Comparison of different conditions for the synthesis of products 41.

Entry	Solvent	Catalyst	Temperature (°C)	Time (h)	Yield (%)
1	H2O	PEG-200	r.t.	3	55–98 (ref. 54)
2	EtOH	l-Proline	r.t.	30–72	58–98 (ref. 55)
3	—	TBAF·3H2O	60	2	55–97 (ref. 56)
4	DCM	Zn-salphen, DIPEA	r.t.	6	13–60 (ref. 57)
5	PEG-400	Cu(OAc)2	70	15–40	48–98 (ref. 58)
6	H2O	Cu(iii)	30	12–24	70–96 (ref. 59)