Communications Chemistry

Table 1 Optimization of the reaction conditions of asymmetric carbo-acylation of alkenes.

From: Nickel-catalyzed enantioselective reductive carbo-acylation of alkenes


Entry	Precatalyst	Ligand	Solvent	Reductant	Yield (%)	ee (%)
1	NiBr₂·glyme	L2	EtOH	Zn	29	26
2	NiBr₂	L2	EtOH	Zn	0	–
3	NiBr(COD)₂	L2	EtOH	Zn	28	24
4	Ni(acac)₂	L2	EtOH	Zn	0	–
5	NiI₂	L2	EtOH	Zn	trace	–
6	NiBr₂·glyme	L1	EtOH	Zn	9	71
7	NiBr₂·glyme	L1	DMA	Zn	14	60
8	NiBr₂·glyme	L1	DMA	Mn	50	64
9	NiBr₂·glyme	L1	NMP	Mn	20	54
10	NiBr₂·glyme	L1	THF	Mn	trace	–
11^a	NiBr₂·glyme	L1	DMA	Mn	62	63
12^a	NiBr₂·glyme	L3	DMA	Mn	19	33
13^a	NiBr₂·glyme	L4	DMA	Mn	50	66
14^a	NiBr₂·glyme	L5	DMA	Mn	55	63
15^a	NiBr₂·glyme	L6	DMA	Mn	44	67
16^a	NiBr₂·glyme	L7	DMA	Mn	47	57
17^a	NiBr₂·glyme	L8	DMA	Mn	trace	–
18^a	NiBr₂·glyme	L9	DMA	Mn	29	48
19^a	NiBr₂·glyme	L10	DMA	Mn	50	71
20^a	NiBr₂·glyme	L11	DMA	Mn	trace	–
21^a	NiBr₂·glyme	L12	DMA	Mn	64	85
22^b	NiBr₂·glyme	L12	DMA:NMM = 4:1	Mn	45	87
23^b	NiBr₂·glyme	L12	DMA:NMM = 2:1	Mn	trace	–
24^c	NiBr₂·glyme	L12	DMA:NMM = 4:1	Mn	65 (61)^d	88

Reactions were performed on a 0.2 mmol scale of the carbamoyl chloride 1f using 2.0 equiv of n-pentyl iodide 2a, 10 mol% [Ni], 15 mol% ligand, and 2.0 equiv of reductant in 1.5 mL solvent at r.t. for 12 h. Yields were determined by ¹NMR spectroscopy using CH₂Br₂ as an internal standard. Enantiomeric excessess were determined by HPLC analysis on chiral stationary phase.
^a1.0 equiv of ZnI₂ was used as an additive.
^b10 °C, 72 h.
^c10 °C, 96 h, NiBr₂·glyme (20 mol%), L12 (20 mol%).
^dYield of the isolated product.

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