Aluminum-catalyzed efficient synthesis of anilides by the acylation of aryl amines under ultrasonic conditions

Figures & data

short-legendScheme 1. Synthesis of anilides by the acylation of aryl amines under ultrasonic condition.

Table 1. Solvent optimization for the synthesis of 3j under sonic condition at 25°C using 5 mmol of aluminum powder.

Entry	Solvent	Time (sec)	Yield (%)
			Normal	US
1	ether	330	25	41
2	EtOH	350	20	55
3	MeCN	80	22	93
4	THF	335	21	60

Table 2. Amount of Al optimization for the synthesis of 3j under ultrasonic irradiation at 25°C in 10 mL MeCN.

Entry	Amount of Al (mmol)	Time (sec)	Yield (%)
1	3	80	40
2	4	80	65
3	5	80	93
4	6	80	90
5	7	80	87
6	–	1800	ND
ND, not detected.

Table 3. Reaction of aryl amines with different acid chlorides.

Entry	Aniline (1)	Acid chloride (2)	Time (sec)	Product^A (3)	Yield^B (%)	M. P (°C) Ref 31–33
a			135		90	159–160
b			140		96	191–192
c			120		95	184–186
d			120		92	155
e			135		86	141–142
f			170		88	116
g			145		92	133
h			150		94	153
i			155		92	107–109
j			80		93(20)^C	134–136
k			150		86	99
l			140		92	115–117
m			160		90	162
n			135		87	122–124
o			145		85	211
p			140		93(20)^D	200
q			120		95	122–124
r			135		97	118
s			125		91	185
t			135		90	168–170
^AAll the product were characterized by physical and spectral (IR, GC–MS and ^1HNMR) analysis and found to be in accordance with the assigned structures
^BIsolated yield
^CA mixture of benzoyl chloride (1.410 g, 10 mmol), 4-toludine (1.07 g, 10 mmol), aluminum metal powder (0.135g, 5 mmol) in MeCN (10 mL) were stirred at 25°C for 30 min to get 20% product.
^DThe yield of the product under mechanical stirring.

Table 4. Comparison of catalytic activity of present method with reported methods.

Entry	Solvent system/catalyst	Condition	Time	Yield (%) [refs.]
a	poly(4-vinylpyridine/n-hexane/K2CO3	Rt	9 hr	91 31
b	Et3N/AcOH/Zn	40°C	4 hr	64 32
c	N-Acylbenzotriazoles/CHCl3	MW	10 min	91 33
d	TEP-4-DMAP/pyridine	Reflux	7 hr	76 34
e	Al atom/MeCN	Rt & US	80 sec	93^A
^APresent method: a mixture of benzoyl chloride (1.410 g, 10 mmol), 4-toludine (1.07 g, 10 mmol), aluminum metal powder (0.135g, 5 mmol) in MeCN (10 mL) were sonicated (35kHz) at 25°C for 80 sec.

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