Nature Communications

Table 1 Optimization of the CPA-catalyzed aminalization

From: Organocatalytic asymmetric synthesis of Tröger’s bases


Entry^[a]	CPA	Solvent	Additive	Temp./°C	Time/h	Yield/%^[b]	ee/%^[c]
1	C1	CH₂Cl₂	-	25	8	60	0
2	C2	CH₂Cl₂	-	25	8	64	17
3	C3	CH₂Cl₂	-	25	8	57	0
4	C4	CH₂Cl₂	-	25	8	90	28
5	C5	CH₂Cl₂	-	25	8	95	52
6	C6	CH₂Cl₂	-	25	8	80	6
7	C7	CH₂Cl₂	-	25	8	50	9
8	C5	CH₂Cl₂	-	0	14	94	63
9	C5	CH₂Cl₂	-	−10	20	94	66
10	C5	CH₂Cl₂	-	−20	22	91	64
11	C5	CH₂Cl₂	-	−40	24	84	54
12	C5	CHCl₃	-	−10	20	91	73
13	C5	DCE	-	−10	20	89	64
14	C5	toluene	-	−10	26	86	59
15	C5	THF	-	−10	24	90	67
16	C5	CH₃CN	-	−10	22	48	45
17	C5	CHCl₃	3 Å MS^[d]	−10	22	92	86
18	C5	CHCl₃	4 Å MS^[d]	−10	22	91	85
19	C5	CHCl₃	5 Å MS^[d]	−10	21	94	80
20^[e]	C5	CHCl₃	3 Å MS^[d]	−10	17	88	90
21^[e]	C5	CHCl₃	3 Å MS^[d]	−20	20	95	92
22^[e]	C5	CHCl₃	3 Å MS^[d]	−40	24	96	96

^[a] Unless otherwise indicated, the reaction conditions were as follows: 1a (0.05 mmol, 1 equiv), 2 (0.06 mmol, 1.2 equiv), and CPA (5 mol%) in the specified solvent at the given temperature for 24 h. ^[b] Isolated yield. ^[c] Determined by chiral HPLC analysis. ^[d] 100 mg. ^[e] 2b was used.

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