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

BMC Chemistry

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

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

^† 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.

ISSN: 2661-801X