Skip to main content

Table 2 Isolated yields for the microwave-assisted condensation of benzaldehydes 6 or naphthaldehydes 8 with thiosemicarbazide 5 and comparison with traditional methods

From: Microwave-assisted synthesis and antioxidant properties of hydrazinyl thiazolyl coumarin derivatives

Entry Compound R1 R2 R3 R4 Yield% under microwave irradiation Yield% using traditional conditions
1 7a OH H H H 70 69
2 7b H OH H H 82 66
3 7c H H OH H 71 71
4 7d OH H OH H n/a 76
5 7e OH H H Br 78 64
6 7f OH OMe H H 72 69
7 9a H - - - 92 67
8 9b OH - - - 72 62
  1. Isolated yield after microwave dielectric heating in EtOH at 120°C for 10 min (hold time) in a sealed tube using a CEM Discover single-mode microwave synthesizer by moderation of the initial magnetron power (20–150 W), followed by purification by recrystallization (EtOH). Isolated yield after reaction by traditional conductive heating at reflux in MeOH in the presence of AcOH for 1–4 h and purification by recrystallization (EtOH or EtOH–CHCl3) (see reference 20 for details). n/a Experiment not investigated.