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Ammonium Chloride–Catalyzed One-Pot Synthesis of Tetrahydrobenzo[α]xanthen-11one Derivatives Under Solvent-Free Conditions Naser Foroughifar
a b
a
a
, Akbar Mobinikhaledi , Hassan Moghanian ,
a
Reza Mozafari & Hamid R. M. Esfahani
b
a
Department of Chemistry, Faculty of Science, Arak University, Arak, Iran b
Faculty of Chemistry, Islamic Azad University, Tehran, Iran
Available online: 29 Jun 2011
To cite this article: Naser Foroughifar, Akbar Mobinikhaledi, Hassan Moghanian, Reza Mozafari & Hamid R. M. Esfahani (2011): Ammonium Chloride–Catalyzed One-Pot Synthesis of Tetrahydrobenzo[α]xanthen-11-one Derivatives Under Solvent-Free Conditions, Synthetic Communications, 41:18, 2663-2673 To link to this article: http://dx.doi.org/10.1080/00397911.2010.515340
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Synthetic Communications1, 41: 2663–2673, 2011 Copyright # Taylor & Francis Group, LLC ISSN: 0039-7911 print=1532-2432 online DOI: 10.1080/00397911.2010.515340
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AMMONIUM CHLORIDE–CATALYZED ONE-POT SYNTHESIS OF TETRAHYDROBENZO[a]XANTHEN11-ONE DERIVATIVES UNDER SOLVENT-FREE CONDITIONS Naser Foroughifar,1,2 Akbar Mobinikhaledi,1 Hassan Moghanian,1 Reza Mozafari,1 and Hamid R. M. Esfahani2 1
Department of Chemistry, Faculty of Science, Arak University, Arak, Iran Faculty of Chemistry, Islamic Azad University, Tehran, Iran
2
GRAPHICAL ABSTRACT
Abstract A one-pot, multicomponent reaction of aldehydes, dimedone, and b-naphthols is described for the preparation of 12-aryl- or 12-alkyl-8,9,10,12-tetrahydrobenzo[a]xanthen11-one derivatives using ammonium chloride as a mild, inexpensive, and environmentally benign catalyst under solvent-free conditions. Different types of aldehyde and b-naphthol derivatives are used in the reaction, and in all cases the products were synthesized successfully. Keywords Ammonium chloride; multicomponent; one pot; solvent-free; xanthene
INTRODUCTION Multicomponent reactions (MCRs), with three or more reactants combining in a one-pot procedure to give a single product, are a promising and vital field of chemistry because the synthesis of complicated molecules can be achieved in a very fast, efficient, and time-saving manner without the isolation of any intermediate.[1–4] As a result, it requires minimum effort, which minimizes the environmental loading and is acceptable from a ‘‘green chemistry’’ point of view. There has been tremendous development in three- or four-component reactions, especially Biginelli,[5,6] Passerini,[7] Ugi,[8,9] and Mannich[10,11] reactions, which have further led to a renaissance of MCRs. Nevertheless, great efforts still are being made to find and develop new MCRs. Received March 28, 2010. Address correspondence to Naser Foroughifar, Department of Chemistry, Faculty of Science, Arak University, Arak 38156-879, Iran. E-mail:
[email protected]
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N. FOROUGHIFAR ET AL.
The synthesis of xanthenes and benzoxanthenes has gained considerable attention in organic synthesis because of their wide range of therapeutic and biological properties, such as use as anti-inflammatory agents[12] and in photodynamic therapy.[13] Xanthene-based compounds have also been investigated for agricultural bactericide activity, and some other benzoxanthenes find applications in industries such as dyes in laser technology[14,15] and fluorescent materials for visualization of biomolecules.[16,17] Xanthene dyes are extracted naturally from soil and plants such as Indigofera longeracemosa.[18] Various methods are available for the construction of xanthenes and benzoxanthenes involving trapping of benzynes by phenols,[19] cyclocondensation reaction between 2-hydroxyaromatic aldehydes and 2-tetralone,[20] the reaction of aldehydes with 2-naphthol,[21,22] and intramolecular phenyl carbonyl coupling reactions of benzaldehydes and acetophenones.[23] Also, the synthesis of tetrahydrobenzo[a]xanthen-11-ones has been reported from condensation reaction of aldehydes, b-naphthol, and cyclic 1,3-dicarbonyl compounds in the presence of different catalysts such as NaHSO4 SiO2,[24] Sr(OTf)2,[25] para-toluenesulfonic acid (p-TSA),[26] ceric ammonium nitrate (CAN),[27] InCl3,[28] H3PW12O40,[29] and sulfamic acid.[30] However, these methodologies suffer from one or more disadvantages such as prolonged reaction time, toxic solvents, special reagents, and often expensive catalysts. Thus, the need for the development of an alternative route to construct the tetrahydrobenzo[a]xanthen-11-one derivatives is in high demand. RESULTS AND DISCUSSION During the course of our recent studies directed toward the development of practical, safe, and environmentally friendly procedures for some important transformations,[31–35] we succeeded in preparing tetrahydrobenzo[a]xanthen-11-one derivatives from condensation of aldehydes, dimedone, and b-naphthols in the presence of ammonium chloride in good to excellent yield without any other by-products (Scheme 1). For the primary study and optimization of reaction conditions, first we chose benzaldehyde and b-naphthol as a simple model for the reaction with dimedone in the presence of ammonium chloride. After many examinations, we found that the best conditions for this reaction were solvent-free with 10 mol% ammonium chloride at 120 C (Table 1). A slight excess of the dimedone was found to be advantageous, and hence the molar ratio of b-naphthol to dimedone was kept as 1:1.1. To explore the generality of the reaction, we extended our study using ammonium chloride as catalysts under solvent-free conditions with different aromatic
Scheme 1. Synthesis of tetrahydrobenzo[a]xanthene-11-one derivatives.
TETRAHYDROBENZO[a]XANTHEN-11-ONES
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Table 1. Optimization of reaction conditions Entry 1 2 3 4 5 6 7 8
Solvent
Ammonium chloride (mol%)
Temperature
Time (min)
Yield (%)a
CH2Cl2 C2H5OH THF CH3CN Toluene Solvent-free Solvent-free Solvent-free
10 10 10 10 10 10 10 20
Reflux Reflux Reflux Reflux Reflux Rt 120 C 120 C
120 120 120 120 120 120 15 15
41 63 70 30 40
