Table 12. Comparison of SMA's catalytic efficiency for the synthesis of 4a with that of other catalytic systems.

Catalyst	Amount of catalyst	Yield (%)	Solvent	Time (min)	Temperature (°C)
SmCl3 (ref. 57)	20 mol%	98	—	540	120
CAN59	5 mol%	96	PEG 400	240	50
SbCl3/SiO2 (ref. 60)	10 mol%	93	—	50	120
Sr(OTf)2 (ref. 61)	10 mol%	85	DCM	300	80
H14[NaP5W30O110]62	0.4 mol%	88	—	120	120
SMA (this work)	1 mol%	98	IPA	80	70