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Solvent-free synthesis of 4H-pyranonaphthoquinones using highly active and stable

polymer grafted layered double hydroxides (LDHs-g-POEGMA) as an efficient and

reusable heterogeneous catalyst

Suresh Kumar Krishnammagaria● Seung Min Leeb● Yeon Tae Jeonga*

aDepartment of Image Science and Engineering, Pukyong National University, Busan 608-737, Republic of Korea

bLED Convergence Engineering Department, Specialized Graduate School Science and Technology Convergence,

Pukyong National University, Busan 608-737, Republic of Korea

*Corresponding author. Tel.: +82-51-629-6411; fax: +82-51-629- 6408;

E-mail: ytjeong@pknu.ac.kr

Supporting Information

Table of contents

1. Experimental ………………………………………….......................................................................................S2

2. Procedure for the synthesis of poly (oligoethylene glycol methacrylate)-g-layered double hydroxides (LDHs-g-

POEGMA): …………………………………………………………………………………………………….S2

3. General procedure for the synthesis of benzo[g]chromene-5,10-diones (4a-aa) ………………………………S4

4. 1H and 13C NMR spectra’s of benzo[g]chromene-5,10-diones (4a-aa)………………………………………...S5

5. HRMS spectra’s of 4y, 4z, 4aa ……………………………………………………………………………….S32

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1. Experimental

Chemicals were purchased from Aldrich and Alfa Aesar Chemical Companies and used without further

purification. NMR spectra were recorded in parts per million (ppm) in CDCl 3 or DMSO-d6 on a Jeol JNM ECP 400

or Jeol JNM ECP 600 NMR instrument using TMS as internal standard. Standard abbreviations were used to denote

signal multiplicities (s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet and brs = broad singnal) and the

coupling constants are given in hertz (Hz). Mass spectra were recorded on a Jeol JMS-700 mass spectrometer. All

melting points were determined using open capillaries on an Electrothermal-9100 (Japan) instrument and are

uncorrected.

2. Procedure for the synthesis of poly (oligoethylene glycol methacrylate)-g-layered double

hydroxides (LDHs-g-POEGMA)[1]

Scheme 1 Schematic presentation of synthesis of poly (oligoethylene glycol methacrylate)-g-layered double hydroxides (LDHs-g-POEGMA).

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Synthesis of Layered doubles hydroxides (LDHs)

LDHs were synthesized via co-precipitation method by one-pot reaction [2]. In a typical run, to an aqueous solution

containing a calcium salt (Ca(NO3)2.4H2O) and an aluminum salt (Al(NO3)3.9H2O) with the Ca/Al molar ratio of 2.0

was added dropwise to the 2M NaOH aqueous solution in a 250 mL RB flask at 65°C under vigorous stirring. The

metal concentration and pH of the solution were adjusted to 0.66 mol.L-1 and 11.5±0.1 respectively. The slurry

solution was aged for 18 h at 65 °C and then filtered, washed with deionized water several times and dried overnight

at 100 °C. Then the LDHs was obtained as white powder.

Anchoring of BTPT onto LDHs surface (LDHs-BTPT)

The mixture of 0.7g of LDHs and 20 mL of dry toluene was stirred at 100 °C. Then, 0.724 g (2 mmol) of BTPT in

10 mL dry toluene was injected into the flask under N2. The reaction was conducted for 24 h. The crude product was

filtered off and washed with DCM for three times to remove all unreacted BTPT. The final product was dried under

vacuum overnight.

Preparation of LDHs-g-POEGMA by RAFT polymerization

2 g of PEGMA, 0.3 g of LDHs-BTPT, 20 mg of AIBN, and 4 mL of dry toluene were placed in a round bottom

flask. The polymerization reaction was performed at 80 °C for 24 h under N2. The mixture was precipitated in

diethyl ether and washed three times with methanol. The product was dried under vacuum at 40 °C overnight (yield,

60%).

Reference

[1] M.V. Reddy, N.T. Kim Lien, G.C.S. Reddy, K.T. Lim, Y.T. Jeong, Green Chem. 18, 4228 (2016).

[2] Y. Kuwahara, K. Tsuji, T. Ohmichi, T. Kamegawa, K. Moria, H. Yamashit, Catal. Sci. Technol.2, 1842 (2012).

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3. General procedure for the synthesis of benzo[g]chromene-5,10-diones (4a-aa).

A mixture of 2-hydroxy-1,4-naphthoquinone (1, 1 mmol), 4-bromobenzaldehyde (2b 1 mmol), (E)-N-

methyl-1-(methylthio)-2-nitroethenamine (3, 1 mmol) and silica-supported tungstic acid (STA) (10 mol%) was

stirred at 80 oC under solvent-free conditions. The progress of the reaction was monitored by TLC. After completion

of the reaction, the reaction mixture was washed with ethanol. The residue dissolved in DCM, and the insoluble

STA was separated by simple filtration and washed with DCM. The solvent was evaporated under reduced pressure

and the obtained crude was recrystallized from ethanol to afford the pure yellow products (4b). The recovered

catalyst was washed with ethanol and acetone, dried and reused. The same procedure adopted for the preparation of

4a-4aa. All the products were characterized by their melting points, 1H NMR, and 13C NMR spectra. A detailed

description of spectral data for all compounds 4a-4aa is given in below.

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4. 1H and 13C NMR spectra’s of benzo[g]chromene-5,10-diones (4a-aa).

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5. HRMS spectra’s of 4y, 4z, 4aa

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