Table 4.

Synthesis of 3-(methoxycarbonyl)coumarin (3) in undried [MMIm][MSO₄] with or without L-proline as promoter.

Run	L-proline [equiv.]	T [°C]	Time [h]	Yield [%]
1	-	90	18	-
2	0.2	90	4.5	96
3	0.5	90	1	90
4	1	90	0.5	98
5	1	70	2	90
6	1	50	6	80