Optimization of the ATH Reaction of 1a^a.

Entry	Ru dimer	Ligand	Solvent	1a/2a/4 (%)b	dr (anti : syn)c	er (anti)d
1	Benzene	L1	CH2Cl2	5/50/20	55 : 45	88.5 : 11.5
2	Benzene	L2	CH2Cl2	21/41/16	89 : 11	7 : 93
3	Benzene	L3	CH2Cl2	35/15/5	87 : 13	12.5 : 87.5
4	Benzene	L4	CH2Cl2	<5/52/20	80 : 20	95 : 5
5	p-Cymene	L4	CH2Cl2	33/47/<5	85 : 15	90.5 : 9.5
6	Mesitylene	L4	CH2Cl2	20/65/<5	91.5 : 8.5	93 : 7
7	Hexamethylbenzene	L4	CH2Cl2	34/28/<5	83 : 17	58 : 42
8	Mesitylene	L4	MeOH	49/24/<5	86 : 14	89.5 : 10.5
9	Mesitylene	L4	CH3CN	26/37/<5	85 : 15	85 : 15
10	Mesitylene	L4	Dioxane	8/68/<5	93 : 7	95.5 : 4.5
11	Mesitylene	L4	CHCl3	13/57/<5	94.5 : 5.5	96 : 4
12e	Mesitylene	L4	Dioxane	11/68/<5	93 : 7	96 : 4
13f	Mesitylene	L4	Dioxane	15/60/<5	94 : 6	96 : 4
14g	Mesitylene	L4	Dioxane	12/72/<5	95 : 5	96.5 : 3.5

^aReactions preformed with [RuCl₂(arene)]₂ (0.1 eq.) and ligand (0.2 eq.) heated in 2-propanol (0.3 mL) at 80 °C for 1 h. After cooling to room temperature, the catalyst was then added to a solution of 1a (0.2 mmol, 1 eq.) and HCO₂H/Et₃N (1.5 : 3, 1.5 eq.) in solvent (1 mL).

^bIsolated yields.

^cDetermined by NMR analysis of the crude reaction mixture.

^dDetermined by chiral HPLC.

^eReaction run with 0.075 eq. of [RuCl₂(mesitylene)]₂ and 0.15 eq. of (S,S)-DPAE.

^fReaction run with 0.05 eq. of [RuCl₂(mesitylene)]₂ and 0.1 eq. of (S,S)-DPAE.

^gReaction run with 0.025 eq. of [RuCl₂(mesitylene)]₂ and 0.05 eq. of (S,S)-DPAE.