A novel poly(ethyleneoxide)-based magnetic nanocomposite catalyst for highly efficient multicomponent synthesis of pyran derivatives

Figures & data

Scheme 1. Synthesis of 2-amino-4H-pyrans by using Fe₃O₄/PEO/SO₃H nanocatalyst.

Figure 1. The comparative FT-IR spectra of: Fe₃O₄, Fe₃O₄@PEO and Fe₃O₄@PEO-SO₃H.

Figure 2. (a) FE-SEM and (b) TEM images of Fe₃O₄@PEO-SO₃H nanocatalyst.

Figure 3. EDX analysis of Fe₃O₄@PEO-SO₃H nanocatalyst.

Figure 4. The XRD patterns of Fe₃O₄@PEO-SO₃H composite nanocatalyst. The symbol “*” represents the PEO-SO₃H peak.

Figure 5. VSM magnetization curves of (a) Fe₃O₄, (b) Fe₃O₄@PEO, and (c) Fe₃O₄@PEO-SO₃H.

Table 1. Optimizing of the reaction conditions in the synthesis of 4b.

Entry	Catalyst (g)	Solvent	Temperature (°C)	Time (min)	Yield^a (%)
1	–	EtOH	Reflux	240	50
2	0.005	EtOH	r.t.	25	75
3	0.007	EtOH	r.t.	25	89
4	0.008	EtOH	r.t.	25	95
5	0.01	EtOH	r.t.	25	95
6	0.008	EtOH	r.t.	35	95
7	0.008	EtOH	Reflux	30	95
8	0.008	H2O	r.t.	60	80
9	0.008	H2O/EtOH	r.t.	30	87
10	0.008	CH3CN	r.t.	30	88
11	0.008	CH3OH	r.t.	30	85
12	0.008	–	r.t.	70	82
13	0.01	–	r.t.	70	85
14	0.015	–	reflux	70	89

^aIsolated yield.

Table 2. Synthesis of 2-amino-4H-pyrans derivatives using Fe₃O₄@PEO-SO₃H nanocatalyst.

Entry	Ar	R	Product	Time (min)	Yield^a (%)	Mp (°C)
						Observed	Reported
1	Benzaldehyde	C2H5	4a	35	88	190–192	195–196 ( 6)
2	4-Chlorobenzaldehyde	C2H5	4b	20	95	174–175	171–172 ( 47)
3	4-Methylbenzaldehyde	C2H5	4c	35	88	174–176	177–179 ( 48)
4	4-Bromobenzaldehyde	C2H5	4d	30	93	178–179	175–176 ( 49)
5	4-Methoxybenzaldehyde	C2H5	4e	40	84	151–153	142–144 ( 6)
6	3-Hydroxybenzaldehyde	C2H5	4f	40	85	168–169	164–165 ( 6)
7	3-Nitrobenzaldehyde	C2H5	4g	25	93	186–187	182–184 ( 48)
8	4-Nitrobenzaldehyde	C2H5	4h	25	92	180–181	175–176 ( 50)
9	4-Nitro benzaldehyde	CH3	4i	25	91	174–176	170–172 ( 50)
10	Benzaldehyde	CH3	4j	35	83	157–158	158–160 ( 48)
11	3-Nitrobenzaldehyde	CH3	4k	25	91	197–198	204–206 ( 51)
12	4-Methoxybenzaldehyde	CH3	4l	40	85	161–163	158–160 ( 48)

^aIsolated yield.

Table 3. Comparisons of catalysts and its components effects on the model reaction.

Entry	Catalyst	Temperature (°C)	Time (min)	Yield^a (%)
1	PEO	Reflux	70	35
2	PEO-SO3H	Reflux	70	50
3	Nano- Fe3O4	r.t.	70	76
4	Nano-Fe3O4@PEO	r.t.	70	84
5	Nano-Fe3O4@PEO-SO3H	r.t.	15	95
6	–	Reflux	240	50

^aIsolated yield.

Figure 6. Recycling of Fe₃O₄@PEO-SO₃H nanocatalyst in the synthesis of 4b.

Figure 7. FT-IR spectrum of the recycling Fe₃O₄@PEO-SO₃H nanocatalyst in the synthesis of 4b.

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