Green synthesis of quinoxaline derivatives using p-dodecylbenzensulfonic acid as a surfactant-type Bronsted acid catalyst in water

Figures & data

short-legendScheme 1. DBSA catalyzed synthesis of quinoxalines.

Table 1. Effect of solvents on the synthesis of 2,3-diphenylquinoxaline.^a

Entry	Solvent	Time (h:min)	Yield (%)
1	H2O	2:00	96
2	EtOH	2:00	87
3	EtOH/H2O	2:00	93
4	MeOH	2:00	86
5	n-Hexane	2:00	75
6	Acetonitril	2:00	87
^aBenzil (1.0 mmol), o-phenylenediamine (1.0 mmol) in the presence of DBSA (10 mol%) at room temperature in various solvents.

Table 2. Effect of different surfactants on the reaction time and yield of 2,3-diphenylquinoxaline.^a

Entry	Surfactant	Time (h:min)	Yield (%)
1	DBSA	2:00	96
2	CTAB	3:30	85
3	TTAB	5:00	85
4	DTAB	4:00	86
5	Esterquat	3:00	76
^aBenzil (1.0 mmol), o-phenylenediamine (1.0 mmol) in the presence of 10 (mol%) of various surfactants.

Table 3. Effect of amount of DBSA on the reaction times and yields.^a

Entry	DBSA (mol%)	Time (h:min)	Yield (%)
1	0	24	–
2	5	2:10	92
3	10	2	96
4	20	2	96
^aReaction conditions: benzil (1.0 mmol), o-phenylenediamine (1.0 mmol) in the presence of various amount of DBSA at room temperature in water.

Table 4. Effect of different Bronsted acids on the synthesis of 2,3-diphenylquinoxaline.^a

Entry	Catalyst	Time (h:min)	Yield (%)
1	DBSA	2:00	96
2	HCl	2:00	85
3	PTSA	4:00	90
4	H2SO4	4:00	80
5	H3PO4	2:30	84
^aBenzil (1.0 mmol), o-phenylenediamine (1.0 mmol), catalyst (10 mol%) at room temperature in water as solvent.

Table 5. Synthesis of quinoxaline derivatives using DBSA as a BASC.

Entry	1,2-Dicarbonyl	1,2-Diamine	Product	Time (h)	Yield (%)^a,b	Mp (°C)
1				2	96	126–127
2				2	92	151–152
3				6	90	191–192
4				6	86	192–194
5				2	93	117–118
6				2	94	125–127
7				2	95	242–244
8				2	93	240–242
9				10	98	133–135
10				2	98	218–219
11				10	94	129–132
12				1	95	129–131
13			–	24	0	–
^aRefers to isolated yields.
^bAll products were characterized by spectra and physical data.