Table 1 Optimization of conditions for reaction of enol silyl ether 1a with benzalmalononitrile (2a)

From: Direct allylic C–H alkylation of enol silyl ethers enabled by photoredox–Brønsted base hybrid catalysis

View full size image

Entry

4

Base (mol%)

d.r.a

Yield (%)b

1

4a

2,4,6-collidine (100)

1.7:1

78

2

4a

DTBMP (100)

1.7:1

27

3

4a

K3PO4 (100)

–

0

4

4b

2,4,6-collidine (100)

1.7:1

14

5

4c

2,4,6-collidine (100)

–

0

6c

4a

2,4,6-collidine (100)

2.0:1

89

7c

4a

2,4,6-collidine (10)

1.9:1

78

8d

4a

2,4,6-collidine (10)

2.0:1

95 (98)

9e

4a

2,4,6-collidine (10)

1.8:1

(96)

  1. Unless otherwise noted, the reactions were performed with 1a (0.1 mmol), 2a (1.2 equiv), base and 4 (2 mol%) in MeCN (1.0 mL) at 25 °C for 12 h under argon atmosphere with light irradiation (blue LED, 750 W m−2)
  2. 1H NMR proton nuclear magnetic resonance, d.r. diastereomeric ratios, LED light-emitting diode, DTBMP 2,6-di-tert-butyl-4-methylpyridine, TBS  t-butyldimethylsilyl, DCE 1,2-dichloroethane
  3. aDetermined by 1H NMR from crude reaction mixture
  4. bNMR yield with mesitylene as an internal standard. The value within parentheses is an isolated yield
  5. cThe reaction was conducted in DCE (1.0 mL)
  6. dIn DCE (0.5 mL)
  7. eCarried out with 1a (2.0  mmol, 0.42 g), 2a (1.1 equiv), 2,4,6-collidine (10 mol%) and 4a (0.5 mol%) in DCE (10 mL) at 25  °C for 18 h under argon atmosphere with light irradiation (blue LEDs, total 5000 W m−2)
Back to article page