Al(H2PO4)3: An Efficient and Effective Solid Acid Catalyst for Transesterification of β-keto Esters Under Solvent Free Condition

Abstract

Al(H 2 PO 4 ) 3 is an efficient, cheap and reusable heterogeneous catalyst for transesterification of b-ketoesters with a variety of alcohols in moderate to good yields within a short reaction time under solvent free condition.Keywords b-keto esters Á Alcohols Á Transesterification Á Solid catalyst Á Catalytic synthetic protocolThe transesterification of b-keto esters is an important transformation in organic synthesis as they are precursors of many important chemical intermediates, agrochemicals, polymer as well as in pharmaceutical industries [1]. The transesterification strategy is also employed for preparing optically active compounds from b-ketoesters by reaction with chiral alcohols [2]. Conventionally, dimethylamino pyridine (DMAP) is used as a choice of reagent for transesterification of b-keto esters in good yields, but it suffers from the limitations such as toxicity, high price and requirement of large amount of catalyst [3]. Over the years several catalysts like distannoxane [4], triphenyl phosphine [5], zeolites [6], kaolinitic clay [7], Zn/I 2 [8], ceria-yttria based Lewis acid catalyst [9], Nb 2 O 5 [10], 3-nitrobenzeneboronic acid [11] have been reported to accelerate the rate of transesterification of b-keto esters. Similarly some other heterogeneous catalysts such as S-SnO 2 [12], Amberlyst-15 [13], Envirocat EPZF R [14], montmorillonite K-10 [15], B 2 O 3 /ZrO 2 [16] are also effective for the transesterification of b-ketoesters. Nevertheless, there is still an ample scope to search for an effective catalyst for transesterification as most of the methods suffer from drawbacks such as longer reaction time, tedious work-up procedure, harsh reaction conditions and expensive reagents.Recently, there has been a considerable interest to develop catalysts for organic reactions by supporting inorganic reagents on inorganic materials having high surface area [17]. The nature of support has an important role in the catalytic activity mainly due to the intimate contact between the supported ions and the support surface. Moreover, the mechanical stability, ease of separation of catalyst from the reaction mixture and reusability are the added advantages of these solid catalysts.We wish to report herein the transesterification of b-ketoesters with a wide range of alcohols by using 5 mol% of solid acid catalyst Al(H 2 PO 4 ) 3 under solvent free condition within a very short reaction time (Scheme 1).Al(H 2 PO 4 ) 3 is a solid acid catalyst which is easy to prepare, stable, easily separable from the reaction mixture and recyclable which was prepared by literature procedure [18]. For optimization, the reaction of methyl acetoacetate with benzyl alcohol was carried out at various conditions and the results are summarized in Table 1. A blank reaction of methyl acetoacetate (5 mmol) and benzyl alcohol (5.5 mol) without using the catalyst was carried out which gave only 15% of the desired b-keto ester even after stirring for 24 h at room temperature. The same reaction in presence of Al(H 2 PO 4 ) 3 (0.5 mol%) at ro...

Synthesis Method for Thiosulfonate and Report of Its Insecticidal Activity in Anagasta kuehniella (Lepidoptera: Pyralidae)

“…The reaction of AgNO 3 with BF 3 ·OEt 2 in acetonitrile and in a nitrogen atmosphere at room temperature resulted in yields of 72%–75%. Employing the reaction with Al(H 2 PO 4 ) 3 , the solid acid [21] with concentrated nitric acid at room temperature resulted in yields of 56%–61%. The use of this reagent provides the possibility of the catalytic oxidative coupling of thiols under mild conditions.…”

Efficient carbonyl hydrosilylation reaction: Toward EVA copolymer crosslinking

“…Hydrosilylation reaction of unsaturated molecules have been largely developed with various catalytic systems 1, 2. Particularly, studies on the hydrosilylation reaction of carbonyl groups from ketone and aldehyde are well illustrated in the literature 3–7. It was reported that the yield of the hydrosilylation reactions depends mainly on the catalyst nature such as UV light,8 metal halides, NiCl 2 ,9 ZnCl 2 ,10 and H 2 PtCl 6 11.…”

“…1,2 Particularly, studies on the hydrosilylation reaction of carbonyl groups from ketone and aldehyde are well illustrated in the literature. [3][4][5][6][7] It was reported that the yield of the hydrosilylation reactions depends mainly on the catalyst nature such as UV light, 8 metal halides, NiCl 2 , 9 ZnCl 2 , 10 and H 2 PtCl 6 . 11 Transition-metal salts and complexes catalysts were described as very efficient catalysts for the hydrosilylation reaction.…”

“…11 Transition-metal salts and complexes catalysts were described as very efficient catalysts for the hydrosilylation reaction. For example, Eaborn et al 12 compared the catalytic efficiency of ruthenium and rhodium complexes and more precisely RuCl 2 (PPh 3 ) 3 and RhCl(PPh 3 ) 3 . They reported that silylethers are successfully obtained from aliphatic ketone with the ruthenium complexes.…”

2-Alkoxy-3,4-dihydropyrans as modular substrates to construct polyheterocycles by reacting with NH2-containing bisnucleophiles

“…Cyclohexyl 3-oxobutanoate was synthesized through transesterification reaction according to literature method. 12 Dihydropyrans were prepared according to literature's method. 6a 4.2.…”