Table 1.

Optimization of reaction conditions^a.

entry	modified reaction conditions	yields of 2 (%)b
1	none	67 (58)
2	with 1 M (0.5 mL, 0.5 mmol) HCI	0
3	with 3 M (0.5 mL, 1.5 mmol) HCI	20
4	3 h instead of 6 h	48
5	with 3 mmol p-TsOH	55
6	with 3 mmol TfOH	62
7	with 3 mmol AcOH	63

^a0.1 mmol scale reactions in 0.5 mL solvent.

^b1H NMR yields using pyrene as an internal standard. Value in parenthesis is the isolated yield from 0.5 mmol.