Table 1 Optimization of 1,3,4-thiadiazole synthesis from nitroethane 2a and benzoylhydrazine 1aa

From: Chemoselective synthesis of 1,3,4-thiadiazoles from acyl hydrazines and nitroalkanes using elemental sulfur

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Entry

Base

Solvent

Yield of 3a (%)b

1

Na2S

THF

76

2

Na2S·9H2O

THF

84

3

Na2S·5H2O

THF

80

4

Na2S·9H2O

DMF

90

5

Na2S·9H2O

DMSO

67

6

Na2S·9H2O

CH3CN

34

7

Na2S·9H2O

MeOH

26

8

NaOtBu

DMF

40

9

Na2CO3

DMF

trace

10

Na2S·9H2O

DMF/H2O (9:1)

72

11

Na2S·9H2O

DMF/H2O (5:1)

66

  1. aReaction conditions: Nitroalkane 2a (0.4 mmol), benzoylhydrazine 1a (0.2 mmol), S8 (0.4 mmol), base (0.36 mmol), solvent (2 mL); at work up, 2 N HCl solution was added, and reaction stirred for 2 h.
  2. bYield of product were determined by 1H NMR using 1,3,5-trimethoxybenzene as an internalstandard.
  3. THF tetrahydrofuran, DMF N,N-Dimethylformamide. DMSO Dimethyl sulfoxide.
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