Table 1 Optimization of reaction conditions

From: Photoredox cobalt-catalyzed regio-, diastereo- and enantioselective propargylation of aldehydes via propargyl radicals

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Entry

Ligand

Solvent

Yield (%)a

drb

erc

1

5a

THF

<5

NAd

NAd

2

5b

THF

26

56:44

45:55

3

5c

THF

14

64:36

40:60

4

5d

THF

11

58:42

47:53

5

5e

THF

<5

NAd

NAd

6

5f

THF

11

52:48

63:37

7

5g

THF

32

83:17

33:67

8

5h

THF

92

>95:5

97:3

9

5i

THF

44

>95:5

96:4

10

5j

THF

17

87:13

13:87

11

5h

CH2Cl2

<5

NAd

NAd

12

5h

DMSO

37

>95:5

62:38

13

5h

DMF

58

>95:5

94:6

14

5h

MeCN

70

>95:5

94:6

15

5h

MeOH

21

>95:5

50:50

16

5h

toluene

75

>95:5

96:4

17e

5h

THF

92

>95:5

97:3

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  1. Reactions were conducted in the presence of CoCl2 (10 mol %), 5h (10 mol %), 4CzlPN (2.0 mol %), i-Pr2NEt (20 mol %), 1a (1.5 equiv), 2a (1.0 equiv) and 1.5 equiv Hantzsch’s ester (1.5 equiv) at 22 °C for 14 h.
  2. aYield of a mixture of diastereomers isolated.
  3. bDetermined by analysis of 1H NMR spectra of unpurified mixtures.
  4. cDetermined by analysis of HPLC spectra.
  5. dNot available.
  6. eThe reaction was performed in the presence of 5.0 mol % 5 h, 5.0 mol % CoCl2 and 1.0 mol % 4CzIPN. 4CzlPN = 1,2,3,5-tetrakis(carbazole-9-yl)−4,6-dicyanobenzene, Hantzsch’s ester = diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate.
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