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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.