Table 1. Catalyst Test for the Enantioselective Hydrogenation of Isocoumarins^a.

entry	precatalyst	time (h)	yield (%)b	e.r.c
1	C1	24	trace	ND
2	C2	24	trace	ND
3	C3	18	80	98:2
4	C4	18	83	98.5:1.5
5	C5	18	80	97:3
6	C6	18	78	96:4
7	C4a	18	65	72:28

^aReactions were carried out with 1a (0.2 mmol), the indicated ruthenium complex (0.004 mmol, 2 mol %), and NaOt-Bu (0.02 mmol, 10 mol %) in n-hexane (4.0 mL) under 50 bar of H₂ at 15 °C for the indicated time.

^bIsolated yields.

^cDetermined by HPLC analysis using a chiral stationary phase.