An expeditious synthesis of quinoxalines by using biodegradable cellulose sulfuric acid as a solid acid catalyst

Figures & data

Scheme 1.  A mixture of benzo[c][1,2,5]thiadiazole-4,5-diamine (3.0 mmol), 2-(2-Bromo-acetyl)-benzo[f]chromen-3-one (3.0 mmol) and cellulose sulfuric acid (0.08g), r.t

Scheme 2.  A mixture of benzo[c][1,2,5]thiadiazole-4,5-diamine (3.0 mmol), substituted 3-(ω-bromo acetyl)-coumarins (3.0 mmol) and cellulose sulfuric acid (0.08g), r.t, 30min

Table 1. Yields of cellulose sulfuric acid catalyzed synthesis of quinoxalines.

Product	R 1	R 2	Time (min)	Yield (%)	Melting point
3a	H	H	20	96	245
3b	Br	H	20	94	215
3c	Cl	Cl	25	92	280
3d	Br	Br	20	91	268–269
3e	CH3	H	30	92	225–226
3f	Cl	H	20	93	210
3g	–	–	30	89	153–155

Table 2. Effect of catalysts on yield.

Entry	Catalyst	Yield^a (%)
1	Cellulose sulfuric acid	96
2	Silica sulfuric acid	92
3	Methane sulfonic acid	85
4	Sulfuric acid in acetic acid	55
5	No catalyst	15
^aYields refer to the pure isolated recovered catalyst.

Table 3. Influence of the catalytic amounts of cellulose sulfuric acid.^a

Entry	Catalyst (grams)	Time (min)	Yield^b (%)
1	None	60	Trace
2	0.01	20	28
3	0.03	20	51
4	0.05	20	79
5	0.08	40	96
6	0.08	20	96
^aHere we observed variation in yields by loading catalyst (0.01 g, yield; 28%), (0.03 g, yield; 51%), (0.05 g, yield; 79%), (0.08 g, yield; 96%).
^bisolated yield.

Table 4. Yields of recovered catalyst.

Run	Cycle	Yield^a (%)
1	0	96
2	1	95
3	2	90
4	3	82
^aYields refer to the pure isolated recovered catalyst.