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Table 1 Optimization of reaction conditions [a]

From: Metal-free synthesis of polysubstituted oxazoles via a decarboxylative cyclization from primary α-amino acids

Entry

Catalyst

Oxidant

Base

Temperature (°C)

Yield[b](%)

1

20% I2

TBHP

_

70

50

2

_

TBHP

_

70

trace

3

20% CuO

TBHP

_

70

41

4

10% I2

TBHP

_

70

38

5

30% I2

TBHP

_

70

49

6

20% I2

TBHP

Na2CO3

70

54

7

20% I2

TBHP

K2CO3

70

52

8

20% I2

TBHP

t-BuOK

70

12

9

20% I2

TBHP

Et3N

70

45

10

20% I2

DTBP

Na2CO3

70

49

11

20% I2

m-CPBA

Na2CO3

70

27

12

20% I2

K2S2O8

Na2CO3

70

30

13

20% I2

TBHP

Na2CO3

60

59

14[c]

20% I2

TBHP

Na2CO3

25

60

15

20% I2

TBHP

Na2CO3

25-60

70

  1. [a] The reaction mixture of 0.7 mmol of phenylglycine, 0.5 mmol of 2-bromoacetophenone, 1 mmol of oxidant and 0.5 mmol of base in 2 mL of DMA was stirred for 5 h with different catalytic loading. [b] Isolated yields based on 2-bromoacetophenone. [c] Reaction time was 24 h. DTBP = di-tert-butyl peroxide, m-CPBA = m-chloroperoxybenzoic acid.