1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 z Catalysis Iron Catalyzed Cascade Protocol for the Synthesis of Pyrrolo[1, 2-a]quinoxalines: A Powerful Tool to Access Solid State Emissive Organic Luminophores Jatin J. Lade + , [a] Bhausaheb N. Patil + , [a] Pratima A. Sathe, [a] Kamlesh S. Vadagaonkar + , [b] Prabhakar Chetti, [c] and Atul C. Chaskar* [a] An alluring iron catalyzed cascade process has been developed for the synthesis of pyrrolo[1, 2-a]quinoxalines by using 1-(2- aminoaryl)pyrrole and arylacetic acids. This method involves oxidative decarboxylation of arylacetic acids into aromatic aldehydes followed by their condensation with 1-(2-aminoaryl) pyrrole. Optical properties of newly synthesized pyrrolo[1, 2-a] quinoxaline derivatives have been systematically investigated in solution as well as in solid state. Introduction Quinoxaline sits into a family of nitrogen containing hetero- cycles and shows very important biological activities. [1] Specifi- cally, functionalized pyrrolo[1,2-a]quinoxalines display a broad spectrum of biological activities such as anticancer, [2] anti- proliferative, [3] antimalarial, [4] anti-leishmanial, [5] and antitumor [6] etc. Quinoxaline derivatives have been used for amyloid fibril detection due to their excellent fluorescence properties. [7] In addition to this, they are also known to act as second generation non-nucleoside reverse transcriptase inhibitor (NNRTI) and VEGFR-3 kinase inhibitor. Moreover, they have been employed as a template for the synthesis of GABA benzodiazepine receptor agonist or antagonist. [8] Along with such ubiquitous biological activities, they are also found to be applicable in organic semiconductors, dyes, chemically controllable switches etc. [9,10] Due to such wide applicability of such compounds, development of novel methodologies for their synthesis is an attentive area of research for the synthetic chemists. [11] The inception for the synthesis of these compounds had been done by Cheeseman and Tuck groups in 1965. [12] Later on, various research groups have focused on developing novel methodologies for the synthesis of pyrrolo[1, 2-a]quinoxalines, but still one-pot cas- cade reaction for their synthesis is highly desirable. In 2011, Verma et al. modified Pictet-Spengler reaction for the tandem synthesis of pyrrolo[1, 2-a]quinoxalines by using lewis acid. [13] Pereira and Thiery used Iron in hydrochloric acid for the reduction of 1-(2-nitrophenyl)-1H-pyrrole followed by their condensation with aldehydes generated in situ by aerobic oxidation of alcohols to form pyrrolo[1, 2-a]quinoxalines. [14] Jayaprakash et al. [15] reported the synthesis of indolo- and pyrrolo[1, 2-a]quinoxalines by using a stoichiometric quantity of iodine, Zhai and co-workers [16] reported use of iodine as a catalyst and oxygen as an oxidant while Nath et al. [17] as well as Chen et al. [18] discovered Brønsted acid for the same. Recently, Zhai and co-workers [19] developed additive as well as catalyst free protocol whereas Jiang et al. [20] described metal-free aerobic oxidative synthesis of pyrrolo[1, 2-a]quinoxalines. However, these synthetic protocols won’t prove to be mild and simple because of harsh reaction conditions, stoichiometric quantity of catalysts, low yields etc. Hence, it is necessary to develop a synthetic strategy for easy access of such ubiquitous heterocycles. Organic luminophores have received enormous attention owing to their potential applications in optical devices, electronics and nano-biotechnology. [21–25] Moreover, they pos- sess some significant promising properties like high lumines- cence quantum efficiency, color purity, photostability and easy synthetic access. [26] Thus, synthesis of organic materials which exhibit high fluorescence efficiency in solid as well as solution state is highly desirable. In this context and continuation with our interest in developing novel, efficient and simple strategy for accessing various heterocyclic compounds, [27] we envisaged to access biologically as well as pharmaceutically important pyrrolo[1, 2- a]quinoxalines. Therefore, herein we report Iron catalyzed cascade reaction of 1-(2-aminoaryl)pyrrole and Arylacetic acids for the synthesis of pyrrolo[1, 2-a]quinoxalines (Scheme 1). Among the synthesized pyrrolo[1, 2-a]quinoxalines compounds 3m-3p showed excellent fluorescence properties (Figure 1). [a] J. J. Lade, + B. N. Patil, + P. A. Sathe, Dr. A. C. Chaskar National Centre for Nanosciences and Nanotechnology, University of Mumbai-400 098, India Tel: + 91-7507375261 E-mail: achaskar25@gmail.com [b] K. S. Vadagaonkar + Department of Dyestuff Technology, Institute of Chemical Technology, Mumbai-400019, India [c] Dr. P. Chetti Department of Chemistry, National Institute of Technology, Kurukshetra 136119, Haryana, India [ + ] Authors contributed equally to this work. The authors declare no competing financial interest. Supporting information for this article is available on the WWW under https://doi.org/10.1002/slct.201701383 Full Papers DOI: 10.1002/slct.201701383 6811 ChemistrySelect 2017, 2, 6811 – 6817  2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim