Table 1.

Optimization of Alkynylation of Acetal 2a^[a]

entry	L*	base	yield(%)[b]	ee (%)[c]
1[d],[e]	L1	iPr2NEt	21	8
2[e]	L1	iPr2NEt	20	0
3	L1	iPr2NEt	83	4
4	L2	iPr2NEt	83	37
5	L3	iPr2NEt	24	27
6	L2	DBU	16	36
7	L3	DBU	32	81
8	L3	MTBD	22	84
9[f]	L3	MTBD	12	87
10[f],[g],[h]	L3	MTBD	87	78

^[a]Conditions: Acetal 2a (0.08 mmol, 1.0 equv), Cu(MeCN)₄PF₆ (0.008 mmol, 10 mol %), L*(0.01 mmol, 12 mol %), phenylacetylene (0.096 mmol, 1.2 equiv), BF_3·Et₂O (0.16 mmol, 2.0 equv), base (0.12 mmol, 1.5 equv), CHCl₃ (0.3M), −20 °C, 24 h, unless otherwise noted.

^[b]Determined by ¹H NMR analysis using 1,3,5-trimethoxybenzene as internal standard.

^[c]Determined by HPLC analysis using a chiral stationary phase.

^[d]TMSOTf (1.2 equiv) replaced BF_3·-Et₂O.

^[e]Et₂O instead of CHCl₃.

^[f]CuSPh instead of Cu(MeCN)₄PF₆.

^[g]MTBD (1.55 equiv), CHCl₃ (0.15 M).

^[h]4 °C.