Supporting information for the article:

One-pot multicomponent synthesis in aqueous medium of 1,4-dihydropyrano[2,3-c]-pyrazole-carbonitrile and derivatives using a green

nano SiO2 catalyst from agricultural waste

Khushbu G. Patela, Nirendra M. Misraa Rajesh H. Vekariyab, Rakshith R. Shettigara

a1Department of Sciences, School of Technology (SOT), Pandit Deendayal Petroleum University, Gandhinagr, Gujarat, India.b Department of Chemistry, School of Sciences, Gujarat University, Ahmedabad, Gujarat, India.

*Corresponding author. Tel.: 7383018992; E-mail: patelkhushbug09@gmail.com

Contents

1. Method for the preparation of Catalyst –SiO2 NPs from an agricultural waste – Wheat straw (with flow chart)2. Characterization of SiO2 NPs(i) Powder XRD spectrum of fresh WS-SiO2 NPs(ii) Particle size distribution graph Of WS-SiO2 NPs(iii) EDX study (iv) FT-IR spectra of fresh SiO2 NPs3. General method for the preparation of pyrano[2,3-c]pyrazoles derivatives(i) Table 1. Preparation of compounds pyrano[2,3-c]pyrazole (with Picture)(ii) Chromatotron analysis for purification study of compound.4. Reusability of the SiO2 NPs5. Representative 1H and 13C spectra of some compounds

1. Method for the preparation of Catalysts (with flow chart)

Fig. 1 Flow diagram for the synthesis of amorphous nano silica from wheat straw

A 5gm sample of dried wheat straw was weighed and treated with concentrated acid. The acid

treated wheat straw was filter and washed with distilled water to remove access amount of acid

and dried it at 150 oC for overnight. The cleaned wheat straw was transferred into microwave

digestion vessel (Easy Prep). For the sodium silicate preparation 10 ml 1N NaOH added in with

cleaned wheat straw. A reaction was carried out in microwave digester (MARS - version

194A07, copyright 1997, CEM Corporation) at 120 oC, 400W for 10min. The mixture was

suction filtered to obtain a light brown filtrate (sodium silicate) which was kept in glass backer.

The prepared sodium silicate solution was treated drop wise with 1N HCl with continuous

stirring to maintain pH 7-9. Precipitation occurred and a gel was formed within few minutes, no

gel observed at above pH 9 and below pH 7. The precipitated gel was recovered by centrifuge at

4000 rpm. The obtained gel was wash with distilled water and dried in hot air oven at 150 oC for

24h. .Finally, white solid residue was obtained after drying, and labeled it as WS-silica. Figure 1

shows the preparation steps of silica from wheat straw – an agricultural waste.

Fig.2 (a) Wheat straw (b) Silica (gel form) (c) Nano amorphous silica

The reaction mechanism between acid treated WS and sodium hydroxide was at below. The

reaction was carried out in a two part alkaline solubilization and neutralization. Acid treated

Wheat straw containing silica was dissolved in NaOH solution after microwave digestion

treatment and formed sodium silicate solution.

Alkaline-solubilization

Acid-neutralization

This formed sodium silicate solution treated with hydrochloric acid with continuous stirring.

Within a few minutes silica precipitation in gel formed was observed.

2. Characterization of SiO2 nano particles

(i) Powder XRD spectrum of fresh WS-SiO2 NPs

Figure S1 Powder

XRD pattern of WS-SiO2 NPs.

(ii) Particle size distribution graph of WS-SiO2 NPs

Figure S2 Particle size distribution graph by particle size analyzer of WS-SiO2 NPs

(III) EDX spectrum of WS-SiO2 NPs

Figure S3 EDX spectrum of obtained product from wheat straw for elemental analysis

Table 1 The elemental composition of WS-Silica

(IV) FTIR dpectrum

Figure S4 FTIR Spectrum of Wheat straw - Silica

Elements Atomic %Si 87.35O 11.90Na 0.75Total 100.00

3. General method for the preparation of pyrano[2,3-c]pyrazoles derivatives

In a 25 ml round bottom flask, aryl aldehydes (1mmol), hydrazine hydrate (1.5mmol), ethyl acetoacetate (1mmol), malononitrile (1mmol), 10 mol% nano SiO2 and 5 ml water was taken. This suspension was heated at the 80 °C with constant stirring. The reaction progress was monitored by TLC by using 30% ethyl acetate/hexane as a solvent system. After completion of reaction, resultant mass was poured into water and after ethyl acetate (1:1). The organic product was dissolved in ethyl acetate and separate out from the catalyst. The solid suspension was removed by filtration and wash with water. All synthesized compounds were purified by crystallization using ethanol.

(i) Table 1 Synthesis of 1,4-dihydropyrano[2,3-c]-pyrazole-5-carbonitriles catalyzed by wheat straw-Silica

Entry Aldehydes Product Picture

1 C6H5

2 4-OH-C6H5

3 2-OH-C6H5

4 4-N(Me)2-C6H4

5 3-NO2-C6H4

6 4-NO2-C6H4 -

7 4-OMe-C6H4

8 4-Cl-C6H4

9 4-CN-C6H4

10 4-Br-C6H4

11 4-Me-C6H5

(ii) Chromatotron analysis

Procedure of chromatotron for purity check of product sample

The product sample was dissolved in 30% ethyl acetate / hexane solvent system, and this solution was applied near the center of spinning disk which coated with 2mm thin layer sorbent -silica gel. The solvent forms circular bands of the separated components which are spun off from the edge of the rotor together with solvent. A novel collection system brings the eluate to a single output tube (Fig -II).  A UV transparent lid is used to direct observation of UV absorbing or colored compounds during the separation (Fig-III).

(I)

(II) (IIIFig. S5 (I) Chromatotron Instrument (II) Glass rotor (III) Chromatotron of compound 1. Sorbent

layer

Separated product

Solvent layer

The advantage by using chromatotron is separations are completed rapidly, typically within 20 min. The result shows in Fig (III) single product band was separate out on disk, it clearly shows the product was pure; no side product was form in this reaction.

4. Reusability of the SiO2 NPs

Figure S6 Powder XRD pattern of recycled WS-SiO2 NPs after 5th

cycle.

5. 1H and 13C spectra of some pyranopyrazoles compounds

NMR Spectra of entries 1,7,8 Table 4 were recorded in 1H NMR and entries 1 spectra 13C NMR were recorded in Bruker 400 MHz NMR instrument. DMSO-d6 was used as and solvent for all the NMR study.