Chemistry & Biology Interface

Chemistry & Biology Interface, 2020, 10, 4, 96-103 RESEARCH PAPER ISSN: 2249 –4820 CHEMISTRY & BIOLOGY INTERFACE An official Journal of ISCB, Journal homepage; www.cbijournal.com An expeditious synthesis of 1,3-oxazine and Betti bases catalyzed by aqueous extract of Acacia concinna pods as an efficient surfactant type catalyst Vinod R. Kadu1, and Somnath S. Gholap*1,2 1Department of Chemistry, Padmashri Vikhe Patil College of Arts, Science and Commerce, Pravaranagar, A/P- Loni(kd), Tal.- Rahata, Dist.- Ahmednagar, Pin-413713 (MS), India. 2Department of Chemistry, Arts, Commerce and Science College, Satral (Affiliated to SPPU, Pune) Tal.- Rahuri, Dist.- Ahmednagar, Pin-413711 (MS), India. *Corresponding Author E-mail: [email protected] Received 28 October 2019, Accepted 1 August 2020 Abstract: An efficient and simple procedure for the synthesis of 1,3-oxazines and Betti basesvia Mannich type reaction was successfully carried out in aqueous extract of Acacia concinna pods as a green alternative. The present surfactant catalyst was found to be expeditious in terms of economic viability, mild reaction conditions, good to excellent product yield and environment friendliness. Keywords: Natural surfactants, Acacia concinna, Betti bases, 1,3-oxazines, green protocol. INTRODUCTION to have remarkable biological potential [4–6]. Moreover, the catalytic properties of these The identification and characterization of new surfactants have been extensively studied. catalysts isolated from natural resources has Specifically, the plant cell culture of Daucus been enormously increasing to overcome various carota root [7–12], soaked Phaseolus Aureus environmental constraints. These catalysts play (green grams) [13], and coconut juice (Cocos an important role in acceleration of rate of the Nucifera) [14] has been successfully utilized as chemical reactions as well as ease of isolation biocatalysts for selective reduction of ketones. In of the final product. Nowadays, numerous the previous reports, aqueous extract of Acacia natural and synthetic materials like supercritical concinna has been utilized for the synthesis solvent, ionic liquids, clays, enzymes and of 3-carboxycoumarins, cinnamic acids [15], surfactants are extensively recognized as an acylation of amines [16] and synthesis of aryl- alternative to the traditional expensive and toxic hydrazones [17]. catalyst and reagents [1-3]. The surfactants isolated from natural sources are well known Oxazine derivatives exhibits broad range of Chemistry & Biology Interface 96 Vol. 10 (4), July - August 2020 Chemistry & Biology Interface, 2020, 10, 4, 96-103 bioactivities including anticancer (A and B), The classical Betti reaction involved the two antibacterial (C), anticonversant, antitubular, step reaction of aldehyde, ammonia or urea and non-nucleoside reverse transcriptase inhibitor β-naphthol in an ethanolic solution of potassium (efavirenz) (D), drug (Ketazolam) (E) [18] hydroxide for 9–36 h [26,31]. Consequently, (Figure 1), anti HIV-1 [19], anti-Parkinson’s several recent reports on Betti reaction have agents [20]. Due to broad range of bioactivities been developed to overcome the drawbacks of associated with these class of compounds, their the classical method. Therefore, the preferable synthesis is the major concern. Traditionally, route will be multicomponent reaction of 1,3-oxazine derivatives can be synthesised by aldehyde, amine and phenol [26,32,33]. Herein, using two step process from primary amines, we have reported the sustainable synthesis of aldehyde and phenols [21]. Although, several Betti bases catalysed by aqueous extract of methods are reported so far for the synthesis Accacia concinna. of target compounds [22–24], only limited numbers of protocols are feasible on the basis of the multi component reactions (MCRs) [25]. Acacia concinna (commercially known as “Shikakai” in India) pods have surfactant R N properties since it contains saponins, which are O OH CH3 CH3 CH3 A- γ -Tocotrienol: R = CH3 foaming agents [34,35]. In addition, there is H3C O CH3 B- δ-Tocotrienol: R = (CH2)6OH CH3 presence of acacic acid as one of the chemical Anticancer agent constituent in the aqueous extract of pods of O O R2 F3C N Acacia concinna [36]. In present protocol N Cl O R1 N O catalytic activity of the natural surfactant was R1= Ph, R2 = H N O Cl Ph O R1= Br, R2 = Br H studied for the synthesis of 1,3-oxazine and C D E Betti bases. Figure 1. Result and Discussion Betti reaction is one of the most important C-C bond-forming reactions, which is typically In the present study, a simple, cost effective and a Mannich reaction [26]. Betti bases have green protocol for the synthesis of Betti bases associated with various synthetic and biological and 1,3-oxazine derivatives using an aqueous applications. They have exihibited various extract of pods of Acacia concinna has been pharmacological properties like anti-bacterial, reported (Scheme 1 and 2). The methodology antipain and antihypertensive activities [27–30] presented here is in persistence of our ongoing (Figure 2). research on construction of novel synthetic method for biologically active compounds [37]. R R1 O Ar N N R' N Aq. extract of OH OH O H R N Acacia Concinna (20%) + + OH OH Ar H R' RT,1-2.5 h 1 2 3 4(a-x) R R2 R1=H,Me,Cl,OMe R=H,CONHNH2,COOMe, Scheme 1. Synthesis of Betti Bases by using R2=H, 6-Br, 6-OMe, 5-COOH COOH,COOPh,NH2 2-naphthol Figure 2. Biologically active Betti bases. Initially, efficiency of the catalyst was studied by Chemistry & Biology Interface 97 Vol. 10 (4), July - August 2020 Chemistry & Biology Interface, 2020, 10, 4, 96-103 conducting reaction of β-naphthol (1) (1mmol), for the synthesis of structurally diversified benzaldehyde (2a) (1 mmol) and piperidine (1 Betti bases. Moreover the catalytic property mmol) using surfactant catalyst (20% w/v, 5 of natural surfactant might be attributed due to mL) aqueous extract of Acacia concinna pods the presence of saponins which solubilises the at room temperature and we were pleased to get reactant molecules in aqueous surfactant. This an admirable yield of product 4a (94%) after may alters the number of favourable collisions 1 h. The above outcome encouraged us for the among the reactant molecules. The surfactant optimization the reaction conditions for the same property of extract leads to encapsulation of reaction in presence of different concentrations the reactants in micellar cages. This process aqueous extract of Acacia concinna pods. of encapsulation drives the equilibrium toward The results obtained suggested that 20% of product side by expelling the water molecule the catalyst concentration was adequate to out of its hydrophobic interior (Figure 3 and get maximum yield of the product. Further, 4) [15]. increase in catalyst concentration as 30, 40 and 50% did not affected the yield of final product. Table 1. Optimization of catalyst The result obtained was summarised in Table concentration for formation of ‘4a’ 1. In order to estimate the catalytic strength of the present catalyst various surfactants like Entry Catalyst concentration (%) Time (h) Yield(%)a sodium dodecyl sulphate (SDS), triton X-100 1. 10 1.25 89 and cetyl pyridinium bromide (CPB) were used. It has been observed that when the reaction was 2. 20 1 94 conducted in the presence of sodium dodecyl 3. 30 1.50 93 sulphate (SDS) as an anionic surfactant, the product ‘4a’ was obtained in 64% yield (Table 4. 40 1.40 92 2, entry 2). With other surfactants such as 5. 50 1.35 92 Triton X-100 and cetyl pyridinium bromide 6. Catalyst free 12 --b (CPB) did not showed appreciable results (Table 2, entries 3, 4). Therefore the present aIsolated yield of the product, bNo product formation was observed. surfactant catalyst was found to be superior H2O Ar H2O R N R A O H2O R B R N R' 9 OH H O O H R 2 R N Ar R H R' O N 4 Ar NH 2 R H2O H2O 10 H2O 4, 9: A = H, B = OH 4: R = Ar 10: A = OH, B = H 9, 10: R = H Figure 3. Micelle-promoted synthesis of Betti bases and oxazine derivatives Chemistry & Biology Interface 98 Vol. 10 (4), July - August 2020 Chemistry & Biology Interface, 2020, 10, 4, 96-103 Table 2. Effect of surfactant for the Table 3. Effect of surface tension of surfactant formation of ‘4a’ solution on rate of reaction a b Catalyst Surface Entry Surfactant Time (h) Yield (%) Time Entry concentration Tension ‘T’ (h) 1. None 12 --c %(w/v) (dyne/cm) 2. SDS 2.25 64 1. 50 1.35 13.48 3. Triton X-100 2 56 2. 40 1.40 18.87 4. CPB 2.5 45 3. 30 1.50 32.34 Acacia concinna extract 5. 1 94 4. 20 1 40.43 20% (w/v) 5. 10 1.25 48.51 aReaction condition: 2-naphthol(1) (1mmol), benzaldehyde (2) (1 mmol) and piperidine (3) (1 mmol), room temperature. bIsolated yield. cNo reaction. 6. Distilled Water -- 67.38 The desired Betti bases were obtained in admirable yields. Chemically reactive substrates like thiophene-2-aldehyde underwent smooth reaction to produce corresponding Betti bases without any side product formation (Table 4, Entry-19). In general, all amines undergo multi-component condensation afforded corresponding Betti bases. OH R N 7 Surfactant catlyst (20%) O RT, 1-2.5 h Figure 4. Photograph of micelle observed in NH2 reaction medium during formation of ‘4a’ 9(a-h) + 2 HCHO R OH 6 Surfactant is found to decrease the surface 5 O N R tension of aqueous solution which increases 8 wetting and spreading properties of water Surfactant catlyst (20%) RT, 1-2.9 h (Table 3) [38]. A several reactions such as 10(a-c) redox, photochemical, enzymatic, Diels-Alder, photochemical etc are altered due to decrease Scheme 2.

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