Table 1.

Initial Optimization.^[a]

	R	conc.[b]	temp.	time	X	yield	ee[c]
Ligand Screening
1	Ph	0.18	rt	22 h	20 (1)	78%	80%
2	Ph	0.18	0 °C	16 h	20 (L2)	26%	35%
3	Ph	0.18	0 °C	16 h	20 (L3)	36%	−66%
Time, Temperature and Catalyst Loading, X = (S,S)-1
4	Ph	0.18	rt	72 h	20	95%	79%
5	Ph	0.18	rt	48 h	10	77%	83%
6	Ph	0.18	−20 °C	45 h	10	60%	77%
7	Ph	0.18	−20 °C	45 h	5	32%	72%
Reaction Concentration, X = (S,S)-1
8	TMS	0.18	3 °C	21 h	10	35%	85%
9	TMS	0.26	3 °C	21 h	10	50%	85%
10	TMS	0.38	3 °C	24 h	10	74%	85%
11	TMS	0.69	3 °C	21 h	10	87%	75%
Catalyst Loading at Higher Concentration, X = (S,S)-1
12	Ph	0.38	3 °C	24 h	10	86%	74%
13	Ph	0.38	3 °C	24 h	5	73%	58%
14	Ph	0.38	3 °C	21 h	2.5	68%	46%

^[a]Reactions run on a 0.325 mmol scale with 2.7 or 2.8 equiv alkyne and 2.6 or 2.95 equivalents of dimethylzinc respectively. Isolated yields are reported.

^[b]Reaction concentration (in molarity) is reported with respect to the alkyne and includes the toluene added as part of the dimethylzinc solution.

^[c]Enantiomeric excess determined by chiral HPLC analysis.