of imidazo[1,2-a]-N-heterocycles , 2016 .

[3]  C. Pan,et al.  Radical C-H functionalization to construct heterocyclic compounds. , 2016, Chemical communications.

[4]  P. Retailleau,et al.  Elements as Direct Feedstocks for Organic Synthesis: Fe/I2/O2 for Diamination of 2-Cyclohexenones with 2-Aminopyrimidine and 2-Aminopyridines. , 2015, Organic letters.

[5]  L. Dymińska.  Imidazopyridines as a source of biological activity and their pharmacological potentials-Infrared and Raman spectroscopic evidence of their content in pharmaceuticals and plant materials. , 2015, Bioorganic & medicinal chemistry.

[6]  A. Antonchick,et al.  Hypervalent Iodine(III) in Direct Carbon-Hydrogen Bond Functionalization , 2015 .

[7]  Junbiao Chang,et al.  Metal-free one-pot synthesis of 1,3-diazaheterocyclic compounds via I2-mediated oxidative C–N bond formation , 2015 .

[8]  K. R. Reddy,et al.  Copper-Catalyzed Oxidative C−H Amination: Synthesis of Imidazo[1,2-a]-N-Heterocycles from N-Heteroaryl Enaminones , 2015 .

[9]  Anil Kumar,et al.  Recent Developments in the Synthesis of Imidazo[1,2-a]pyridines , 2015 .

[10]  Zhengxing Wu,et al.  Copper-catalyzed C-H functionalization reactions: efficient synthesis of heterocycles. , 2015, Chemical reviews.

[11]  Jie Wu,et al.  Synthesis of 2-amino-1,3,4-oxadiazoles and 2-amino-1,3,4-thiadiazoles via sequential condensation and I2-mediated oxidative C–O/C–S bond formation. , 2015, The Journal of organic chemistry.

[12]  S. Santra,et al.  Synthesis of imidazo[1,2-a]pyridines: a decade update. , 2015, Chemical communications.

[13]  Anil Kumar,et al.  One-pot, three component tandem reaction of 2-aminopyridines, acetophenones and aldehydes: synthesis of 3-aroylimidazo[1,2-a]pyridines , 2015 .

[14]  Anil Kumar,et al.  Synthesis of 3-aroylimidazo[1,2-a]pyridines via CuCl2 catalyzed tandem dual carbon–nitrogen bonding , 2014 .

[15]  Jie Wu,et al.  I2-mediated oxidative C-N bond formation for metal-free one-pot synthesis of di-, tri-, and tetrasubstituted pyrazoles from α,β-unsaturated aldehydes/ketones and hydrazines. , 2014, The Journal of organic chemistry.

[16]  M. Brimble,et al.  C-H functionalization in the synthesis of amino acids and peptides. , 2014, Chemical reviews.

[17]  M. Bousmina,et al.  Functionalization of Imidazo[1,2‐a]pyridines by Means of Metal‐Catalyzed Cross‐Coupling Reactions , 2014 .

[18]  A. Majee,et al.  Copper(II)-Catalyzed Aerobic Oxidative Coupling between Chalcone and 2-Aminopyridine via CH Amination: An Expedient Synthesis of 3-Aroylimidazo[1,2-a]pyridines , 2014 .

[19]  Junbiao Chang,et al.  I2-mediated oxidative C-O bond formation for the synthesis of 1,3,4-oxadiazoles from aldehydes and hydrazides. , 2013, The Journal of organic chemistry.

[20]  M. Shiri,et al.  Indoles in multicomponent processes (MCPs). , 2012, Chemical reviews.

[21]  Wei Yu,et al.  TBAI-catalyzed oxidative coupling of aminopyridines with β-keto esters and 1,3-diones-synthesis of imidazo[1,2-a]pyridines. , 2011, Chemical communications.

[22]  Ji Young Kim,et al.  Recent advances in the transition metal-catalyzed twofold oxidative C-H bond activation strategy for C-C and C-N bond formation. , 2011, Chemical Society reviews.

[23]  Zhiping Li,et al.  I2-catalyzed indole formation via oxidative cyclization of N-aryl enamines. , 2011, Chemistry, an Asian journal.

[24]  G. Choudhary,et al.  Introduction of a clean and promising protocol for the synthesis of β-amino-acrylates and 1,4-benzoheterocycles: an emerging innovation , 2011 .

[25]  M. Hamann,et al.  Marine indole alkaloids: potential new drug leads for the control of depression and anxiety. , 2010, Chemical reviews.

[26]  Huanrong Li,et al.  Iodine-mediated synthesis of 3H-indoles via intramolecular cyclization of enamines. , 2010, The Journal of organic chemistry.

[27]  G. Fabrizi,et al.  Copper-catalyzed C-C bond formation through C-H functionalization: synthesis of multisubstituted indoles from N-aryl enaminones. , 2009, Angewandte Chemie.

[28]  N. Jiao,et al.  Indoles from simple anilines and alkynes: palladium-catalyzed C-H activation using dioxygen as the oxidant. , 2009, Angewandte Chemie.

[29]  Yunfei Du,et al.  PIDA-mediated oxidative C-C bond formation: novel synthesis of indoles from N-aryl enamines. , 2009, Organic letters.

[30]  F. Glorius,et al.  Palladium-catalyzed oxidative cyclization of N-aryl enamines: from anilines to indoles. , 2008, Angewandte Chemie.

[31]  A. Gueiffier,et al.  Recent progress in the pharmacology of imidazo[1,2-a]pyridines. , 2007, Mini reviews in medicinal chemistry.

[32]  Jeffrey T. Kuethe,et al.  Practical methodologies for the synthesis of indoles. , 2006, Chemical reviews.

[33]  G. Fabrizi,et al.  Synthesis and functionalization of indoles through palladium-catalyzed reactions. , 2005, Chemical reviews.

[34]  F. Pinguet,et al.  REACTIVITY OF 6,7,8,9-TETRAHYDROPYRIDO[1,2-a]BENZIMIDAZOL-9-ONE : SYNTHESIS OF PYRROLOPYRIDOBENZIMIDAZOLES , 2001 .

[35]  J. Teulade,et al.  Heterocyclic enaminones: Photochemical synthesis of 6,7,8,9-tetrahydro-5H-pyrido[2,3-b]indol-9-ones , 1999 .

[36]  J. Bourguignon,et al.  A NOVEL METHOD OF PREPARATION OF 3-ACYLIMIDAZO1,2-ALPHA PYRIDINES , 1997 .