New Route for the Tetraphenylfuran Synthesis Using a Superacid Sulfonic Clay (SASC) as Catalyst
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New Route for the Tetraphenylfuran Synthesis Using a Superacid Sulfonic Clay (SASC) as Catalyst Carlos Damián Cea1, Eloy Vázquez Labastida2, Manuel Salmon S 1, Sergio O. Flores Valle
3
1
Instituto de Química, Universidad Nacional Autónoma de México. Circuito Exterior, Ciudad Universitaria, Coyoacán, México. D.F. 04510 2 Departamento de Química Orgánica y Polímeros, ESIQIE-IPN, Zacatenco, México, D. F. 07738 3 Laboratorio de Catálisis y Materiales, ESIQIE-IPN, Zacatenco, México, D. F. 07738 Corresponding author:Email: [email protected]
ABSTRACT The transformation of benzoin to tetraphenylfuran catalyzed with a superacid sulfonic clay under different reaction conditions was investigated. Three products with different yields were produced under a nitrogen stream and four products were obtained under an air atmosphere. Keywords: Catalyst, superacid sulfonic clay, tetraphenylfuran
INTRODUCTION Montmorillonites are a special group of clays characterized by their layered structure and their Brönsted and Lewis acid sites. They have been essentially employed as solid acids in a variety of methodologies [-6]. Big neutralization laundries are avoided when such superacids are used to replace H2SO4 and p-toluensulfonic acid. It has been reported that tetraphenylfuran could be obtained by using concentrated sulfuric acid in an aqueous solution of benzoin [7], which is an electron-rich compound widely used as test compound in (photo) oxidation experiments [8]. This procedure was modified by replacing the sulfuric acid with p-toluensulfonic acid in dry toluene [9]. Other procedures involving in the use of trialkyl phosphites on 2-ene-1,4-diones were also reported [10], their disadvantage is that it requires 1,2-dibenzoylstilbene which is not of easy acquisition. However, the goal product yield is low (10-42%) and by-products are obtained with moderate yields (150%, approximately). Tetraphenylfuran was synthesized by Dams [11] et al. leaving of benzoyl chloride in a procedure consisting of three steps, using species of low valence titanium; the tetraphenylfuran yield is as high as 80 %; however, one has to generate those compounds for using LiAlH4 on TiCl3. In 1999, Vazquez [6] et al. reported the preparation, characterization and evaluation of a superacid sulfonic clay (SASC). In the present work, we employed this kind of super acid solid as catalyst in the study of benzoin transformation. We report herein the synthesis of tetraphenylfuran with a single step procedure and the variation in the product yields under
various reaction conditions. Figure 1 describes the reaction pathways in the tetraphenylfuran synthesis.
O
O
O SASC
+
C6H6
O
OH
III
I II
O
O
+ (E)
O
+ O
O H
IV V
Figure 1. Transformation route of benzoin using a superacid sulfonic clay
EXPERIMENTAL Reaction 1 Benzoin (I) (2.0015 g, 0.0094 mol) and SASC (250 mg) were refluxed in dry benzene (20 mL) for 24 hours. The reaction advance was determined by Thin Layer Chromatography (TLC): Catalyst was removed by filtration in vacuum. The reaction mixture wa
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