Table 2. Palladium-Catalyzed Hydrogenation of Testosterone in the Presence of Tetrabutylammonium-Based Ionic Liquids and Salts^a.

entry	additive	isolated yield (%)b	drc
1		82	61:39
2	[TBA][l-prolinate]	27	80:20
3d	[TBA][l-prolinate]	41	86:14
4e	[TBA][l-prolinate]	70	75:25
5d	[TBA][l-alanate]	32	84:16
6	[TBA][l-mandelate]	94	82:18
7	[TBA][d-mandelate]	99	84:16
8	[TBA][l-lactate]	92	85:15
9	[TBA]2[l-malate]	75	84:16
10	[TBA][l-hydrogenmalate]	n.d. (72)	85:15
11	TBA acetate	99	78:22
12	TBA benzoate	98	84:16
13	[emim][l-lactate]	99	80:20
14	[Ch][l-lactate]	n.d. (95)	75:25
15f	[TBA][d-mandelate]	94	84:16
16g	[TBA][d-mandelate]	99	84:16
17h	[TBA][d-mandelate]	83	84:16
18i	[TBA][d-mandelate]	n.d. (92)	85:15

^aReaction conditions: 200 mg of IL, 1 mmol of steroid, 0.01 mmol (1 mol %) of PdCl₂, mass ratio of iPrOH/IL = 5, 18 h, rt, 1 bar H₂.

^bIsolated yield of the 2a/3a mixture after chromatography. The number in parentheses shows the conversion of testosterone, determined by quantitative ¹H NMR measurement.

^cThe diastereomeric ratio (dr) was determined by quantitative ¹H NMR measurement.

^dSolvent: iPrOH/water (10% v/v) mixture.

^eSolvent: iPrOH/water (30% v/v) mixture.

^f0.02 mmol (2 mol %) of PdCl₂.

^gReaction time: 2h.

^hMass ratio of iPrOH/IL = 2.

ⁱMass ratio of iPrOH/IL = 1.