Table 1 Optimization of the reaction conditions.[a].

From: Zinc chloride-catalyzed cyclizative 1,2-rearrangement enables facile access to morpholinones bearing aza-quaternary carbons

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Entry

Cat.

Solvent

T (°C)

Yield (%)[b]

1

TFA

DCE

80

trace

2

TfOH

DCE

80

trace

3

p-TSA

DCE

80

trace

4

BF3·Et2O

DCE

80

trace

5

Mg(OTf)2

DCE

80

17

6

InCl3

DCE

80

30

7

ZnCl2

DCE

80

55

8

Zn(OTf)2

DCE

80

36

9

ZnBr2

DCE

80

53

10

ZnI2

DCE

80

41

11

ZnCl2

THF

80

trace

12

ZnCl2

CH3CN

80

26

13

ZnCl2

CHCl3

80

37

14

ZnCl2

DCE

80

45[c]

15

ZnCl2

DCE

100

61

16

ZnCl2

DCE

60

trace

  1. [a]Conditions: 1a (0.10 mmol), 2a (0.12 mmol), Cat. (0.02 mmol), solvent (c 0.1 M), sealed tube, argon, 12 h.
  2. [b]Isolated yields.
  3. [c]ZnCl2 (10 mol%) was used.
  4. PMP p-methoxyphenyl, DCE 1,2-dichloroethane.
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