Table 1 Reaction optimization^a,b


Entry	Variation from standard conditions	yield/%
1	none	61
2	CpTiCl₃ instead of Cp₂TiCl₂	19
3	salen-Ti I instead of Cp₂TiCl₂	47
4	salen-Ti II instead of Cp₂TiCl₂	58
5	salen-Ti III instead of Cp₂TiCl₂	81
6	salen-Ti IV instead of Cp₂TiCl₂	91(89)^c
in entries 7–18, salen-Ti IV (5 mol%) was used
7	CH₃CN instead of 1,4-dioxane	70
8	DCM instead of 1,4-dioxane	56
9	EtOAc instead of 1,4-dioxane	48
10	THF instead of 1,4-dioxane	83
11	Et₂O instead of 1,4-dioxane	39
12	2,4,6-collidine•HCl instead of Et₃N•HCl	26
13	Zn instead of Mn	83
14	Mn (50 mol%)	44
15	Et₃N•HCl (50 mol%)	53
16	no Et₃N•HCl	17
17	no Mn	0
18	no Ti-catalyst	0

^a Reaction scale: 1a (0.2 mmol, 1equiv), 2a (1.5 equiv). ^b Yields were determined by ¹H NMR spectroscopy vs. an internal standard (1,2,3-trimethoxybenzene) ^c isolated yield. CH₃CN Acetonitrile, DCM Dichloromethane, EtOAc Ethyl acetate, THF Tetrahydrofuran, Et₂O Diethyl ether.

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