Table 1 Optimization of benzylic oxidation of 4a.

From: Activated carbon for aerobic oxidation: Benign approach toward 2-benzoylbenzimidazoles and 2-benzoylbenzoxazoles synthesis

Entry

Solvent

Atm.

Temp (°C)

Yield b 5

(%) 6

1

EtOH

air

r. t.

5.2c

5.6c

2

EtOH

 

r. t.

7.9c

6.3c

3

EtOH

 

50

8.3

5.9

4

MeOH

 

50

11.1

1.4

5

Acetonitrile

 

50

12.0

6.1

6

Acetone

 

50

7.1

8.2

7

EtOAc

 

50

11.2

7.9

8

THF

O2

50

5.4

5.5

9

Toluene

 

50

<1

5.3

10

m-Xylene

 

50

<1

3.4

11

H2O

 

50

6.7

4.2

12

H2O

 

70

11.4

8.4

13

H2O

 

85

31.6

29.5

14

solvent-free

 

85

8.5

12.7

  1. aReaction conditions: 4 (2 mmol), AC III (Aladdin Inc., 60 mg) and solvent (5 mL).
  2. bYields were based on HLPC analysis.
  3. cIsolated yields for 12 h.
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