A green development of Bernthsen 9-substituted acridine synthesis in the absence of solvent catalyzed by p-toluenesulphonic acid (p-TSA)

Figures & data

short-legendScheme 1. Traditional Bernthsen acridine synthesis.

short-legendScheme 2. Synthesis of a 9-substituted acridines using catalyst under microwave radiation.

Table 1. Screening of catalysts for the synthesis of 9-(phenyl)acridine via Scheme 2.

		Under microwave irradiation		Thermal heating
Entry	Catalysts	Power/reaction time (min)	Yield (%)^a,b	Reaction time (hr)	Yield (%)^a,b
1	p-Toluenesulfonic acid	450/4	80	12	75
2	Ceric ammonium nitrate	600/12	31	20	30
3	Basic alumina	600/12	25	20	27
4	Zirconium oxychloride octahydrate	600/12	–	20	–
5	Potassium dichromate	600/12	–	20	–
6	Anhydrous aluminium chloride	600/12	–	20	–
^aIsolated yield.
^bAll the products were characterized by IR, ^1H NMR, ^13C NMR and mass spectrometry, elemental analysis, and mp.

Table 2. p-TSA catalyzed synthesis of acridine derivatives via Scheme 2.

			Under microwave irradiation		Thermal heating
Entry	Acid/acid anhydride	Stoichiometry (DPA:acid moiety)	Power/reaction time (min)	Yield (%)^a,b	Reaction time (hr)	Yield (%)^a,b
1	R = − C6H5	1:1	450/4	80	12	75
2	R = p-ClC6H4	1:2	600/2	84	10	73
3	R = o-ClC6H4	1:2	600/2.5	82	10	73
4	R = p-NO2C6H4	1:2	600/7	74	15	42
5	R= p-NH2C6H4	1:2	600/9	66	15	38
6	R = p-OHC6H4	1:2	450/7	49	12	20
7	R = o-C6H4COOH	1:2	450/3.5	84	10	64
8	R = − CH2COOH	1:2	600/5	48	10	31
9	R = −(CH2)2COOH	1:2	600/3	78	10	67
10	R = −(CH2)4COOH	1:2	300/2.5	88	10	71
11	C6H4(CO)2O	1:1	450/3	79	10	67
^aIsolated yield.
^bAll the products were characterized by IR, ^1H NMR, ^13C NMR and mass spectrometry, elemental analysis, and mp.