Functionalized silica nanoparticle/support-catalyzed synthetic protocol of 1,4-DHP and its derivatives^a.

Entry	Catalyst	Temperature (°C)/Ultrasonic probe (W)	Solvent	Time	Yieldb (%)	Ref.
1	Ultrasound SnCl4@nano-SiO2	40	EtOH	5 min	96	50
2	[βCD/Im](OTs)2-silica	90	Solvent free	15 min	98	51
3	SO3H-KIT-5	Room temperature	Solvent free	60 min	87	52

^aReaction conditions: aldehyde (1.0 mmol), NH₄OAc (1–1.5 mmol), dimedone (2.0 mmol).

^bIsolated yields.