Table 1. Optimization of the Reaction between Thiochroman-4-one 1a and Arylhydrazonal 2a^a.

entry	solvent	additive	T (°C)	time	product (% yield)c
1	1,4-dioxane	AcONH4	reflux	18 h
2	DMF	AcONH4	reflux	18 h
3	CH3CN	AcONH4	reflux	18 h
4	EtOH	AcONH4	reflux	18 h
5	propanol	AcONH4	reflux	18 h
6	AcOH	AcONH4	reflux	6 h	45a
7	AcOH	AcONH4	Q-tube (155 °C)b	45 min	82a
8	AcOH	AcONH4	Q-tube (160 °C)	45 min	86
9	AcOH	AcONH4	Q-tube (165 °C)	45 min	91
10	AcOH	AcONH4	Q-tube(170 °C)	45 min	93

^aReaction conditions: thiochroman-4-one 1a (5 mmol), arylhydrazonal 2a (5 mmol), and ammonium acetate (10 mmol) in acetic acid (15 mL).

^bTemperature of the oil bath.

^cIsolated yield.