Table 1. Optimization of the Synthesis of Pyrazolone 13.

entry	catalyst	solvent	time [h]	yielda [%]
1		AcOH	12b	5
2		EtOH	24b	trace
3	Zn(NTf2)2	toluene	24b	0
4	DMAP	toluene	24b	17
5	p-TsOH	toluene	24b	59
6	AgOTf	toluene	24b	43
7	T3P in DCM	toluene	24b	72

^aIsolated yields.

^bReflux.